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Sample records for warroad mn babb

  1. Warroad, MN Natural Gas Exports to Canada

    Annual Energy Outlook [U.S. Energy Information Administration (EIA)]

    Thousand Cubic Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 2000's -- -- -- 2010's -- 4.71 3.42 5.16 5.77 3.58 Thousand Cubic Feet)

    Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 7.73 6.52 5.03 4.85 4.94 5.07 5.04 4.58 4.38 3.99 4.09 4.11 2012 4.13 3.39 2.83 2.48 2.67 2.78 3.36 3.31 3.20 3.82 5.22 4.65 2013 6.75 7.39 5.25 5.00 4.66 4.28 4.37 3.99 4.00 3.98 4.28 7.05 2014 20.09 17.10 11.65 4.88 4.55 4.59 4.06 3.63 3.62 3.42 5.20 3.86

  2. Warroad, MN Natural Gas Exports to Canada

    Annual Energy Outlook [U.S. Energy Information Administration (EIA)]

    Annual Download Series History Download Series History Definitions, Sources & Notes Definitions, Sources & Notes Show Data By: Data Series Area 1999 2000 2001 2002 2003 View...

  3. U.S. Natural Gas Exports to Mexico

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    MI St. Clair, MI Noyes, MN Warroad, MN Babb, MT Havre, MT Port of Morgan, MT Sherwood, ND Pittsburg, NH Buffalo, NY Grand Island, NY Massena, NY Niagara Falls, NY Waddington, NY...

  4. Warroad, MN Natural Gas Imports by Pipeline from Canada

    Gasoline and Diesel Fuel Update (EIA)

    4,325 4,551 4,610 4,835 3,997 3,968 1996-2015 Pipeline Prices 4.69 4.17 3.06 3.94 5.95 3.32

  5. Warroad, MN Natural Gas Pipeline Imports From Canada (Million...

    Annual Energy Outlook [U.S. Energy Information Administration (EIA)]

    Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 523 453 478 390 267 292 275 281 291 358 428 515 2012 506 516 388 379 286 272 286 284 405 366 420 501 2013 599 549 511 452...

  6. Warroad, MN Natural Gas Pipeline Imports From Canada (Dollars...

    U.S. Energy Information Administration (EIA) Indexed Site

    Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 1990's 2.14 2.22 1.71 2.06 2000's 3.95 4.52 3.16 5.63 6.15 8.28 7.94 6.75 8.50 4.24 2010's 4.69 4.17 ...

  7. Warroad, MN Natural Gas Pipeline Imports From Canada (Million...

    U.S. Energy Information Administration (EIA) Indexed Site

    Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 523 453 478 390 267 292 275 281 291 358 428 515 2012 506 516 388 379 286 272 286 284 405 366 420 501 2013 599 549 511 452 ...

  8. Warroad, MN Natural Gas Pipeline Imports From Canada (Million...

    U.S. Energy Information Administration (EIA) Indexed Site

    Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 1990's 685 512 473 412 2000's 4,576 5,318 5,374 4,925 4,793 4,982 3,563 4,813 4,800 4,380 2010's 4,325 ...

  9. Warroad, MN Natural Gas Pipeline Exports to Canada (Million Cubic...

    U.S. Energy Information Administration (EIA) Indexed Site

    to Canada (Million Cubic Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 1990's NA 2000's NA NA NA 0 - No Data Reported; -- Not Applicable; ...

  10. Warroad, MN Natural Gas Pipeline Imports From Canada (Dollars...

    U.S. Energy Information Administration (EIA) Indexed Site

    Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 4.43 4.38 3.98 4.41 4.60 4.56 4.54 4.50 4.06 3.88 3.71 3.57 2012 3.23 2.86 2.57 2.21 2.23 2.51 3.12 3.07 2.85 3.29 3.95 ...

  11. Warroad, MN Natural Gas Pipeline Exports (Price) Canada (Dollars...

    U.S. Energy Information Administration (EIA) Indexed Site

    (Price) Canada (Dollars per Thousand Cubic Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 1990's NA 2000's NA NA NA - No Data Reported; -- ...

  12. Price of Babb, MT Liquefied Natural Gas Exports to Canada (Dollars...

    Annual Energy Outlook [U.S. Energy Information Administration (EIA)]

    Babb, MT Liquefied Natural Gas Exports to Canada (Dollars per Thousand Cubic Feet) Price of Babb, MT Liquefied Natural Gas Exports to Canada (Dollars per Thousand Cubic Feet) Year...

  13. Babb, MT Liquefied Natural Gas Exports (Million Cubic Feet)

    U.S. Energy Information Administration (EIA) Indexed Site

    (Million Cubic Feet) Babb, MT Liquefied Natural Gas Exports (Million Cubic Feet) Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2015 5 - = No Data Reported; -- = Not Applicable; NA = Not Available; W = Withheld to avoid disclosure of individual company data. Release Date: 08/31/2016 Next Release Date: 09/30/2016 Referring Pages: U.S.

  14. Babb, MT Liquefied Natural Gas Exports to Canada (Million Cubic Feet)

    U.S. Energy Information Administration (EIA) Indexed Site

    Liquefied Natural Gas Exports to Canada (Million Cubic Feet) Babb, MT Liquefied Natural Gas Exports to Canada (Million Cubic Feet) Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2015 5 - = No Data Reported; -- = Not Applicable; NA = Not Available; W = Withheld to avoid disclosure of individual company data. Release Date: 08/31/2016 Next Release Date: 09/30/2016 Referring Pages: U.S. Liquefied Natural Gas

  15. U.S. Total Imports

    U.S. Energy Information Administration (EIA) Indexed Site

    St. Clair, MI International Falls, MN Noyes, MN Warroad, MN Babb, MT Havre, MT Port of Del Bonita, MT Port of Morgan, MT Sweetgrass, MT Whitlash, MT Portal, ND Sherwood, ND Pittsburg, NH Champlain, NY Grand Island, NY Massena, NY Niagara Falls, NY Waddington, NY Sumas, WA Highgate Springs, VT North Troy, VT U.S. Pipeline Total from Mexico Ogilby, CA Otay Mesa, CA Alamo, TX El Paso, TX Galvan Ranch, TX Hidalgo, TX McAllen, TX Penitas, TX LNG Imports from Algeria Cove Point, MD Everett, MA Lake

  16. U.S. Natural Gas Imports by Pipeline from Mexico

    Annual Energy Outlook [U.S. Energy Information Administration (EIA)]

    St. Clair, MI International Falls, MN Noyes, MN Warroad, MN Babb, MT Havre, MT Port of Del Bonita, MT Port of Morgan, MT Sweetgrass, MT Whitlash, MT Portal, ND Sherwood, ND Pittsburg, NH Champlain, NY Grand Island, NY Massena, NY Niagara Falls, NY Waddington, NY Sumas, WA Highgate Springs, VT North Troy, VT U.S. Pipeline Total from Mexico Ogilby, CA Otay Mesa, CA Alamo, TX El Paso, TX Galvan Ranch, TX Hidalgo, TX McAllen, TX Penitas, TX LNG Imports from Algeria Cove Point, MD Everett, MA Lake

  17. U.S. Total Exports

    U.S. Energy Information Administration (EIA) Indexed Site

    Barbados Total To Brazil Freeport, TX Sabine Pass, LA Total to Canada Eastport, ID Calais, ME Detroit, MI Marysville, MI Port Huron, MI Crosby, ND Portal, ND Sault St. Marie, MI St. Clair, MI Noyes, MN Warroad, MN Babb, MT Havre, MT Port of Morgan, MT Sherwood, ND Pittsburg, NH Buffalo, NY Grand Island, NY Massena, NY Niagara Falls, NY Waddington, NY Sumas, WA Sweetgrass, MT Total to Chile Sabine Pass, LA Total to China Kenai, AK Sabine Pass, LA Total to Egypt Freeport, TX Total to India

  18. U.S. Natural Gas Imports by Pipeline from Canada

    Annual Energy Outlook [U.S. Energy Information Administration (EIA)]

    Barbados Total To Brazil Freeport, TX Sabine Pass, LA Total to Canada Eastport, ID Calais, ME Detroit, MI Marysville, MI Port Huron, MI Crosby, ND Portal, ND Sault St. Marie, MI St. Clair, MI Noyes, MN Warroad, MN Babb, MT Havre, MT Port of Morgan, MT Sherwood, ND Pittsburg, NH Buffalo, NY Grand Island, NY Massena, NY Niagara Falls, NY Waddington, NY Sumas, WA Sweetgrass, MT Total to Chile Sabine Pass, LA Total to China Kenai, AK Sabine Pass, LA Total to Egypt Freeport, TX Total to India

  19. babb-99.PDF

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    b-61 NNSA, Air Force Complete Successful B61-12 Life Extension Program Development Flight Test at Tonopah Test Range WASHINGTON - The National Nuclear Security Administration (NNSA) and United States Air Force completed the third development flight test of a non-nuclear B61-12 nuclear gravity bomb at Tonopah Test Range in Nevada on October 20, 2015. "This demonstration of effective end-to-end system... NNSA, Air Force Complete Successful B61-12 Life Extension Program Development Flight Test

  20. Babb, MT Natural Gas Export to Canada

    Gasoline and Diesel Fuel Update (EIA)

    6,702 6,671 12,807 15,525 17,235 17,421 1996-2014 Pipeline Prices 3.26 3.86 3.98 2.47 3.13 4.05 1996...

  1. Babb, MT Natural Gas Export to Canada

    Gasoline and Diesel Fuel Update (EIA)

    96 9.53 10.72 10.55 12.56 15.35 1989-2016 Florida 16.78 16.00 17.06 17.83 20.52 22.40 1989-2016 Georgia 10.79 10.94 13.01 16.48 20.53 24.74 1989-2016 Maryland 9.95 9.46 11.04 NA 12.66 16.06 1989-2016 Michigan 7.25 7.58 7.80 7.71 9.56 12.33 1989-2016 New Jersey 6.55 6.86 8.24 8.99 9.49 10.78 1989-2016 New York 10.31 9.45 9.65 9.90 10.91 14.77 1989-2016 Ohio 6.48 6.44 7.16 8.01 11.73 19.29 1989-2016 Pennsylvania 8.75 8.64 9.51 9.91 11.30 15.62 1989-2016 Virginia 9.45 8.76 10.20 10.63 12.69 15.51

  2. Team OptiMN

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    University of Minnesota Team OptiMN "OptiMN Impact Home" Project Summary Designed to fit on the majority of North Minneapolis infill lots, the OptiMN Impact Home is a collaborative project between the University of Minnesota and Urban Homeworks. The overarching goal was a flexible, high-performance, energy-efficient, and affordable house that can be easily built by Urban Homeworks and purchased by eligible low-income residents of North Minneapolis through the Green Homes North program.

  3. MN Office of Energy Security | Open Energy Information

    Open Energy Info (EERE)

    MN Office of Energy Security Jump to: navigation, search Name: MN Office of Energy Security Place: St. Paul, MN Website: www.mnofficeofenergysecurity.c References: MN Office of...

  4. Category:Minneapolis, MN | Open Energy Information

    Open Energy Info (EERE)

    16 total. SVFullServiceRestaurant Minneapolis MN Northern States Power Co (Minnesota) Excel Energy.png SVFullServiceRestauran... 89 KB SVHospital Minneapolis MN Northern States...

  5. Babb, MT Natural Gas Imports by Pipeline from Canada

    Gasoline and Diesel Fuel Update (EIA)

    6,671 12,807 15,525 17,235 17,421 20,708 1996-2015 Pipeline Prices 3.86 3.98 2.47 3.13 4.05 2.34 1996

  6. Mn4+ emission in pyrochlore oxides

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Du, Mao-Hua

    2015-01-01

    For the existing Mn4+ activated red phosphors have relatively low emission energies (or long emission wavelengths) and are therefore inefficient for general lighting. Density functional calculations are performed to study Mn4+ emission in rare-earth hafnate, zirconate, and stannate pyrochlore oxides (RE2Hf2O7, RE2Zr2O7, and RE2Sn2O7). We show how the different sizes of the RE3+ cation in these pyrochlores affect the local structure of the distorted MnO6 octahedron, the Mn–O hybridization, and the Mn4+ emission energy. The Mn4+ emission energies of many pyrochlores are found to be higher than those currently known for Mn4+ doped oxides and should be closer to thatmore » of Y2O3:Eu3+ (the current commercial red phosphor for fluorescent lighting). The O–Mn–O bond angle distortion in a MnO6 octahedron is shown to play an important role in weakening Mn–O hybridization and consequently increasing the Mn4+ emission energy. Our result shows that searching for materials that allow significant O–Mn–O bond angle distortion in a MnO6 octahedron is an effective approach to find new Mn4+ activated red phosphors with potential to replace the relatively expensive Y2O3:Eu3+ phosphor.« less

  7. CRAD, NNSA - Maintenance (MN) | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    NNSA - Maintenance (MN) CRAD, NNSA - Maintenance (MN) CRAD for Maintenance (MN). Criteria Review and Approach Documents (CRADs) that can be used to conduct a well-organized and thorough assessment of elements of safety and health programs. CRADs consist of a Performance Objective that identifies the expectation(s) or requirement(s) to be verified, which reflect the complete scope of the assessment; Criteria that provide specifics by which the performance objectives are measured, including

  8. DOE - Office of Legacy Management -- Elk River Reactor - MN 01

    Office of Legacy Management (LM)

    Elk River Reactor - MN 01 FUSRAP Considered Sites Site: Elk River Reactor (MN.01 ) Eliminated from consideration under FUSRAP - Reactor was dismantled and decommissioned by 1974 Designated Name: Not Designated Alternate Name: None Location: Elk River , Minnesota MN.01-1 Evaluation Year: 1985 MN.01-1 Site Operations: Boiling water reactor demonstration, research and development program MN.01-1 Site Disposition: Eliminated MN.01-1 Radioactive Materials Handled: None Indicated Primary Radioactive

  9. Magnetostructural phase transformations in Tb 1-x Mn 2 (Journal...

    Office of Scientific and Technical Information (OSTI)

    phase transformations in Tb 1-x Mn 2 Citation Details In-Document Search Title: Magnetostructural phase transformations in Tb 1-x Mn 2 Magnetism and phase transformations ...

  10. Magnetocrystalline anisotropy in UMn<mn>2mn>Ge>2mn> and related Mn-based actinide ferromagnets

    SciTech Connect (OSTI)

    Parker, David S.; Ghimire, Nirmal; Singleton, John; Thompson, J. D.; Bauer, Eric D.; Baumbach, Ryan; Mandrus, David; Li, Ling; Singh, David J.

    2015-05-04

    We present magnetization isotherms in pulsed magnetic fields up to 62 Tesla, supported by first principles calculations, demonstrating a huge uniaxial magnetocrystalline anisotropy energy - approximately 20 MJ/m3 - in UMn<mn>2mn>Ge>2mn>. This large anisotropy results from the extremely strong spin-orbit coupling affecting the uranium 5 f electrons, which in the calculations exhibit a substantial orbital moment exceeding 2 μB. Finally, we also find from theoretical calculations that a number of isostructural Mn-actinide compounds are expected to have similarly large anisotropy.

  11. Magnetic coupling in ferromagnetic semiconductor (Ga,Mn)As/(Al,Ga,Mn)As bilayers

    SciTech Connect (OSTI)

    Wang, M.; Wadley, P.; Campion, R. P.; Rushforth, A. W.; Edmonds, K. W.; Gallagher, B. L.; Charlton, T. R.; Kinane, C. J.; Langridge, S.

    2015-08-07

    We report on a study of ferromagnetic semiconductor (Ga,Mn)As/(Al,Ga,Mn)As bilayers using magnetometry and polarized neutron reflectivity (PNR). From depth-resolved characterization of the magnetic structure obtained by PNR, we concluded that the (Ga,Mn)As and (Al,Ga,Mn)As layers have in-plane and perpendicular-to-plane magnetic easy axes, respectively, with weak interlayer coupling. Therefore, the layer magnetizations align perpendicular to each other under low magnetic fields and parallel at high fields.

  12. SSL Demonstration: Bridge Lighting, Minneapolis, MN

    SciTech Connect (OSTI)

    2014-10-01

    DOE Solid-State Lighting GATEWAY summary brief for Phase II report on the longer-term performance of LED lighting installed in 2008 on the I-35W Bridge in Minneapolis, MN.

  13. High Mn austenitic stainless steel

    DOE Patents [OSTI]

    Yamamoto, Yukinori [Oak Ridge, TN; Santella, Michael L [Knoxville, TN; Brady, Michael P [Oak Ridge, TN; Maziasz, Philip J [Oak Ridge, TN; Liu, Chain-tsuan [Knoxville, TN

    2010-07-13

    An austenitic stainless steel alloy includes, in weight percent: >4 to 15 Mn; 8 to 15 Ni; 14 to 16 Cr; 2.4 to 3 Al; 0.4 to 1 total of at least one of Nb and Ta; 0.05 to 0.2 C; 0.01 to 0.02 B; no more than 0.3 of combined Ti+V; up to 3 Mo; up to 3 Co; up to 1W; up to 3 Cu; up to 1 Si; up to 0.05 P; up to 1 total of at least one of Y, La, Ce, Hf, and Zr; less than 0.05 N; and base Fe, wherein the weight percent Fe is greater than the weight percent Ni, and wherein the alloy forms an external continuous scale including alumina, nanometer scale sized particles distributed throughout the microstructure, the particles including at least one of NbC and TaC, and a stable essentially single phase FCC austenitic matrix microstructure that is essentially delta-ferrite-free and essentially BCC-phase-free.

  14. Local environment of Mn in Mn delta-doped Si layers

    SciTech Connect (OSTI)

    Xiao, Q.F.; Kahwaji, S.; Monchesky, T.L.; Gordon, R.A.; Crozier, E.D.

    2009-11-09

    Dilute magnetic semiconductors combine both magnetic ordering and semiconducting behaviour, leading to potential spintronic applications. Silicon containing dilute Mn impurities is a potential dilute magnetic semiconductor. We have grown Mn delta-doped films by deposition of 0.7 of a monolayer of Mn on Si(001) by molecular beam epitaxy and capping the film with Si. The magnetic properties are likely sensitive to the distribution of Mn on substitutional or interstitial sites and the formation of metallic precipitates. We have used polarization-dependent XAFS to examine the local structure. We compare to a thicker MnSi film grown on Si(111) and also examine the influence of lead on the manganese environment when used as a surfactant in the growth process.

  15. Structural, magnetic, and superconducting properties of pulsed-laser-deposition-grown La<mn>1.85mn> Sr<mn>0.15mn> CuO<mn>4mn> / La<mn>2mn>/>3mn> Ca<mn>1mn>/>3mn> MnO>3mn> superlattices on (001)-oriented LaSrAlO<mn>4mn> substrates

    SciTech Connect (OSTI)

    Das, S.; Sen, K.; Marozau, I.; Uribe-Laverde, M. A.; Biskup, N.; Varela, M.; Khaydukov, Y.; Soltwedel, O.; Keller, T.; Döbeli, M.; Schneider, C. W.; Bernhard, C.

    2014-03-12

    Epitaxial La<mn>1.85mn> Sr<mn>0.15mn> CuO<mn>4mn> / La<mn>2mn>/>3mn> Ca<mn>1mn>/>3mn> MnO>3mn> (LSCO/LCMO) superlattices (SL) on (001)- oriented LaSrAlO4 substrates have been grown with pulsed laser deposition (PLD) technique. Their structural, magnetic and superconducting properties have been determined with in-situ reflection high energy electron diffraction (RHEED), x-ray diffraction, specular neutron reflectometry, scanning transmission electron microscopy (STEM), electric transport, and magnetization measurements. We find that despite the large mismatch between the in-plane lattice parameters of LSCO (a = 0.3779 nm) and LCMO (a = 0.387 nm) these superlattices can be grown epitaxially and with a high crystalline quality. While the first LSCO layer remains clamped to the LSAO substrate, a sizeable strain relaxation occurs already in the first LCMO layer. The following LSCO and LCMO layers adopt a nearly balanced state in which the tensile and compressive strain effects yield alternating in-plane lattice parameters with an almost constant average value. No major defects are observed in the LSCO layers, while a significant number of vertical antiphase boundaries are found in the LCMO layers. The LSCO layers remain superconducting with a relatively high superconducting onset temperature of Tconset ≈ 36 K. The macroscopic superconducting response is also evident in the magnetization data due to a weak diamagnetic signal below 10 K for H ∥ ab and a sizeable paramagnetic shift for H ∥ c that can be explained in terms of a vortex-pinning-induced flux compression. The LCMO layers maintain a

  16. Properties of (Ga,Mn)As codoped with Li

    SciTech Connect (OSTI)

    Miyakozawa, Shohei; Chen, Lin; Matsukura, Fumihiro; Ohno, Hideo

    2014-06-02

    We grow Li codoped (Ga,Mn)As layers with nominal Mn composition up to 0.15 by molecular beam epitaxy. The layers before and after annealing are characterized by x-ray diffraction, transport, magnetization, and ferromagnetic resonance measurements. The codoping with Li reduces the lattice constant and electrical resistivity of (Ga,Mn)As after annealing. We find that (Ga,Mn)As:Li takes similar Curie temperature to that of (Ga,Mn)As, but with pronounced magnetic moments and in-plane magnetic anisotropy, indicating that the Li codoping has nontrivial effects on the magnetic properties of (Ga,Mn)As.

  17. Spin reorientation and Ce-Mn coupling in antiferromagnetic oxypnictide CeMnAsO

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zhang, Qiang; Tian, Wei; Peterson, Spencer G.; Dennis, Kevin W.; Vaknin, David

    2015-02-18

    Structure and magnetic properties of high-quality polycrystlline CeMnAsO, a parent compound of the “1111”-type oxypnictides, have been investigated using neutron powder diffraction and magnetization measurements. We find that CeMnAsO undergoes a C-type antiferromagnetic order with Mn2+(S = 5/2) moments pointing along the c axis below a relatively high Néel temperature of TN = 347(1) K. Below TSR = 35 K, two simultaneous transitions occur where the Mn moments reorient from the c axis to the ab plane preserving the C-type magnetic order, and Ce moments undergo long-range AFM ordering with antiparallel moments pointing in the ab plane. Another transition tomore » a noncollinear magnetic structure occurs below 7 K. The ordered moments of Mn and Ce at 2 K are 3.32(4) μB and 0.81(4)μB, respectively. We find that CeMnAsO primarily falls into the category of a local-moment antiferromagnetic insulator in which the nearest-neighbor interaction (J1) is dominant with J2 < J1/2 in the context of J1 – J2 – Jc model. The spin reorientation transition driven by the coupling between Ce and the transition metal seems to be common to Mn, Fe, and Cr ions, but not to Co and Ni ions in the isostructural oxypnictides. As a result, a schematic illustration of magnetic structures in Mn and Ce sublattices in CeMnAsO is presented.« less

  18. Magnetoelectric coupling tuned by competing anisotropies in Mn...

    Office of Scientific and Technical Information (OSTI)

    Magnetoelectric coupling tuned by competing anisotropies in Mn 1 - x Ni x TiO 3 Prev Next Title: Magnetoelectric coupling tuned by competing anisotropies in Mn 1 - x Ni x TiO ...

  19. Influence of interstitial Mn on magnetism in room-temperature ferromagnet Mn(1+delta)Sb

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Taylor, Alice E; Berlijn, Tom; Hahn, Steven E; May, Andrew F; Williams, Travis J; Poudel, Lekhanath N; Calder, Stuart A; Fishman, Randy Scott; Stone, Matthew B; Aczel, Adam A; et al

    2015-01-01

    We report elastic and inelastic neutron scattering measurements of the high-TC ferromagnet Mn(1+delta)Sb. Measurements were performed on a large, TC = 434 K, single crystal with interstitial Mn content of delta=0.13. The neutron diffraction results reveal that the interstitial Mn has a magnetic moment, and that it is aligned antiparallel to the main Mn moment. We perform density functional theory calculations including the interstitial Mn, and find the interstitial to be magnetic in agreement with the diffraction data. The inelastic neutron scattering measurements reveal two features in the magnetic dynamics: i) a spin-wave-like dispersion emanating from ferromagnetic Bragg positions (Hmore » K 2n), and ii) a broad, non-dispersive signal centered at forbidden Bragg positions (H K 2n+1). The inelastic spectrum cannot be modeled by simple linear spin-wave theory calculations, and appears to be significantly altered by the presence of the interstitial Mn ions. The results show that the influence of the int« less

  20. Influence of interstitial Mn on magnetism in room-temperature ferromagnet Mn(1+delta)Sb

    SciTech Connect (OSTI)

    Taylor, Alice E; Berlijn, Tom; Hahn, Steven E; May, Andrew F; Williams, Travis J; Poudel, Lekhanath N; Calder, Stuart A; Fishman, Randy Scott; Stone, Matthew B; Aczel, Adam A; Cao, Huibo; Lumsden, Mark D; Christianson, Andrew D

    2015-01-01

    We report elastic and inelastic neutron scattering measurements of the high-TC ferromagnet Mn(1+delta)Sb. Measurements were performed on a large, TC = 434 K, single crystal with interstitial Mn content of delta=0.13. The neutron diffraction results reveal that the interstitial Mn has a magnetic moment, and that it is aligned antiparallel to the main Mn moment. We perform density functional theory calculations including the interstitial Mn, and find the interstitial to be magnetic in agreement with the diffraction data. The inelastic neutron scattering measurements reveal two features in the magnetic dynamics: i) a spin-wave-like dispersion emanating from ferromagnetic Bragg positions (H K 2n), and ii) a broad, non-dispersive signal centered at forbidden Bragg positions (H K 2n+1). The inelastic spectrum cannot be modeled by simple linear spin-wave theory calculations, and appears to be significantly altered by the presence of the interstitial Mn ions. The results show that the influence of the int

  1. CaMn2Al10: Itinerant Mn magnetism on the verge of magnetic order

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Steinke, L.; Simonson, J. W.; Yin, W. -G.; Smith, G. J.; Kistner-Morris, J. J.; Zellman, S.; Puri, A.; Aronson, M. C.

    2015-07-24

    We report the discovery of CaMn2Al10, a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83μB/Mn, significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈ 9% of Rln2. These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010]/χ[001] ≈ 3.5. A strong power-lawmore » divergence χ(T) ~ T–1.2 below 20 K implies incipient ferromagnetic order, an Arrott plot analysis of the magnetization suggests a vanishing low Curie temperature TC ~ 0. Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.« less

  2. Opti-MN Impact House Presentation | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Opti-MN Impact House Presentation Opti-MN Impact House Presentation Opti-MN was the Grand Winner of the 2015 Race to Zero Student Design Competition. View the presentation for the Opti-MN Impact House below. Read a full list of the winning teams. Opti-MN Presentation (5.74 MB) More Documents & Publications 2015 Race to Zero Competition Grand Winner and Grand Winner Finalist Team Submissions 2016 Race to Zero Competition Winner Team Presentations 2014 Race to Zero Student Design Competition:

  3. Unexpected crystal and magnetic structures in MnCu4In and MnCu4Sn

    SciTech Connect (OSTI)

    Provino, A.; Paudyal, D.; Fornasini, ML; Dhiman, I.; Dhar, SK.; Das, A.; Mudryk, Y.; Manfrinetti, P.; Pecharsky, VK

    2013-01-29

    We discovered a new compound MnCu4In with its own hexagonal structure type (hP12-P63mc, ternary ordered derivative of the hexagonal MgZn2-type) that becomes ferromagnetic at TC = 540 K. This transition temperature is higher than that found in the MnCu2In and MnCu2Sn alloys. In contrast, the homologous compound MnCu4Sn, which crystallizes in the cubic MgCu4Sn-type, orders antiferromagnetically with TN = 110 K. The neutron diffraction studies show ferromagnetic spin orientation in the {1 0 1} plane in MnCu4In with a magnetic moment of 4.5 ?B/Mn at 22 K, and a corresponding value of 4.7 ?B/Mn in the antiferromagnetic MnCu4Sn with propagation vector View the MathML source. The first-principles electronic structure calculations show that the unexpected difference in both magnetic and crystal structures of MnCu4In and MnCu4Sn is due to the difference in the Mn-3d bands and exchange interactions relating to different crystal anisotropy, coordination numbers, and interatomic distances.

  4. Solid Solution Phases in the Olivine-Type LiMnPO4/MnPO4 System

    SciTech Connect (OSTI)

    Chen, Guoying; Richardson, Thomas J.

    2009-04-07

    Nonstoichiometry is reported in the LiMnPO{sub 4}/MnPO{sub 4} system for the first time. As lithium is removed from crystalline LiMnPO{sub 4} by chemical or electrochemical methods, the resulting two phase mixture consists of stoichiometric LiMnPO{sub 4} and a delithiated phase, Li{sub y}MnPO{sub 4}, whose lattice parameters depend upon the global extent of delithiation and on the crystalline domain size of the delithiated phase. This behavior is reproduced during electrochemical insertion of lithium. Again, no evidence for nonstoichiometry was found in the vicinity of LiMnPO{sub 4}. Attempts to create single phase solid solutions by heating mixtures of the two phases failed due to the thermal instability of Li{sub y}MnPO{sub 4}.

  5. Investigations of element spatial correlation in Mn-promoted...

    Office of Scientific and Technical Information (OSTI)

    Investigations of element spatial correlation in Mn-promoted Co-based Fischer-Tropsch synthesis catalysts This content will become publicly available on June 4, 2017 Title: ...

  6. Microsoft Word - MnO_Reduction bh

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    May 2016 Figure 1. Schematic of flow-through system developed at SSRL. A reaction vessel with manganese oxides and media required for microbial experiments was kept anoxic with nitrogen gas and pH was measured using an environmental pH probe. A portion of the fluid was sampled using a peristaltic pump through anaerobic tubing to the beam line hutch where the x-ray beam sampled the Mn coordination environment, mineralogy, and redox state through a Kapton tape window on an x-ray flow-through cell.

  7. Spin caloritronics in graphene with Mn

    SciTech Connect (OSTI)

    Torres, Alberto Lima, Matheus P. Fazzio, A.; Silva, Antnio J. R. da

    2014-02-17

    We show that graphene with Mn adatoms trapped at single vacancies features spin-dependent Seebeck effect, thus enabling the use of this material for spin caloritronics. A gate potential can be used to tune its thermoelectric properties in a way it presents either a total spin polarized current, flowing in one given direction, or currents for both spins flowing in opposite directions without net charge transport. Moreover, we show that the thermal magnetoresistance can be tuned between ?100% and +100% by varying a gate potential.

  8. Magnetic Moment Enhancement for Mn7 Cluster on Graphene

    SciTech Connect (OSTI)

    Liu, Xiaojie; Wang, Cai-Zhuang; Lin, Hai-Qing; Ho, Kai-Ming

    2014-08-21

    Mn7 cluster on graphene with different structural motifs and magnetic orders are investigated systematically by first-principles calculations. The calculations show that Mn7 on graphene prefers a two-layer motif and exhibits a ferrimagnetic coupling. The magnetic moment of the Mn7 cluster increases from 5.0 ?B at its free-standing state to about 6.0 ?B upon adsorption on graphene. Mn7 cluster also induces about 0.3 ?B of magnetic moment in the graphene layer, leading to an overall enhancement of 1.3 ?B magnetic moment for Mn7 on graphene. Detail electron transfer and bonding analysis have been carried out to investigate the origin of the magnetic enhancement.

  9. Mn4+ emission in pyrochlore oxides

    SciTech Connect (OSTI)

    Du, Mao-Hua

    2015-01-01

    For the existing Mn4+ activated red phosphors have relatively low emission energies (or long emission wavelengths) and are therefore inefficient for general lighting. Density functional calculations are performed to study Mn4+ emission in rare-earth hafnate, zirconate, and stannate pyrochlore oxides (RE2Hf2O7, RE2Zr2O7, and RE2Sn2O7). We show how the different sizes of the RE3+ cation in these pyrochlores affect the local structure of the distorted MnO6 octahedron, the Mn–O hybridization, and the Mn4+ emission energy. The Mn4+ emission energies of many pyrochlores are found to be higher than those currently known for Mn4+ doped oxides and should be closer to that of Y2O3:Eu3+ (the current commercial red phosphor for fluorescent lighting). The O–Mn–O bond angle distortion in a MnO6 octahedron is shown to play an important role in weakening Mn–O hybridization and consequently increasing the Mn4+ emission energy. Our result shows that searching for materials that allow significant O–Mn–O bond angle distortion in a MnO6 octahedron is an effective approach to find new Mn4+ activated red phosphors with potential to replace the relatively expensive Y2O3:Eu3+ phosphor.

  10. Electrochemical behavior of β-MnO{sub 2} and MnOOH nanorods in different electrolytes

    SciTech Connect (OSTI)

    Chinnasamy, Revathi; Thangavelu, Rajendrakumar Ramasamy

    2015-06-24

    A manganese dioxide (β-MnO{sub 2}) and MnOOH nanoparticles has been synthesized by hydrothermal method. As prepared samples are analyzed by X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). FESEM showed rod morphology within the diameter of 50–200 and length of few nanometers. These nanorods are immobilized on a Glassy Carbon Electrode (GCE) by drop cast method. The comparative electrochemical behavior of β-MnO{sub 2} and MnOOH rod modified GCE electrodes are analyzed by cyclic Voltammetry (CV) method in different electrolytes of 0.1M KCl, 0.1M Na{sub 2}SO{sub 4}, 0.1M NaOH, 0.1M PBS, 0.1M H{sub 2}SO{sub 4}. From the cyclic Voltammetry analysis found that in all the electrolytes both β-MnO{sub 2} and MnOOH modified GCE electrodes exhibit electrochemical behavior and KCl shows well redox properties as compared with others. There is also an observable difference in reduction potential value of both crystalline nanostructurers and concluded that β-MnO{sub 2} has high catalytic ability as compared with MnOOH rods.

  11. Babb, MT Natural Gas Pipeline Exports to Canada (Million Cubic Feet)

    Gasoline and Diesel Fuel Update (EIA)

    Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 1990's 1.53 NA NA 2000's NA 3.55 2.28 6.48 4.98 -- -- -- -- -- 2010's -- 3.39 -- -- 4.90 Feet)

    Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 3.39 2014 3.99 5.46

    Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 20 2014 47 75

  12. Babb, MT Natural Gas Pipeline Imports From Canada (Million Cubic Feet)

    Gasoline and Diesel Fuel Update (EIA)

    Cubic Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 1990's 1.16 1.40 1.65 2.00 2000's 5.83 2.74 2.24 4.70 5.21 7.32 5.44 6.46 7.49 3.26 2010's 3.86 3.98 2.47 3.13 4.05 2.34 Cubic Feet)

    Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 4.21 4.18 4.17 4.17 4.23 4.30 4.08 3.91 3.82 3.40 3.25 3.12 2012 2.71 2.22 1.93 1.85 2.18 2.02 2.46 2.36 2.50 3.31 3.50 3.33 2013 3.08 3.11 3.45 3.66 3.74 3.45 2.94 2.65 2.44 3.17 3.38 3.68 2014 3.79 4.94 5.31

  13. Babb, MT Liquefied Natural Gas Exports Price (Dollars per Thousand Cubic

    U.S. Energy Information Administration (EIA) Indexed Site

    Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 2010's

  14. Babb, MT Liquefied Natural Gas Exports Price (Dollars per Thousand Cubic

    U.S. Energy Information Administration (EIA) Indexed Site

    Feet) Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2015

  15. Babb, MT Natural Gas Pipeline Exports to Canada (Dollars per Thousand Cubic

    U.S. Energy Information Administration (EIA) Indexed Site

    Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 1990's 1.53 NA NA 2000's NA 3.55 2.28 6.48 4.98 -- -- -- -- -- 2010's -- 3.39 -- -- 4.90

  16. Babb, MT Natural Gas Pipeline Exports to Canada (Dollars per Thousand Cubic

    U.S. Energy Information Administration (EIA) Indexed Site

    Feet) Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 3.39 2014 3.99 5.46

  17. Babb, MT Natural Gas Pipeline Exports to Canada (Million Cubic Feet)

    U.S. Energy Information Administration (EIA) Indexed Site

    Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 1990's 91 NA NA 2000's NA 549 143 38 1,429 0 0 0 0 0 2010's 0 20 0 0 122

  18. Babb, MT Natural Gas Pipeline Exports to Canada (Million Cubic Feet)

    U.S. Energy Information Administration (EIA) Indexed Site

    Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 20 2014 47 75

  19. Babb, MT Natural Gas Pipeline Imports From Canada (Dollars per Thousand

    U.S. Energy Information Administration (EIA) Indexed Site

    Cubic Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 1990's 1.16 1.40 1.65 2.00 2000's 5.83 2.74 2.24 4.70 5.21 7.32 5.44 6.46 7.49 3.26 2010's 3.86 3.98 2.47 3.13 4.05 2.34

  20. Babb, MT Natural Gas Pipeline Imports From Canada (Dollars per Thousand

    U.S. Energy Information Administration (EIA) Indexed Site

    Cubic Feet) Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 4.21 4.18 4.17 4.17 4.23 4.30 4.08 3.91 3.82 3.40 3.25 3.12 2012 2.71 2.22 1.93 1.85 2.18 2.02 2.46 2.36 2.50 3.31 3.50 3.33 2013 3.08 3.11 3.45 3.66 3.74 3.45 2.94 2.65 2.44 3.17 3.38 3.68 2014 3.79 4.94 5.31 4.37 4.29 4.34 4.05 3.73 3.75 3.53 3.58 3.06 2015 2.67 2.46 2.28 2.30 2.53 2.42 2.47 2.46 2.41 2.03 2.21 1.92 2016 1.78 1.42 1.16 1.05 1.08 1.61

  1. Babb, MT Natural Gas Pipeline Imports From Canada (Million Cubic Feet)

    U.S. Energy Information Administration (EIA) Indexed Site

    Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 1990's 16,545 18,477 17,776 3,841 2000's 295 2,571 6,326 4,645 4,333 396 7,343 4,580 4,057 6,702 2010's 6,671 12,807 15,525 17,235 17,421 20,708

  2. Babb, MT Natural Gas Pipeline Imports From Canada (Million Cubic Feet)

    U.S. Energy Information Administration (EIA) Indexed Site

    Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 10 164 251 1,367 1,953 1,897 1,872 2,240 1,262 884 623 285 2012 217 406 580 1,533 1,373 2,243 2,223 1,846 1,913 1,680 867 642 2013 359 477 1,016 1,028 931 1,946 2,200 2,103 2,386 2,610 1,073 1,107 2014 966 835 945 1,817 2,587 2,030 1,931 1,322 1,076 1,162 1,070 1,680 2015 1,205 1,117 1,480 1,951 1,816 1,851 2,155 2,344 1,804 1,898 1,313 1,774 2016 1,621 1,411 1,102 2,572 3,062 2,603

  3. Price of Babb, MT Liquefied Natural Gas Exports to Canada (Dollars per

    U.S. Energy Information Administration (EIA) Indexed Site

    Thousand Cubic Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 2010's

  4. Inverse spin Hall effect in Pt/(Ga,Mn)As

    SciTech Connect (OSTI)

    Nakayama, H.; Chen, L.; Chang, H. W.; Ohno, H.; Matsukura, F.

    2015-06-01

    We investigate dc voltages under ferromagnetic resonance in a Pt/(Ga,Mn)As bilayer structure. A part of the observed dc voltage is shown to originate from the inverse spin Hall effect. The sign of the inverse spin Hall voltage is the same as that in Py/Pt bilayer structure, even though the stacking order of ferromagnetic and nonmagnetic layers is opposite to each other. The spin mixing conductance at the Pt/(Ga,Mn)As interface is determined to be of the order of 10{sup 19 }m{sup −2}, which is about ten times greater than that of (Ga,Mn)As/p-GaAs.

  5. DOE - Office of Legacy Management -- Twin Cities Ammunition - MN 0-01

    Office of Legacy Management (LM)

    Twin Cities Ammunition - MN 0-01 FUSRAP Considered Sites Site: TWIN CITIES AMMUNITION (MN.0-01) Eliminated from further consideration under FUSRAP - Referred to DOD Designated Name: Not Designated Alternate Name: None Location: New Brighton , Minnesota MN.0-01-1 Evaluation Year: 1987 MN.0-01-2 Site Operations: Site was formerly licensed under 10CFR 70 by the NRC. MN.0-01-1 MN.0-01-2 Site Disposition: Eliminated - No Authority - Referred to DOD MN.0-01-1 Radioactive Materials Handled: None

  6. Magnetic domain tuning and the emergence of bubble domains in the bilayer manganite La<mn>2mn>->2mn>xSr<mn>1mn>+>2mn>xMn>2mn>O>7mn>(x=<mn>0.32mn>)

    SciTech Connect (OSTI)

    Jeong, Juyoung; Yang, Ilkyu; Yang, Jinho; Ayala-Valenzuela, Oscar E.; Wulferding, Dirk; Zhou, J. -S.; Goodenough, John B.; de Lozanne, Alex; Mitchell, J. F.; Leon, Neliza; Movshovich, Roman; Jeong, Yoon Hee; Yeom, Han Woong; Kim, Jeehoon

    2015-08-17

    Here, we report a magnetic force microscopy study of the magnetic domain evolution in the layered manganite La2–2xSr1+2xMn2O7 (with x = 0.32). This strongly correlated electron compound is known to exhibit a wide range of magnetic phases, including a recently uncovered biskyrmion phase. We observe a continuous transition from dendritic to stripelike domains, followed by the formation of magnetic bubbles due to a field- and temperature-dependent competition between in-plane and out-of-plane spin alignments. The magnetic bubble phase appears at comparable field and temperature ranges as the biskyrmion phase, suggesting a close relation between both phases. Based on our real-space images we construct a temperature-field phase diagram for this composition.

  7. CaMn2Al10: Itinerant Mn magnetism on the verge of magnetic order

    SciTech Connect (OSTI)

    Steinke, L.; Simonson, J. W.; Yin, W. -G.; Smith, G. J.; Kistner-Morris, J. J.; Zellman, S.; Puri, A.; Aronson, M. C.

    2015-07-24

    We report the discovery of CaMn2Al10, a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83μB/Mn, significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈ 9% of Rln2. These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010][001] ≈ 3.5. A strong power-law divergence χ(T) ~ T–1.2 below 20 K implies incipient ferromagnetic order, an Arrott plot analysis of the magnetization suggests a vanishing low Curie temperature TC ~ 0. Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.

  8. Strong enhancement of s -wave superconductivity near a quantum critical point of Ca<mn>3mn>Ir>4mn>Sn>13mn>

    SciTech Connect (OSTI)

    Biswas, P. K.; Guguchia, Z.; Khasanov, R.; Chinotti, M.; Li, L.; Wang, Kefeng; Petrovic, C.; Morenzoni, E.

    2015-11-11

    We report microscopic studies by muon spin rotation/relaxation as a function of pressure of the Ca<mn>3mn>Ir>4mn>Sn>13mn> and Sr3Ir4Sn13 system displaying superconductivity and a structural phase transition associated with the formation of a charge density wave (CDW). Our findings show a strong enhancement of the superfluid density and a dramatic increase of the pairing strength above a pressure of ≈ 1.6 GPa giving direct evidence of the presence of a quantum critical point separating a superconducting phase coexisting with CDW from a pure superconducting phase. The superconducting order parameter in both phases has the same s-wave symmetry. In spite of the conventional phonon-mediated BCS character of the weakly correlated (Ca1-xSrx)3Ir4Sn13 system the dependence of the effective superfluid density on the critical temperature puts this compound in the “Uemura” plot close to unconventional superconductors. This system exemplifies that conventional BCS superconductors in the presence of competing orders or multi-band structure can also display characteristics of unconventional superconductors.

  9. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOE Patents [OSTI]

    Brager, Howard R.; Garner, Francis A.

    1987-01-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  10. Structure and magnetic properties of LnMnSbO ( Ln=La and Ce)

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zhang, Qiang; Kumar, C. M. N.; Tian, Wei; Dennis, Kevin W.; Goldman, Alan I.; Vaknin, David

    2016-03-11

    Here, a neutron powder diffraction (NPD) study of LnMnSbO (Ln = La or Ce) reveals differences between the magnetic ground state of the two compounds due to the strong Ce-Mn coupling compared to La-Mn. The two compounds adopt the P4/nmm space group down to 2 K, and whereas magnetization measurements do not show obvious anomaly at high temperatures, NPD reveals a C-type antiferromagnetic (AFM) order below TN = 255K for LaMnSbO and 240 K for CeMnSbO. While the magnetic structure of LaMnSbO is preserved to base temperature, a sharp transition at TSR = 4.5K is observed in CeMnSbO due tomore » a spin-reorientation (SR) transition of the Mn2+ magnetic moments from pointing along the c axis to the ab plane. The SR transition in CeMnSbO is accompanied by a simultaneous long-range AFM ordering of the Ce moments, which indicates that the Mn SR transition is driven by the Ce-Mn coupling. The ordered moments are found to be somewhat smaller than those expected for Mn2+ (S = 5/2) in insulators, but large enough to suggest that these compounds belong to the class of local-moment antiferromagnets. The lower TN found in these two compounds compared to the As-based counterparts (TN = 317 for LaMnAsO, TN = 347K for CeMnAsO) indicates that the Mn-Pn (Pn=As or Sb) hybridization that mediates the superexchange Mn-Pn-Mn coupling is weaker for the Sb-based compounds.« less

  11. Revealing the Restructured Surface of Li[Mn2]O4

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Amos, Charles D.; Roldan, Manuel A.; Varela, Maria; Goodenough, John B.; Ferreira, Paulo J.

    2016-03-29

    The spinel Revealing the Restructured Surface of Li[Mn2]O4 is a candidate cathode for a Li-ion battery, but its capacity fades over a charge/discharge cycle of Li1–x[Mn2]O4 (0 < x < 1) that is associated with a loss of Mn to the organic-liquid electrolyte. It is known that the disproportionation reaction 2Mn3+ = Mn2+ + Mn4+ occurs at the surface of a Mn spinel, and it is important to understand the atomic structure and composition of the surface of Revealing the Restructured Surface of Li[Mn2]O4 in order to understand how Mn loss occurs. We report a study of the surface reconstructionmore » of Revealing the Restructured Surface of Li[Mn2]O4 by aberration-corrected scanning transmission electron microscopy. The atomic structure coupled with Mn-valence and the distribution of the atomic ratio of oxygen obtained by electron energy loss spectroscopy reveals a thin, stable surface layer of Mn3O4, a subsurface region of Li1+x[Mn2]O4 with retention of bulk Li[Mn2]O4. We conclude that this observation is compatible with the disproportionation reaction coupled with oxygen deficiency and a displacement of surface Li+ from the Mn3O4 surface phase. These results provide a critical step toward understanding how Mn is lost from Li[Mn2]O4, once inside a battery.« less

  12. Synthesis, characterization and electrochemical performance of Al-substituted Li₂MnO₃

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Dhital, Chetan; Huq, Ashfia; Paranthaman, Mariappan Parans; Manivannan, Ayyakkannu; Torres-Castro, Loraine; Shojan, Jifi; Julien, Christian M.; Katiyar, Ram S.

    2015-08-08

    Li2MnO3 is known to be electrochemically inactive due to Mn in tetravalent oxidation state. Several compositions such as Li2MnO3 , Li1.5Al0.17MnO3, Li1.0Al0.33MnO3 and Li0.5Al0.5MnO3 were synthesized by a sol–gel Pechini method. All the samples were characterized with x-ray diffraction, Raman, x-ray photoelectron spectroscopy, scanning electron microscopy, Tap density and BET analyzer. X-ray diffraction patterns indicated the presence of monoclinic phase for pristine Li2MnO3and mixed monoclinic/spinel phases (Li2 - xMn1 - yAlx + yO3 + z) for Al-substituted Li2MnO3compounds. The Al substitution seems to occur both at Li and Mn sites, which could explain the presence of spinel phase. X-ray photoelectronmore » spectroscopy for Mn 2p orbital reveals a significant decrease in binding energy for Li1.0Al0.33MnO3 and Li0.5Al0.5MnO3 compounds. Cyclic voltammetry, charge/discharge cycles and electrochemical impedance spectroscopy were also performed. A discharge capacity of 24 mAh g-1 for Li2MnO3, 68 mAh g-1 for Li1.5Al0.17MnO3, 58 mAh g-1 for Li1.0Al0.33MnO3 and 74 mAh g-1 for Li0.5Al0.5MnO3 were obtained. As a result, aluminum substitutions increased the formation of spinel phase which is responsible for cycling.« less

  13. Resonant spin tunneling in randomly oriented nanospheres of Mn?? acetate

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Lendinez, S.; Billinge, S. J. L.; Zarzuela, R.; Tejada, J.; Terban, M. W.; Espin, J.; Imaz, I.; Maspoch, D.; Chudnovsky, E. M.

    2015-01-06

    We report measurements and theoretical analysis of resonant spin tunneling in randomly oriented nanospheres of a molecular magnet. Amorphous nanospheres of Mn?? acetate have been fabricated and characterized by chemical, infrared, TEM, X-ray, and magnetic methods. Magnetic measurements have revealed sharp tunneling peaks in the field derivative of the magnetization that occur at the typical resonant field values for the Mn?? acetate crystal in the field parallel to the easy axis.Theoretical analysis is provided that explains these observations. We argue that resonant spin tunneling in a molecular magnet can be established in a powder sample, without the need for amoresingle crystal and without aligning the easy magnetization axes of the molecules. This is confirmed by re-analyzing the old data on a powdered sample of non-oriented micron-size crystals of Mn?? acetate. Our findings can greatly simplify the selection of candidates for quantum spin tunneling among newly synthesized molecular magnets.less

  14. Stress induced anisotropy in CoFeMn soft magnetic nanocomposites...

    Office of Scientific and Technical Information (OSTI)

    Journal Article: Stress induced anisotropy in CoFeMn soft magnetic nanocomposites Citation Details In-Document Search Title: Stress induced anisotropy in CoFeMn soft magnetic ...

  15. Pulsed laser deposition of Mn doped CdSe quantum dots for improved solar cell performance

    SciTech Connect (OSTI)

    Dai, Qilin; Wang, Wenyong E-mail: jtang2@uwyo.edu; Tang, Jinke E-mail: jtang2@uwyo.edu; Sabio, Erwin M.

    2014-05-05

    In this work, we demonstrate (1) a facile method to prepare Mn doped CdSe quantum dots (QDs) on Zn{sub 2}SnO{sub 4} photoanodes by pulsed laser deposition and (2) improved device performance of quantum dot sensitized solar cells of the Mn doped QDs (CdSe:Mn) compared to the undoped QDs (CdSe). The band diagram of photoanode Zn{sub 2}SnO{sub 4} and sensitizer CdSe:Mn QD is proposed based on the incident-photon-to-electron conversion efficiency (IPCE) data. Mn-modified band structure leads to absorption at longer wavelengths than the undoped CdSe QDs, which is due to the exchange splitting of the CdSe:Mn conduction band by the Mn dopant. Three-fold increase in the IPCE efficiency has also been observed for the Mn doped samples.

  16. Pulsed laser deposition of Mn doped CdSe quantum dots for improved...

    Office of Scientific and Technical Information (OSTI)

    Pulsed laser deposition of Mn doped CdSe quantum dots for improved solar cell performance Citation Details In-Document Search Title: Pulsed laser deposition of Mn doped CdSe ...

  17. Coexistence of charge-density wave and ferromagnetism in Ni2MnGa...

    Office of Scientific and Technical Information (OSTI)

    Coexistence of charge-density wave and ferromagnetism in Ni2MnGa Citation Details In-Document Search Title: Coexistence of charge-density wave and ferromagnetism in Ni2MnGa ...

  18. Mixing antiferromagnets to tune NiFe-[IrMn/FeMn] interfacial spin-glasses, grains thermal stability, and related exchange bias properties

    SciTech Connect (OSTI)

    Akmaldinov, K.; Ducruet, C.; Portemont, C.; Joumard, I.; Prejbeanu, I. L.; Dieny, B.; Baltz, V.

    2014-05-07

    Spintronics devices and in particular thermally assisted magnetic random access memories require a wide range of ferromagnetic/antiferromagnetic (F/AF) exchange bias (EB) properties and subsequently of AF materials to fulfil diverse functionality requirements for the reference and storage. For the reference layer, large EB energies and high blocking temperature (T{sub B}) are required. In contrast, for the storage layer, mostly moderate T{sub B} are needed. One of the present issues is to find a storage layer with properties intermediate between those of IrMn and FeMn and in particular: (i) with a T{sub B} larger than FeMn for better stability at rest-T but lower than IrMn to reduce power consumption at write-T and (ii) with improved magnetic interfacial quality, i.e., with reduced interfacial glassy character for lower properties dispersions. To address this issue, the EB properties of F/AF based stacks were studied for various mixed [IrMn/FeMn] AFs. In addition to EB loop shifts, the F/AF magnetic interfacial qualities and the AF grains thermal stability are probed via measurements of the low- and high-temperature contributions to the T{sub B} distributions, respectively. A tuning of the above three parameters is observed when evolving from IrMn to FeMn via [IrMn/FeMn] repetitions.

  19. Epitaxial Growth of Intermetallic MnPt Films on Oxides and Large Exchange Bias

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Liu, Zhiqi; Biegalski, Michael D.; Hsu, Shang-Lin; Shang, Shunli; Marker, Cassie; Liu, Jian; Li, Li; Fan, Lisha S.; Meyer, Tricia L.; Wong, Anthony T.; et al

    2015-11-05

    High-quality epitaxial growth of intermetallic MnPt films on oxides is achieved, with potential for multiferroic heterostructure applications. Antisite-stabilized spin-flipping induces ferromagnetism in MnPt films, although it is robustly antiferromagnetic in bulk. Moreover, highly ordered antiferromagnetic MnPt films exhibit superiorly large exchange coupling with a ferromagnetic layer.

  20. Epitaxial growth of intermetallic MnPt films on oxides and large exchange bias

    SciTech Connect (OSTI)

    Liu, Zhiqi; Biegalski, Michael D.; Hsu, Shang-Lin; Shang, Shunli; Marker, Cassie; Liu, Jian; Li, Li; Fan, Lisha S.; Meyer, Tricia L.; Wong, Anthony T.; Nichols, John A.; Chen, Deyang; You, Long; Chen, Zuhuang; Wang, Kai; Wang, Kevin; Ward, Thomas Z.; Gai, Zheng; Lee, Ho Nyung; Sefat, Athena S.; Lauter, Valeria; Liu, Zi-kui; Christen, Hans M.

    2015-11-05

    High-quality epitaxial growth of intermetallic MnPt films on oxides is achieved, with potential for multiferroic heterostructure applications. Antisite-stabilized spin-flipping induces ferromagnetism in MnPt films, although it is robustly antiferromagnetic in bulk. Thus, highly ordered antiferromagnetic MnPt films exhibit superiorly large exchange coupling with a ferromagnetic layer.

  1. Cationic disorder and Mn{sup 3+}/Mn{sup 4+} charge ordering in the B? and B? sites of Ca{sub 3}Mn{sub 2}NbO{sub 9} perovskite: a comparison with Ca{sub 3}Mn{sub 2}WO{sub 9}

    SciTech Connect (OSTI)

    Lpez, C.A.; Saleta, M.E.; Pedregosa, J.C.; Snchez, R.D.; Alonso, J.A.; and others

    2014-02-15

    We describe the preparation, crystal structure determination, magnetic and transport properties of two novel Mn-containing perovskites, with a different electronic configuration for Mn atoms located in B site. Ca{sub 3}Mn{sup 3+}{sub 2}WO{sub 9} and Ca{sub 3}Mn{sup 3+/4+}{sub 2}NbO{sub 9} were synthesized by standard ceramic procedures; the crystallographic structure was studied from X-ray powder diffraction (XRPD) and neutron powder diffraction (NPD). Both phases exhibit a monoclinic symmetry (S.G.: P2{sub 1}/n); Ca{sub 3}Mn{sub 2}WO{sub 9} presents a long-range ordering over the B sites, whereas Ca{sub 3}Mn{sub 2}NbO{sub 9} is strongly disordered. By in-situ NPD, the temperature evolution of the structure study presents an interesting evolution in the octahedral size (?MnO?) for Ca{sub 3}Mn{sub 2}NbO{sub 9}, driven by a charge ordering effect between Mn{sup 3+} and Mn{sup 4+} atoms, related to the anomaly observed in the transport measurements at T?160 K. Both materials present a magnetic order below T{sub C}=30 K and 40 K for W and Nb materials, respectively. The magneto-transport measurements display non-negligible magnetoresistance properties in the paramagnetic regime. - Graphical abstract: Comparison between the octahedron size and the magnetic behaviour for Ca{sub 3}Mn{sub 2}NbO{sub 9} in the temperature region where the charge and magnetic order occur. Display Omitted - Highlights: Two novel Mn-containing double perovskites were obtained by solid-state reactions. Both double perovskites are monoclinic (P2{sub 1}/n) determined by XRPD and NPD. Ca{sub 3}Mn{sub 2}WO{sub 9} contains Mn{sup 3+} while Ca{sub 3}Mn{sub 2}NbO{sub 9} includes mixed-valence cations Mn{sup 3+}/Mn{sup 4+}. Ca{sub 3}Mn{sub 2}NbO{sub 9} presents a charge-ordering effect between Mn{sup 3+} and Mn{sup 4+} evidenced by NPD. The magnetic and transport studies evidenced the charge ordering in Ca{sub 3}Mn{sub 2}NbO{sub 9}.

  2. Neutron scattering study of spin ordering and stripe pinning in superconducting La<mn>1.93mn>Sr>0.07mn>CuO>4mn>

    SciTech Connect (OSTI)

    Jacobsen, H.; Zaliznyak, I. A.; Savici, A. T.; Winn, B. L.; Chang, S.; Hücker, M.; Gu, G. D.; Tranquada, J. M.

    2015-11-20

    The relationships among charge order, spin fluctuations, and superconductivity in underdoped cuprates remain controversial. We use neutron scattering techniques to study these phenomena in La<mn>1.93mn>Sr>0.07mn>CuO>4mn> a superconductor with a transition temperature of Tc = 20 K. At T<< Tc, we find incommensurate spin fluctuations with a quasielastic energy spectrum and no sign of a gap within the energy range from 0.2 to 15 meV. A weak elastic magnetic component grows below ~ 10 K, consistent with results from local probes. Regarding the atomic lattice, we have discovered unexpectedly strong fluctuations of the CuO6 octahedra about Cu-O bonds, which are associated with inequivalent O sites within the CuO2 planes. Moreover, we observed a weak elastic (3 30) superlattice peak that implies a reduced lattice symmetry. The presence of inequivalent O sites rationalizes various pieces of evidence for charge stripe order in underdoped La2-xSrxCuO4. The coexistence of superconductivity with quasi-static spin-stripe order suggests the presence of intertwined orders; however, the rotation of the stripe orientation away from the Cu-O bonds might be connected with evidence for a finite gap at the nodal points of the superconducting gap function.

  3. Clarification of enhanced ferromagnetism in Be-codoped InMnP fabricated using Mn/InP:Be bilayers grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Shon, Yoon; Lee, Sejoon; Taek Yoon, Im; Jeon, H. C.; Lee, D. J.; Kang, T. W.; Song, J. D.; Yoon, Chong S.; Kim, D. Y.; Park, C. S.

    2011-11-07

    The p-type InMnP:Be epilayers were prepared by the sequential growth of Mn/InP:Be bilayers using molecular-beam-epitaxy and the subsequent in-situ annealing at 200-300 deg. C. In triple-axis x-ray diffraction patterns, the samples revealed a shoulder peak indicative of intrinsic InMnP. The ferromagnetic transition in InMnP:Be was observed to occur at the elevated temperature of {approx}140 K, and the ferromagnetic spin-domains clearly appeared in magnetic force microscopy images. The improved ferromagnetic properties are attributed to the increased p-d hybridation due to high p-type conductivity of InMnP:Be (p {approx} 10{sup 20 }cm{sup -3}). The results suggest that enhanced ferromagnetism can be effectively obtained from Be-codoped InMnP.

  4. Magnetic properties of α−MnO{sub 2} and Co-doped α−MnO{sub 2} nanowires

    SciTech Connect (OSTI)

    Stella, C. Soundararajan, N. Ramachandran, K.

    2014-04-24

    α−MnO{sub 2} and Co-doped α−MnO{sub 2} nanowires (NWs) were synthesized by hydrothermal method. The structural characterization by XRD revealed the tetragonal structure of α−MnO{sub 2}. The formation of one dimensional (1D) NWs of pure and Co-doped α−MnO{sub 2} was confirmed from SEM. From UV-Vis absorption spectra, it is found that both pure and Co-doped α−MnO{sub 2} NWs showed blue shift compared to bulk, which revealed the quantum confinement in the synthesized samples. The magnetic properties were analyzed by VSM, which suggest that pure and doped α−MnO{sub 2} exhibit ferromagnetic behavior at room temperature (RT)

  5. Role of t{sub 2g} electrons in Mn-Tb coupling of multiferroic TbMnO{sub 3}

    SciTech Connect (OSTI)

    Guo, Y. Y.; Wang, Y. L.; Liu, J.-M.; Wei, T.

    2014-08-14

    We investigate the effect of Cr-doping in polycrystalline TbMn{sub 1?x}Cr{sub x}O{sub 3} (x???6%) ceramics on the magnetism, ferroelectricity, and dielectricity. The Cr substitution gradually suppresses the ferroelectricity induced by the Mn spiral spin ordering, and results in a stronger modulation of polarization by magnetic field with increasing x. However, the transition temperature T{sub Tb} corresponding to onset of Tb magnetic ordering has barely shifted with Cr doping. In other words, although the Cr-doping obviously disrupts the Mn spiral spin ordering, the exchange field J{sub Mn-Tb} acting on the Tb moments from the Mn-spin structure is hardly impacted. Our work demonstrates that the e{sub g} electron of Mn{sup 3+} plays an important role in forming the Mn spiral spin order, but the f-d exchange interaction between the Mn 3d spins and the Tb 4f moments in multiferroic TbMnO{sub 3} almost involves only the t{sub 2g} electrons.

  6. Effect of Mn substitution on the transport properties of co-sputtered Fe{sub 3−x}Mn{sub x}Si epilayers

    SciTech Connect (OSTI)

    Tang, M.; Jin, C.; Bai, H. L.

    2014-11-07

    Motivated by the theoretical calculations that Fe{sub 3−x}Mn{sub x}Si can simultaneously exhibit a high spin polarization with a high Curie temperature to be applied in spintronic devices, and in order to further study the effect of Mn contents on the physical properties of Fe{sub 3−x}Mn{sub x}Si, we have investigated the effect of Mn substitution on the transport properties of epitaxial Fe{sub 3−x}Mn{sub x}Si (0≤x≤1) films systematically. The Fe{sub 3−x}Mn{sub x}Si films were epitaxially grown on MgO(001) plane with 45° rotation. The magnetization for various x shows enhanced irreversibility, implying the antiferromagnetic ordering induced by the substitution of Mn. A metal-semiconductor crossover was observed due to the enhanced disorders of interactions and the local lowering of symmetry induced by the substitution of Mn. The single-domain state in the Fe{sub 3−x}Mn{sub x}Si films leads to twofold symmetric curves of the anisotropic magnetoresistance and planar Hall resistivity.

  7. Plutonium Oxidation and Subsequent Reduction by Mn (IV) Minerals

    SciTech Connect (OSTI)

    KAPLAN, DANIEL

    2005-09-13

    Plutonium sorbed to rock tuff was preferentially associated with manganese oxides. On tuff and synthetic pyrolusite (Mn{sup IV}O{sub 2}), Pu(IV) or Pu(V) was initially oxidized, but over time Pu(IV) became the predominant oxidation state of sorbed Pu. Reduction of Pu(V/VI), even on non-oxidizing surfaces, is proposed to result from a lower Gibbs free energy of the hydrolyzed Pu(IV) surface species versus that of the Pu(V) or Pu(VI) surface species. This work suggests that despite initial oxidation of sorbed Pu by oxidizing surfaces to more soluble forms, the less mobile form of Pu, Pu(IV), will dominate Pu solid phase speciation during long term geologic storage. The safe design of a radioactive waste or spent nuclear fuel geologic repository requires a risk assessment of radionuclides that may potentially be released into the surrounding environment. Geochemical knowledge of the radionuclide and the surrounding environment is required for predicting subsurface fate and transport. Although difficult even in simple systems, this task grows increasingly complicated for constituents, like Pu, that exhibit complex environmental chemistries. The environmental behavior of Pu can be influenced by complexation, precipitation, adsorption, colloid formation, and oxidation/reduction (redox) reactions (1-3). To predict the environmental mobility of Pu, the most important of these factors is Pu oxidation state. This is because Pu(IV) is generally 2 to 3 orders of magnitude less mobile than Pu(V) in most environments (4). Further complicating matters, Pu commonly exists simultaneously in several oxidation states (5, 6). Choppin (7) reported Pu may exist as Pu(IV), Pu(V), or Pu(VI) oxic natural groundwaters. It is generally accepted that plutonium associated with suspended particulate matter is predominantly Pu(IV) (8-10), whereas Pu in the aqueous phase is predominantly Pu(V) (2, 11-13). The influence of the character of Mn-containing minerals expected to be found in subsurface

  8. Relation between the magnetization and the electrical properties of alloy GaSb-MnSb films

    SciTech Connect (OSTI)

    Koplak, O. V.; Polyakov, A. A.; Davydov, A. B.; Morgunov, R. B.; Talantsev, A. D.; Kochura, A. V.; Fedorchenko, I. V.; Novodvorskii, O. A.; Parshina, L. S.; Khramova, O. D.; Shorokhova, A. V.; Aronzon, B. A.

    2015-06-15

    The influence of the charge carrier concentration on the magnetic properties of GaSb-MnSb alloys is studied. The ferromagnetism of GaSb-MnSb films is caused by the presence of MnSb granules and manifests itself in both magnetometric measurements and the presence of an anisotropic magnetoresistance and the anomalous Hall effect. Electric conduction is executed by charge carriers (holes) in a GaSb matrix. The magnetization of clusters depends on stoichiometry and the concentration of Mn{sup 2+} and Mn{sup 3+} ions, which is specified by the film growth conditions. At high film growth temperatures, ferromagnetic clusters containing Mn{sup 2+} ions mainly form. At low growth temperatures, an antiferromagnetic phase containing Mn{sup 3+} ions forms.

  9. Effect of Composition and Heat Treatment on MnBi Magnetic Materials

    SciTech Connect (OSTI)

    Cui, Jun; Choi, Jung-Pyung; Polikarpov, Evgueni; Bowden, Mark E.; Xie, Wei; Li, Guosheng; Nie, Zimin; Zarkevich, Nikolai; Kramer, Matthew J.; Johnson, Duane D.

    2014-08-17

    The metallic compound MnBi is a promising rare-earth-free permanent magnet material. Compare to other rare-earth-free candidates, MnBi stands out for its high intrinsic coercivity (Hci) and its large positive temperature coefficient. Several groups have demonstrated that the Hci of MnBi compound in thin film or in powder form can exceed 12 kOe and 26 kOe at 300 K and 523 K, respectively. Such steep increase in Hci with increasing temperature is unique to MnBi. Consequently, MnBi is a highly sought-after hard phase for exchange coupling nanocomposite magnets. The reaction between Mn and Bi is peritectic, so Mn tends to precipitate out of the MnBi liquid during the solidification process. As result, the composition of the Mn-Bi alloy with the largest amount of the desired LTP (low temperature phase) MnBi and highest saturation magnetization will be over-stoichiometric and rich in Mn. The amount of additional Mn required to compensate the Mn precipitation depends on solidification rate: the faster the quench speed, the less Mn precipitates. Here we report a systematic study of the effect of composition and heat treatments on the phase contents and magnetic properties of Mn-Bi alloys. In this study, Mn-Bi alloys with 14 compositions were prepared using conventional metallurgical methods such as arc melting and vacuum heat treatment, and the obtained alloys were analyzed for compositions, crystal structures, phase content, and magnetic properties. The results show that the composition with 55 at.% Mn exhibits the highest LTP MnBi content and the highest magnetization. The sample with this composition shows >90 wt.% LTP MnBi content. Its measured saturation magnetization is 68 emu/g with 2.3 T applied field at 300 K; its coercivity is 13 kOe and its energy product is 12 MGOe at 300 K. A bulk magnet fabricated using this powder exhibits an energy product of 8.2 MGOe.

  10. Magnetostructural phase transformations in Tb 1-x Mn 2

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zou, Junding; Paudyal, Durga; Liu, Jing; Mudryk, Yaroslav; Pecharsky, Vitalij K.; Gschneidner, Karl A.

    2015-01-16

    Magnetism and phase transformations in non-stoichiometric Tb1-xMn2 (x = 0.056, 0.039) have been studied as functions of temperature and magnetic field using magnetization, heat capacity, and X-ray powder diffraction measurements. Lowering the temperature, the compounds sequentially order ferrimagnetically and antiferromagnetically, and finally, exhibit spin reorientation transitions. Moreover, these structural distortions from room temperature cubic to low temperature rhombohedral structures occur at TN, and are accompanied by large volume changes reaching ~-1.27% and -1.42%, respectively. First principles electronic structure calculations confirm the phase transformation from the ferrimagnetic cubic structure to the antiferromagnetic rhombohedral structure in TbMn2.

  11. On the state of Mn impurity implanted in Si

    SciTech Connect (OSTI)

    Orlov, A. F.; Bublik, V. T.; Vdovin, V. I.; Agafonov, Yu. A.; Balagurov, L. A.; Zinenko, V. I.; Kulemanov, I. V.; Shcherbachev, K. D.

    2009-07-15

    The state of manganese impurity in implanted silicon at implantation doses of up to 5 x 10{sup 16} cm{sup -2} has been investigated by X-ray diffraction and transmission electron microscopy. It is established that, after short-term vacuum annealing at 850{sup o}C, most of the implanted manganese impurities are in microinclusions up to 20 nm in size formed by a tetragonal silicide phase of the Mn{sub 15}Si{sub 26} type.

  12. High-pressure structural study of MnF2

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Stavrou, Elissaios; Yao, Yansun; Goncharov, Alexander F.; Konopkova, Zuzana; Raptis, Constantine

    2015-02-01

    In this study, manganese fluoride (MnF2) with the tetragonal rutile-type structure has been studied using a synchrotron angle-dispersive powder x-ray diffraction and Raman spectroscopy in a diamond anvil cell up to 60 GPa at room temperature combined with first-principles density functional calculations. The experimental data reveal two pressure-induced structural phase transitions with the following sequence: rutile → SrI2 type (3 GPa)→ α–PbCl2 type (13 GPa). Complete structural information, including interatomic distances, has been determined in the case of MnF2 including the exact structure of the debated first high-pressure phase. First-principles density functional calculations confirm this phase transition sequence, and themore » two calculated transition pressures are in excellent agreement with the experiment. Lattice dynamics calculations also reproduce the experimental Raman spectra measured for the ambient and high-pressure phases. The results are discussed in line with the possible practical use of rutile-type fluorides in general and specifically MnF2 as a model compound to reveal the HP structural behavior of rutile-type SiO2 (Stishovite).« less

  13. Manganese valence and coordination structure in Mn,Mg-codoped {gamma}-AlON green phosphor

    SciTech Connect (OSTI)

    Takeda, Takashi; Xie, Rong-Jun; Hirosaki, Naoto; Matsushita, Yoshitaka; Honma, Tetuso

    2012-10-15

    The valence and coordination structure of manganese in a Mn,Mg-codoped {gamma}-AlON spinel-type oxynitride green phosphor were studied by synchrotron X-ray diffraction and absorption fine structure measurements. The absorption edge position of the XANES revealed the bivalency of Mn. Two cation sites are available in the spinel structure for cation doping: a tetrahedral site and an octahedral site. The pre-edge of the XANES and the distance to the nearest neighbor atoms obtained from the EXAFS measurement showed that Mn was situated at the tetrahedral site. Rietveld analysis showed that the vacancy occupied the octahedral site. The preferential occupation of the tetrahedral site by Mn and the roles of N and Mg are discussed in relation to the spinel crystal structure. - Graphical Abstract: Fourier transform of EXAFS of Mn K-edge for Mn,Mg-codoped green phosphor and Mn coordination structure. Highlights: Black-Right-Pointing-Pointer Mn, Mg-codoped {gamma}-AlON green phosphor for white LED. Black-Right-Pointing-Pointer The valence of Mn is divalent. Black-Right-Pointing-Pointer Mn occupies the tetrahedral site in the spinel structure.

  14. Ferromagnetic interactions and martensitic transformation in Fe doped Ni-Mn-In shape memory alloys

    SciTech Connect (OSTI)

    Lobo, D. N.; Priolkar, K. R.; Emura, S.; Nigam, A. K.

    2014-11-14

    The structure, magnetic, and martensitic properties of Fe doped Ni-Mn-In magnetic shape memory alloys have been studied by differential scanning calorimetry, magnetization, resistivity, X-ray diffraction (XRD), and EXAFS. While Ni{sub 2}MnIn{sub 1?x}Fe{sub x} (0???x???0.6) alloys are ferromagnetic and non martensitic, the martensitic transformation temperature in Ni{sub 2}Mn{sub 1.5}In{sub 1?y}Fe{sub y} and Ni{sub 2}Mn{sub 1.6}In{sub 1?y}Fe{sub y} increases for lower Fe concentrations (y???0.05) before decreasing sharply for higher Fe concentrations. XRD analysis reveals presence of cubic and tetragonal structural phases in Ni{sub 2}MnIn{sub 1?x}Fe{sub x} at room temperature with tetragonal phase content increasing with Fe doping. Even though the local structure around Mn and Ni in these Fe doped alloys is similar to martensitic Mn rich Ni-Mn-In alloys, presence of ferromagnetic interactions and structural disorder induced by Fe affect Mn-Ni-Mn antiferromagnetic interactions resulting in suppression of martensitic transformation in these Fe doped alloys.

  15. Effect of composition and heat treatment on MnBi magnetic materials

    SciTech Connect (OSTI)

    Cui, Jun [Pacific Northwest National Laboratory; Choi, Jung-Pyung [Pacific Northwest National Laboratory; Polikarpov, Evgueni [Pacific Northwest National Laboratory; Bowden, Mark E [Pacific Northwest National Laboratory; Xie, Wei [Pacific Northwest National Laboratory; Li, Guosheng [Pacific Northwest National Laboratory; Nie, Zimin [Pacific Northwest National Laboratory; Zarkevich, Nikolai [Ames Laboratory; Kramer, Matthew J [Ames Laboratory; Johnson, Duane [Ames Laboratory

    2014-10-01

    The metallic compound MnBi is a promising rare-earth-free permanent magnet material, unique among all candidates for its high intrinsic coercivity (Hci) and its large positive temperature coefficient. The Hci of MnBi in thin-film or powder form can exceed 12 and 26 kOe at 300 and 523 K, respectively. Such a steep rise in Hci with increasing temperature is unique to MnBi. Consequently, MnBi is a highly sought-after hard phase for exchange coupling nanocomposite magnets. However, the reaction between Mn and Bi is peritectic, and hence Mn tends to precipitate out of the MnBi liquid during the solidification process. As result, when the alloy is prepared using conventional induction or arc-melting casting methods, additional Mn is required to compensate the precipitation of Mn. In addition to composition, post-casting annealing plays an important role in obtaining a high content of MnBi low-temperature phase (LTP) because the annealing encourages the Mn precipitates and the unreacted Bi to react, forming the desired LTP phase. Here we report a systematic study of the effect of composition and heat treatments on the phase content and magnetic properties of MnBi alloys. In this study, 14 compositions were prepared using conventional metallurgical methods, and the compositions, crystal structures, phase content and magnetic properties of the resulting alloys were analyzed. The results show that the composition with 55 at.% Mn exhibits both the highest LTP content (93 wt.%) and magnetization (74 emu g?1 with 9 T applied field at 300 K).

  16. Dynamic study of (De)sodiation in alpha-MnO2 nanowires

    SciTech Connect (OSTI)

    Yuan, Yifei; Ma, Lu; He, Kun; Yao, Wentao; Nie, Anmin; Bi, Xuanxuan; Amine, Khalil; Wu, Tianpin; Lu, Jun; Shahbazian-Yassr, Reza

    2016-01-01

    In this report, the electrochemical sodiation and desodiation in single crystalline alpha-MnO2 nanowires are studied dynamically at both single particle level using in situ transmission electron microscopy (TEM) and bulk level using in situ synchrotron X-ray. The TEM results suggest that the first sodiation process starts with tunnel-based Na+ intercalation, experiences the formation of Na0.5MnO2 as a result of tunnel degradation, and ends with the Mn2O3 phase. The inserted Na+ can be partially extracted out of the sodiated products, and the following cycles are dominated by the reversible conversion reaction between Na0.5MnO2 and Mn2O3. The Mn valence evolution inside a cycling coin using alpha-MnO2 nanowire electrode also exhibits partially reversible characteristic, agreeing well with the in situ TEM analysis. The sodiation is compared with lithiation in the same alpha-MnO2 nanowires. Both Na+ and Li+ interact with the tunneled structure via a similar tunnel -driven intercalation mechanism before Mn4+ is reduced to Mn3.5+. For the following deep insertion, the tunnels survive up. to LiMnO2 (Mn3+) during lithiation, while the sodiation proceeds via a different mechanism that involves obvious phase transition and fast tunnel degradation after Mn's valence is below 3.5+. The difference in charge carrier insertion mechanisms can be ascribed to the strong interaction between the tunnel frame and inserted Na+ possessing a larger ionic size than inserted Li+.

  17. Large exchange bias enhancement in (Pt(or Pd)/Co)/IrMn/Co trilayers with ultrathin IrMn thanks to interfacial Cu dusting

    SciTech Connect (OSTI)

    Vinai, G. [SPINTEC, UMR 8191 CEA/CNRS/UJF/Grenoble-INP, CEA/INAC, 17, rue des Martyrs, 38054 Grenoble (France); Crocus Technology, 4 Place Robert Schuman, 38054 Grenoble (France); Moritz, J. [Institut Jean Lamour, UMR 7198 CNRS - Universit de Lorraine, Bd des Aiguillettes, BP 70239, F-54506 Vandoeuvre-les-Nancy Cedex (France); Bandiera, S. [Crocus Technology, 4 Place Robert Schuman, 38054 Grenoble (France); Prejbeanu, I. L.; Dieny, B. [SPINTEC, UMR 8191 CEA/CNRS/UJF/Grenoble-INP, CEA/INAC, 17, rue des Martyrs, 38054 Grenoble (France)

    2014-04-21

    The magnitude of exchange bias (H{sub ex}) at room temperature can be significantly enhanced in IrMn/Co and (Pt(or Pd)/Co)/IrMn/Co structures thanks to the insertion of an ultrathin Cu dusting layer at the IrMn/Co interface. The combination of trilayer structure and interfacial Cu dusting leads to a three-fold increase in H{sub ex} as compared to the conventional IrMn/Co bilayer structure, with an increased blocking temperature (T{sub B}) and a concave curvature of the temperature dependence H{sub ex}(T), ideal for improved Thermally Assisted-Magnetic Random Access Memory storage layer. This exchange bias enhancement is ascribed to a reduction of the spin frustration at the IrMn/Co interface thanks to interfacial Cu addition.

  18. Synthesis, characterization and electrochemical performance of Al-substituted Li₂MnO₃

    SciTech Connect (OSTI)

    Dhital, Chetan; Huq, Ashfia; Paranthaman, Mariappan Parans; Manivannan, Ayyakkannu; Torres-Castro, Loraine; Shojan, Jifi; Julien, Christian M.; Katiyar, Ram S.

    2015-08-08

    Li2MnO3 is known to be electrochemically inactive due to Mn in tetravalent oxidation state. Several compositions such as Li2MnO3 , Li1.5Al0.17MnO3, Li1.0Al0.33MnO3 and Li0.5Al0.5MnO3 were synthesized by a sol–gel Pechini method. All the samples were characterized with x-ray diffraction, Raman, x-ray photoelectron spectroscopy, scanning electron microscopy, Tap density and BET analyzer. X-ray diffraction patterns indicated the presence of monoclinic phase for pristine Li2MnO3and mixed monoclinic/spinel phases (Li2 - xMn1 - yAlx + yO3 + z) for Al-substituted Li2MnO3compounds. The Al substitution seems to occur both at Li and Mn sites, which could explain the presence of spinel phase. X-ray photoelectron spectroscopy for Mn 2p orbital reveals a significant decrease in binding energy for Li1.0Al0.33MnO3 and Li0.5Al0.5MnO3 compounds. Cyclic voltammetry, charge/discharge cycles and electrochemical impedance spectroscopy were also performed. A discharge capacity of 24 mAh g-1 for Li2MnO3, 68 mAh g-1 for Li1.5Al0.17MnO3, 58 mAh g-1 for Li1.0Al0.33MnO3 and 74 mAh g-1 for Li0.5Al0.5MnO3 were obtained. As a result, aluminum substitutions increased the formation of spinel phase which is responsible for cycling.

  19. The magnetic origin of multiferroic Y{sub 2}CoMnO{sub 6}

    SciTech Connect (OSTI)

    Jia, Ting; Zeng, Zhi; Li, X. G.; Lin, H. Q.

    2015-05-07

    It has been found experimentally that the ferroelectricity in Y{sub 2}CoMnO{sub 6} is driven by a magnetic ordering of collinear up-up-down-down (↑↑↓↓). Here, the origin of the magnetism and thereby ferroelectricity is studied using first-principles calculations. We first confirm that the experimentally observed ↑↑↓↓ antiferromagnetic structure is the ground state of Y{sub 2}CoMnO{sub 6}. Additionally, both the Co{sup 2+} and Mn{sup 4+} are in the high-spin state. By analyzing the exchange coupling and corresponding pathways, we conclude that the ↑↑↓↓ spin order in Y{sub 2}CoMnO{sub 6} originates from a subtle competition between the ferromagnetic Co-O-Mn super-exchange and antiferromagnetic Co-Mn direct-exchange along c axis.

  20. Structural and ferromagnetic properties of an orthorhombic phase of MnBi stabilized with Rh additions

    SciTech Connect (OSTI)

    Taufour, Valentin; Thimmaiah, Srinivasa; March, Stephen; Saunders, Scott; Sun, Kewei; Lamichhane, Tej Nath; Kramer, Matthew J.; Bud’ko, Sergey L.; Canfield, Paul C.

    2015-07-28

    The article addresses the possibility of alloy elements in MnBi which may modify the thermodynamic stability of the NiAs-type structure without significantly degrading the magnetic properties. The addition of small amounts of Rh and Mn provides an improvement in the thermal stability with some degradation of the magnetic properties. The small amounts of Rh and Mn additions in MnBi stabilize an orthorhombic phase whose structural and magnetic properties are closely related to the ones of the previously reported high-temperature phase of MnBi (HT MnBi). The properties of the HT MnBi, which is stable between 613 and 719 K, have not been studied in detail because of its transformation to the stable low-temperature MnBi (LT MnBi), making measurements near and below its Curie temperature difficult. The Rh-stabilized MnBi with chemical formula Mn1.0625–xRhxBi [x=0.02(1)] adopts a new superstructure of the NiAs/Ni2In structure family. It is ferromagnetic below a Curie temperature of 416 K. The critical exponents of the ferromagnetic transition are not of the mean-field type but are closer to those associated with the Ising model in three dimensions. The magnetic anisotropy is uniaxial; the anisotropy energy is rather large, and it does not increase when raising the temperature, contrary to what happens in LT MnBi. The saturation magnetization is approximately 3μB/f.u. at low temperatures. Thus, while this exact composition may not be application ready, it does show that alloying is a viable route to modifying the stability of this class of rare-earth-free magnet alloys.

  1. Cr(OH)₃(s) Oxidation Induced by Surface Catalyzed Mn(II) Oxidation

    SciTech Connect (OSTI)

    Namgung, Seonyi; Kwon, M.; Qafoku, Nikolla; Lee, Gie Hyeon

    2014-09-16

    This study examined the feasibility of Cr(OH)₃(s) oxidation mediated by surface catalyzed Mn(II) oxidation under common groundwater pH conditions as a potential pathway of natural Cr(VI) contaminations. Dissolved Mn(II) (50 μM) was reacted with or without synthesized Cr(OH)₃(s) (1.0 g/L) at pH 7 – 9 under oxic or anoxic conditions. In the absence of Cr(OH)₃(s), homogeneous Mn(II) oxidation by dissolved O₂ was not observed at pH ≤ 8.0 for 50 d. At pH 9.0, by contrast, dissolved Mn(II) was completely removed within 8 d and precipitated as hausmannite. When Cr(OH)₃(s) was present, this solid was oxidized and released substantial amounts of Cr(VI) as dissolved Mn(II) was added into the suspension at pH ≥ 8.0 under oxic conditions. Our results suggest that Cr(OH)₃(s) was readily oxidized by a newly formed Mn oxide as a result of Mn(II) oxidation catalyzed on Cr(OH)₃(s) surface. XANES analysis of the residual solids after the reaction between 1.0 g/L Cr(OH)₃(s) and 204 μM Mn(II) at pH 9.0 for 22 d revealed that the product of surface catalyzed Mn(II) oxidation resembled birnessite. The rate and extent of Cr(OH)₃(s) oxidation was likely controlled by those of surface catalyzed Mn(II) oxidation as the production of Cr(VI) increased with increasing pH and initial Mn(II) concentrations. This study evokes the potential environmental hazard of sparingly soluble Cr(OH)₃(s) that can be a source of Cr(VI) in the presence of dissolved Mn(II).

  2. Structural and ferromagnetic properties of an orthorhombic phase of MnBi stabilized with Rh additions

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Taufour, Valentin; Thimmaiah, Srinivasa; March, Stephen; Saunders, Scott; Sun, Kewei; Lamichhane, Tej Nath; Kramer, Matthew J.; Bud’ko, Sergey L.; Canfield, Paul C.

    2015-07-28

    The article addresses the possibility of alloy elements in MnBi which may modify the thermodynamic stability of the NiAs-type structure without significantly degrading the magnetic properties. The addition of small amounts of Rh and Mn provides an improvement in the thermal stability with some degradation of the magnetic properties. The small amounts of Rh and Mn additions in MnBi stabilize an orthorhombic phase whose structural and magnetic properties are closely related to the ones of the previously reported high-temperature phase of MnBi (HT MnBi). The properties of the HT MnBi, which is stable between 613 and 719 K, have notmore » been studied in detail because of its transformation to the stable low-temperature MnBi (LT MnBi), making measurements near and below its Curie temperature difficult. The Rh-stabilized MnBi with chemical formula Mn1.0625–xRhxBi [x=0.02(1)] adopts a new superstructure of the NiAs/Ni2In structure family. It is ferromagnetic below a Curie temperature of 416 K. The critical exponents of the ferromagnetic transition are not of the mean-field type but are closer to those associated with the Ising model in three dimensions. The magnetic anisotropy is uniaxial; the anisotropy energy is rather large, and it does not increase when raising the temperature, contrary to what happens in LT MnBi. The saturation magnetization is approximately 3μB/f.u. at low temperatures. Thus, while this exact composition may not be application ready, it does show that alloying is a viable route to modifying the stability of this class of rare-earth-free magnet alloys.« less

  3. Electronic Structure and Oxidation State Changes in the Mn (4) Ca Cluster of Photosystem II

    SciTech Connect (OSTI)

    Yano, J.; Pushkar, Y.; Messinger, J.; Bergmann, U.; Glatzel, P.; Yachandra, V.K.; /SLAC

    2012-08-17

    Oxygen-evolving complex (Mn{sub 4}Ca cluster) of Photosystem II cycles through five intermediate states (S{sub i}-states, i = 0-4) before a molecule of dioxygen is released. During the S-state transitions, electrons are extracted from the OEC, either from Mn or alternatively from a Mn ligand. The oxidation state of Mn is widely accepted as Mn{sub 4}(III{sub 2},IV{sub 2}) and Mn{sub 4}(III,IV{sub 3}) for S{sub 1} and S{sub 2} states, while it is still controversial for the S{sub 0} and S{sub 3} states. We used resonant inelastic X-ray scattering (RIXS) to study the electronic structure of Mn{sub 4}Ca complex in the OEC. The RIXS data yield two-dimensional plots that provide a significant advantage by obtaining both K-edge pre-edge and L-edge-like spectra (metal spin state) simultaneously. We have collected data from PSII samples in the each of the S-states and compared them with data from various inorganic Mn complexes. The spectral changes in the Mn 1s2p{sub 3/2} RIXS spectra between the S-states were compared to those of the oxides of Mn and coordination complexes. The results indicate strong covalency for the electronic configuration in the OEC, and we conclude that the electron is transferred from a strongly delocalized orbital, compared to those in Mn oxides or coordination complexes. The magnitude for the S{sub 0} to S{sub 1}, and S{sub 1} to S{sub 2} transitions is twice as large as that during the S{sub 2} to S{sub 3} transition, indicating that the electron for this transition is extracted from a highly delocalized orbital with little change in charge density at the Mn atoms.

  4. Preparation and electrochemical properties of lamellar MnO{sub 2} for supercapacitors

    SciTech Connect (OSTI)

    Yan, Jun; Wei, Tong; Cheng, Jie; Fan, Zhuangjun; Zhang, Milin

    2010-02-15

    Lamellar birnessite-type MnO{sub 2} materials were prepared by changing the pH of the initial reaction system via hydrothermal synthesis. The interlayer spacing of MnO{sub 2} with a layered structure increased gradually when the initial pH value varied from 12.43 to 2.81, while the MnO{sub 2}, composed of {alpha}-MnO{sub 2} and {gamma}-MnO{sub 2}, had a rod-like structure at pH 0.63. Electrochemical studies indicated that the specific capacitance of birnessite-type MnO{sub 2} was much higher than that of rod-like MnO{sub 2} at high discharge current densities due to the lamellar structure with fast intercalation/deintercalation of protons and high utilization of MnO{sub 2}. The initial specific capacitance of MnO{sub 2} prepared at pH 2.81 was 242.1 F g{sup -1} at 2 mA cm{sup -2} in 2 mol L{sup -1} (NH{sub 4}){sub 2}SO{sub 4} aqueous electrolyte. The capacitance increased by about 8.1% of initial capacitance after 200 cycles at a current density of 100 mA cm{sup -2}.

  5. In operando X-ray studies of the conversion reaction in Mn3O4...

    Office of Scientific and Technical Information (OSTI)

    of the conversion reaction in Mn3O4 lithium battery anodes Citation Details ... energy storage (including batteries and capacitors), hydrogen and fuel ...

  6. Phase stability of the SrMnO[subscript 3] hexagonal perovskite...

    Office of Scientific and Technical Information (OSTI)

    SrMnOsubscript 3 hexagonal perovskite system at high pressure and temperature Citation ... Country of Publication: United States Language: ENGLISH Word Cloud More Like This Full ...

  7. International Falls, MN Natural Gas Pipeline Imports From Canada (Dollars

    U.S. Energy Information Administration (EIA) Indexed Site

    per Thousand Cubic Feet) Dollars per Thousand Cubic Feet) International Falls, MN Natural Gas Pipeline Imports From Canada (Dollars per Thousand Cubic Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 1990's 1.71 2.03 2.00 2.33 2000's 2.77 4.85 3.01 -- -- 11.20 -- - = No Data Reported; -- = Not Applicable; NA = Not Available; W = Withheld to avoid disclosure of individual company data. Release Date: 08/31/2016 Next Release Date: 09/30/2016 Referring Pages:

  8. International Falls, MN Natural Gas Pipeline Imports From Canada (Million

    U.S. Energy Information Administration (EIA) Indexed Site

    Cubic Feet) Million Cubic Feet) International Falls, MN Natural Gas Pipeline Imports From Canada (Million Cubic Feet) Decade Year-0 Year-1 Year-2 Year-3 Year-4 Year-5 Year-6 Year-7 Year-8 Year-9 1990's 6,373 6,544 6,103 4,857 2000's 3,022 617 602 0 0 22 0 - = No Data Reported; -- = Not Applicable; NA = Not Available; W = Withheld to avoid disclosure of individual company data. Release Date: 08/31/2016 Next Release Date: 09/30/2016 Referring Pages: U.S.

  9. Electrochemical performance studies of MnO{sub 2} nanoflowers recovered from spent battery

    SciTech Connect (OSTI)

    Ali, Gomaa A.M.; Tan, Ling Ling; Jose, Rajan; Yusoff, Mashitah M.; Chong, Kwok Feng

    2014-12-15

    Highlights: MnO{sub 2} is recovered from spent zinccarbon batteries as nanoflowers structure. Recovered MnO{sub 2} nanoflowers show high specific capacitance. Recovered MnO{sub 2} nanoflowers show stable electrochemical cycling up to 900 cycles. Recovered MnO{sub 2} nanoflowers show low resistance in EIS data. - Abstract: The electrochemical performance of MnO{sub 2} nanoflowers recovered from spent household zinccarbon battery is studied by cyclic voltammetry, galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy. MnO{sub 2} nanoflowers are recovered from spent zinccarbon battery by combination of solution leaching and electrowinning techniques. In an effort to utilize recovered MnO{sub 2} nanoflowers as energy storage supercapacitor, it is crucial to understand their structure and electrochemical performance. X-ray diffraction analysis confirms the recovery of MnO{sub 2} in birnessite phase, while electron microscopy analysis shows the MnO{sub 2} is recovered as 3D nanostructure with nanoflower morphology. The recovered MnO{sub 2} nanoflowers exhibit high specific capacitance (294 F g{sup ?1} at 10 mV s{sup ?1}; 208.5 F g{sup ?1} at 0.1 A g{sup ?1}) in 1 M Na{sub 2}SO{sub 4} electrolyte, with stable electrochemical cycling. Electrochemical data analysis reveal the great potential of MnO{sub 2} nanoflowers recovered from spent zinccarbon battery in the development of high performance energy storage supercapacitor system.

  10. Lattice Mn3+ Behaviors in Li4Ti5O12/LiNi0.5Mn1.5O4 Full Cells

    SciTech Connect (OSTI)

    Zheng, Jianming; Xiao, Jie; Nie, Zimin; Zhang, Jiguang

    2013-05-28

    High voltage spinels LiNi0.5Mn1.5O4 (LNMO) with different contents of residual Mn3+ ions have been evaluated in full cells using Li4Ti5O12 (LTO) as standard anode. Greatly improved cycling stability has been observed for all spinels in LTO-limited full cell, compared with those in LNMO-limited ones, while the underlying mechanisms are quite different. It has been discovered that the participation of active Mn3+ in the extended cycling and thus its observable contribution to Li+ diffusion kinetics depend on the limiting electrode and the sufficiency of Li+ ions. Potential Mn dissolution has also been discussed to identify the key factors that need to be considered to construct full cells employing high voltage spinel as the cathode.

  11. Magnetic and structural properties of Zn doped MnV{sub 2}O{sub 4}

    SciTech Connect (OSTI)

    Shahi, Prashant; Shukla, K. K.; Singh, Rahul; Chatterjee, Sandip; Das, A.; Ghosh, A. K.; Nigam, A. K.

    2014-04-24

    The magnetization, Neutron diffraction and X-ray diffraction of Zn doped MnV{sub 2}O{sub 4} as a function of temperature have been measured. It has been observed, with increase of Zn the non-linear orientation of Mn spins with the V spins will decrease which effectively decrease the structural transition temperature more rapidly than Curie Temperature.

  12. Spin correlations and electron transport in MnBi:Au films

    SciTech Connect (OSTI)

    Kharel, P.; Skomski, R.; Sellmyer, D. J.

    2011-04-01

    The structural, magnetic, and electron transport properties of Mn{sub 55-x}Au{sub x}Bi{sub 45} (x = 0, 4.5) thin films prepared by magnetron sputtering have been investigated. The magnetization of the MnBi films decreases and the coercivity increases due to Au doping. The temperature dependence of resistivity between 2 to 300 K shows that the films are metallic but the 4.5% Au-doped film shows a Kondo behavior with resistance minimum at 10.2 K. The magnetoresistance is anisotropic and the positive transverse magnetoresistance is significantly enhanced (16.3% at 70 kOe) by Au doping. We interpret these data in terms of a model in which Au atoms preferentially substitute for Mn atoms on the Mn lattice, and some Mn atoms are displaced to interstitial sites in the NiAs structure. These interstitial Mn atoms are coupled antiferromagnetically to the Mn atoms on the original Mn lattice leading to the large decrease in magnetization, Kondo effect, and the positive magnetoresistance.

  13. Room temperature spin-polarizations of Mn-based antiferromagnetic nanoelectrodes

    SciTech Connect (OSTI)

    Yamada, Toyo Kazu; Vazquez de Parga, Amadeo L.

    2014-11-03

    Antiferromagnets produce no stray field, and therefore, a tip electrode made of antiferromagnetic material has been considered to be the most suitable choice to measure such as magnetoresistance (MR) through single isolated magnetic nanoparticles, molecules, and ultrathin films. Spin polarizations (P) of antiferromagnetic 3-nm, 6-nm, and annealed 3-nm Mn films grown on W tips with a bcc(110) apex as well as bulk-NiMn tips were obtained at 300?K by measuring MR in ultrahigh vacuum by means of spin-polarized scanning tunneling microscopy using a layerwise antiferromagnetically stacking bct-Mn(001) film electrode. The Mn-coated tips with coverages of 3 and 6?nm exhibited P values of 1??1% and 3??2%, respectively, which tips likely contain ?- or strained Mn. With a thermal assist, the crystalline quality and the magnetic stability of the film could increase. The annealed tip exhibited P?=?9??2%. The bulk-NiMn tips exhibit spin polarizations of 0 or 6??2% probably depending on the chemical species (Mn or Ni) present at the apex of the tip. Fe-coated W tips were used to estimate the bct-Mn(001) film spin polarization.

  14. Site Determination and Magnetism of Mn Doping in Protein Encapsulated Iron Oxide Nanoparticles

    SciTech Connect (OSTI)

    Pool, V.; Klem, M.; Jolley, J.; Arenholz, E.A.; Douglas, T.; Young, M.; Idzerda, Y.U.

    2010-01-11

    Soft-X-ray absorption spectroscopy, soft-X-ray magnetic circular dichroism, and alternating current magnetic susceptibility were performed on 6.7 nm iron oxide nanoparticles doped with (5-33%) Mn grown inside the horse-spleen ferritin protein cages and compared to similarly protein encapsulated pure Fe-oxide and Mn-oxide nanoparticles to determine the site of the Mn dopant and to quantify the magnetic behavior with varying Mn concentration. The Mn dopant is shown to substitute preferentially as Mn{sup +2} and prefers the octahedral site in the defected spinel structure. The Mn multiplet structure for the nanoparticles is simpler than for the bulk standards, suggesting that the nanoparticle lattices are relaxed from the distortions present in the bulk. Addition of Mn is found to alter the host Fe-oxide lattice from a defected ferrimagnetic spinel structure similar to {gamma}-Fe{sub 2}O{sub 3} to an non-ferromagnetic spinel structure with a local Fe environment similar to Fe{sub 3}O{sub 4}.

  15. Impedance studies of the thin film LiMn2O4/electrolyteinterface

    SciTech Connect (OSTI)

    Striebel, Kathryn A.; Sakai, E.; Cairns, Elton J.

    2001-04-07

    Room-temperature impedance measurements of a thin-film LiMn2O4/LiPF6-EC-DMC interface have been used to identify the spontaneous formation Li2Mn2O4 at the interface at room temperature at voltages of 3.7 and higher. The impedance of the LiMn2O4 films exhibited two time constants: at about 14 kHz and 60 to 200 Hz. The high frequency loop is dependent on film morphology and was attributed to the substrate/oxide interface. The low frequency behavior was dependent on both state-of-charge (SOC) and time at a given SOC. At full charge the impedance in this electrolyte was stable at room temperature over several days. At high lithium contents, film OCV and impedance tended to grow logarithmically with time, with lower rates for lower Mn3+ content in the film. The increased impedance was removed by oxidation of the film to 4.5V vs. Li/Li+. The observations are consistent with a reversible disproportionation of part of the LiMn2O4 into Li2Mn2O4 and a lithium-deficient spinel. With extended constant current cycling part of the Li2Mn2O4 degrades to the Mn2O3 and the process is no longer reversible.

  16. Electric-Field Modulation of Curie Temperature in (Ga, Mn)As Field-Effect Transistor Structures with Varying Channel Thickness and Mn Compositions

    SciTech Connect (OSTI)

    Nishitani, Y.; Endo, M.; Chiba, D.; Matsukura, F.; Ohno, H.

    2010-01-04

    We have investigated the change of T{sub C} of ferromagnetic semiconductor (Ga, Mn)As by changing hole concentration p. The field effect transistor structure was utilized to change p. The relation T{sub C}propor top{sup 0.2} is obtained for three samples, despite the difference of their Mn composition and thickness, indicating that the relation holds over 2 decades of p.

  17. K and Mn co-doped BaCd{sub 2}As{sub 2}: A hexagonal structured...

    Office of Scientific and Technical Information (OSTI)

    K and Mn co-doped BaCdsub 2Assub 2: A hexagonal structured bulk diluted magnetic semiconductor with large magnetoresistance Citation Details In-Document Search Title: K and Mn ...

  18. Scanning tunneling microscopy reveals LiMnAs is a room temperature anti-ferromagnetic semiconductor

    SciTech Connect (OSTI)

    Wijnheijmer, A. P.; Koenraad, P. M.; Marti, X.; Holy, V.; Cukr, M.; Novak, V.; Jungwirth, T.

    2012-03-12

    We performed scanning tunneling microscopy and spectroscopy on a LiMnAs(001) thin film epitaxially grown on an InAs(001) substrate by molecular beam epitaxy. While the in situ cleavage exposed only the InAs(110) non-polar planes, the cleavage continued into the LiMnAs thin layer across several facets. We combined both topography and current mappings to confirm that the facets correspond to LiMnAs. By spectroscopy we show that LiMnAs has a band gap. The band gap evidenced in this study, combined with the known Neel temperature well above room temperature, confirms that LiMnAs is a promising candidate for exploring the concepts of high temperature semiconductor spintronics based on antiferromagnets.

  19. Magnetic properties and photoabsorption of the Mn-doped CeO{sub 2} nanorods

    SciTech Connect (OSTI)

    Xia, Chuanhui; Science College of Chongqing Jiaotong University, Chongqing 400074 ; Hu, Chenguo; Chen, Peng; Wan, Buyong; He, Xiaoshan; Tian, Yongshu; Chongqing Communication College, Chongqing 400035

    2010-07-15

    Mn-doped CeO{sub 2} nanorods have been prepared from CeO{sub 2} particles through a facile composite-hydroxide-mediated (CHM) approach. The analysis from X-ray photoelectron spectroscopy indicates that the manganese doped in CeO{sub 2} exists as Mn{sup 2+}. The magnetic measurement of the Mn-doped CeO{sub 2} nanorods exhibits an enhanced ferromagnetic property at room temperature with a remanence magnetization (Mr) of 1.36 x 10{sup -3} emu/g and coercivity (Hc) of 22 Oe. Comparative UV-visible spectra reveal the shift of the absorption peak of the CeO{sub 2} from ultraviolet region to visible light region after being doped with Mn. The room temperature ferromagnetic properties and light absorption of the Mn-doped CeO{sub 2} nanorods would have potential applications in photocatalysis and building of photovoltaic devices.

  20. Giant atomic displacement at a magnetic phase transition in metastable Mn3O4

    SciTech Connect (OSTI)

    Hirai, Shigeto; Moreira Dos Santos, Antonio F; Shapiro, Max C; Molaison, Jamie J; Pradhan, Neelam; Guthrie, Malcolm; Tulk, Christopher A; Fisher, Ian R; Mao, Wendy

    2013-01-01

    We present x-ray, neutron scattering, and heat capacity data that reveal a coupled first-order magnetic and structural phase transition of the metastable mixed-valence postspinel compound Mn3O4 at 210 K. Powder neutron diffraction measurements reveal a magnetic structure in which Mn3+ spins align antiferromagnetically along the edge-sharing a axis, with a magnetic propagation vector k = [1/2,0,0]. In contrast, the Mn2+ spins, which are geometrically frustrated, do not order until a much lower temperature. Although the Mn2+ spins do not directly participate in the magnetic phase transition at 210 K, structural refinements reveal a large atomic shift at this phase transition, corresponding to a physical motion of approximately 0.25 angstrom, even though the crystal symmetry remains unchanged. This "giant" response is due to the coupled effect of built-in strain in the metastable postspinel structure with the orbital realignment of the Mn3+ ion.

  1. Category:WH Mapathan Todo List | Open Energy Information

    Open Energy Info (EERE)

    (Utility Company) City of Hallettsville, Texas (Utility Company) C cont. City of Hope, Arkansas (Utility Company) City of Wall Lake, Iowa (Utility Company) City of Warroad,...

  2. Ferromagnetic (Ga,Mn)As nanostructures for spintronic applications

    SciTech Connect (OSTI)

    Wosinski, Tadeusz; Andrearczyk, Tomasz; Figielski, Tadeusz; Makosa, Andrzej; Wrobel, Jerzy; Sadowski, Janusz

    2013-12-04

    Magneto-resistive, cross-like nanostructures have been designed and fabricated by electron-beam lithography patterning and chemical etching from thin epitaxial layers of the ferromagnetic semiconductor (Ga,Mn)As. The nanostructures, composed of two perpendicular nanostripes crossing in the middle of their length, represent four-terminal devices, in which an electric current can be driven through any of the two nanostripes. In these devices, a novel magneto-resistive memory effect, related to a rearrangement of magnetic domain walls in the central part of the device, has been demonstrated. It consists in that the zero-field resistance of a nanostripe depends on the direction of previously applied magnetic field. The nanostructures can thus work as two-state devices providing basic elements of nonvolatile memory cells.

  3. Impedance analysis of MnCoCuO NTC ceramic

    SciTech Connect (OSTI)

    Song, S.G. . E-mail: song-ph0@wpmail.paisley.ac.uk; Ling, Z.; Placido, F.

    2005-07-12

    Impedance spectroscopy is often used to analyse the electrical properties of ceramic materials having high-resistive grain boundaries, such as ZnO and SrTiO{sub 3}. Fewer attempts have been made at using this technique for the analysis of inhomogeneous electronic ceramics consisting of grains with differing composition, such as those occurring in negative temperature coefficient (NTC) thermistors. In this study, we have attempted to adopt ac impedance spectroscopy together with other techniques to analyse an NTC thermistor ceramic material. An Mn, Co and Cu multielements transition metal oxide (MnCoCuO) ceramic was prepared by using homogeneous precipitation employing oxalic acid. This material displayed a typical NTC effect, showing an electrical resistance decrease with temperature when dc electrical measurement was performed. The ac impedance spectroscopy analysis showed that there were two peaks in impedance and conductance versus frequency plot. By using an alternative representation of impedance spectra Z'/f versus Z', three distinct relaxation frequency ranges were identified. They are believed to originate, respectively, from the electrode, phase 1 (rich-Cu phase) and phase 2 (poor-Cu phase) grains existing in this ceramic. SEM observation and EDX analysis clearly showed existence of two distinct phase grains. The resistance values were derived from phases 1 and 2 grains based on ac impedance data. The sum of the resistance values was in good agreement with that from dc measurement in the temperature range of 30-95 deg. C. The material constant, B, for the two phases was also calculated, giving 3100 and 3600 K for phases 1 and 2, respectively.

  4. Ab initio study of Fe{sub 2}MnZ (Al, Si, Ge) Heusler alloy using GGA approximation

    SciTech Connect (OSTI)

    Jain, Vivek Kumar Jain, Vishal Lakshmi, N. Venugopalan, K.

    2014-04-24

    Density functional theory based on FP-LAPW method used to investigate the electronic structure of Fe{sub 2}MnZ, shows that the total spin magnetic moment shows a trend consistent with the Slater–Pauling curve. The Fe and Mn magnetic moment depend on choice of Z element although the magnetic moment of Z element is negative and less than 0.1 μ{sub B}. Spin polarization calculations evidence 100% spin polarization for Fe{sub 2}MnSi. Fe{sub 2}MnAl and Fe{sub 2}MnGe show metallic behavior with 93%, 98% spin polarization.

  5. Quantum Anomalous Hall Effect in Hg_1-yMn_yTe Quantum Wells

    SciTech Connect (OSTI)

    Liu, Chao-Xing; Qi, Xiao-Liang; Dai, Xi; Fang, Zhong; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg{sub 1-y}Mn{sub y}Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the Mn atoms, and the quantized Hall conductance is predicted for a range of quantum well thickness and the concentration of the Mn atoms. This effect enables dissipationless charge current in spintronics devices.

  6. Recent progress of magnetocaloric effect and magnetic refrigerant materials of Mn compounds (invited)

    SciTech Connect (OSTI)

    Wada, H. Takahara, T.; Katagiri, K.; Ohnishi, T.; Soejima, K.; Yamashita, K.

    2015-05-07

    Magnetocaloric and related properties of Ru and Ni substituted (MnFe){sub 2}(PSi) are presented. It is found that Ru and Ni are effective doping elements to reduce the thermal hysteresis of (MnFe){sub 2}(PSi). The origin of the thermal hysteresis is discussed on the basis of a thermodynamic model. It is shown that the elastic energy is responsible for the thermal hysteresis. We also show recent developments of the production process of Mn compounds in an industrial scale.

  7. Unoccupied electronic structure of Ni2MnGa ferromagnetic shape memory alloy

    SciTech Connect (OSTI)

    Maniraj, M.; D?Souza, S. W.; Rai, Abhishek; Schlagel, D. L.; Lograsso, T. A.; Chakrabarti, Aparna; Barman, S. R.

    2015-08-20

    Momentum resolved inverse photoemission spectroscopy measurements show that the dispersion of the unoccupied bands of Ni2MnGa is significant in the austenite phase. Furthermore, in the martensite phase, it is markedly reduced, which is possibly related to the structural transition to an incommensurate modulated state in the martensite phase. Finally, based on the first principle calculations of the electronic structure of NiMnGa, we show that the modification of the spectral shape with surface composition is related to change in the hybridization between the Mn 3d and Ni 3d-like states that dominate the unoccupied conduction band.

  8. Role of Cu-Ion Doping in Cu-α-MnO2 Nanowire Electrocatalysts for the Oxygen Reduction Reaction

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Davis, Danae J.; Lambert, Timothy N.; Vigil, Julian A.; Rodriguez, Mark A.; Brumbach, Michael T.; Coker, Eric N.; Limmer, Steven J.

    2014-07-09

    The role of Cu-ion doping in α-MnO2 electrocatalysts for the oxygen reduction reaction in alkaline electrolyte was investigated. Copper doped α-MnO2 nanowires (Cu-α-MnO2) were prepared with varying amounts of Cu2+ using a solvothermal method. The electrocatalytic dataindicates that Cu-α-MnO2 nanowires have higher terminal current densities, enhanced kinetic rate constants, and improved charge transfer resistances that trend with Cu-content, exceeding values attained by α-MnO2 alone. The observed improvement in catalytic behavior correlates with an increase in Mn3+ content for the Cu-α-MnO2 nanowires. The Mn3+/Mn4+ couple is themediator for the rate-limiting redox driven O2-/OH- exchange. It is proposed that O2 adsorbs viaanmore » axial site (the eg orbital on the Mn3+ d4 ion) at the surface, or at edge defects, of the nanowireand that the increase in covalent nature of the nanowire with Cu-ion doping leads to stabilization of O2 adsorbates and faster rates of reduction. This work is applicable to other manganese oxide electrocatalysts and shows for the first time there is a correlation for manganese oxides between electrocatalytic activity for the ORR in alkaline electrolyte and an increase in Mn3+ character of the oxide.« less

  9. Unique light-induced degradation in yellow-emitting K₂SiF₆:Mn²⁺ phosphor

    SciTech Connect (OSTI)

    Oyama, Takuya; Adachi, Sadao

    2014-10-07

    Photo-induced luminescence intensity degradation in yellow-emitting K₂SiF₆:Mn²⁺ phosphor is studied using x-ray diffraction measurement, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, PL decay analysis, and electron spin resonance (ESR) measurement. The yellow-emitting K₂SiF₆:Mn²⁺ phosphor exhibits remarkable degradation in the PL intensity under Xe lamp exposure. Coherent laser irradiation also induces degradation and its degree is in the order of He–Cd (λ = 325 nm) > Ar⁺ (488 nm) > He–Ne laser (632.8 nm). The degradation mechanism is proposed to be due to change in the valence state of manganese ions from Mn²⁺ to Mn³⁺ by the photooxidation (Mn²⁺ → Mn³⁺) or disproportionation reaction (2Mn²⁺ → Mn⁺ + Mn³⁺). The ESR measurement confirms the decreased Mn²⁺ spin density in the sample exposed with Xe lamp. The PLE spectrum suggests that the excitation of Mn³⁺ ions occurs through energy transfer upon absorption of exciting radiation by the Mn²⁺ ions. Thermal annealing of the degraded samples at ≥200 °C causes a blueshift in the PL emission band with an appearance of the Mn⁴⁺-related sharp red emission lines.

  10. Planar Hall effect in Y{sub 3}Fe{sub 5}O{sub 12}/IrMn films

    SciTech Connect (OSTI)

    Zhang, X. Zou, L. K.

    2014-12-29

    The planar Hall effect of IrMn on an yttrium iron garnet (YIG = Y{sub 3}Fe{sub 5}O{sub 12}) was measured in the magnetic field rotating in the film plane. The magnetic field angular dependence of planar Hall resistance (PHR) was observed in YIG/IrMn bilayer at different temperatures, while the Gd{sub 3}Ga{sub 5}O{sub 12}/IrMn film shows constant PHR for different magnetic field angles at both 10 K and 300 K. This provides evidence that IrMn has interfacial spins which can be led by ferrimagnetic layer in YIG/IrMn structure. A hysteresis can be observed in PHR-magnetic field angle loop of YIG/IrMn film at 10 K, indicative of the irreversible switching of IrMn interfacial spins at low temperature.

  11. First-principles study of spin-transfer torque in Co{sub 2}MnSi/Al/Co{sub 2}MnSi spin-valve

    SciTech Connect (OSTI)

    Tang, Ling Yang, Zejin

    2013-11-21

    The spin-transfer torque (STT) in Co{sub 2}MnSi(CMS)/Al/Co{sub 2}MnSi spin-valve system with and without interfacial disorder is studied by a first-principles noncollinear wave-function-matching method. It is shown that in the case of clean interface the angular dependence of STT for CoCo/Al (the asymmetry parameter Λ≈4.5) is more skewed than that for MnSi/Al (Λ≈2.9), which suggests the clean CoCo/Al architecture is much more efficient for the application on radio frequency oscillation. We also find that even with interfacial disorder the spin-valve of half-metallic CMS still has a relatively large parameter Λ compared to that of conventional ferromagnet. In addition, for clean interface the in-plane torkance of MnSi/Al is about twice as large as that of CoCo/Al. However, as long as the degree of interfacial disorder is sufficiently large, the CoCo/Al and MnSi/Al will show approximately the same magnitude of in-plane torkance. Furthermore, our results demonstrate that CMS/Al/CMS system has very high efficiency of STT to switch the magnetic layer of spin-valve.

  12. File:USDA-CE-Production-GIFmaps-MN.pdf | Open Energy Information

    Open Energy Info (EERE)

    MN.pdf Jump to: navigation, search File File history File usage Minnesota Ethanol Plant Locations Size of this preview: 776 600 pixels. Full resolution (1,650 1,275...

  13. Unoccupied electronic structure of Ni2MnGa ferromagnetic shape...

    Office of Scientific and Technical Information (OSTI)

    shape memory alloy This content will become publicly available on August 20, 2016 Prev Next Title: Unoccupied electronic structure of Ni2MnGa ferromagnetic shape memory alloy ...

  14. Microstructure and Mechanical Properties of Two-Phase Fe30Ni20Mn20Al30...

    Office of Scientific and Technical Information (OSTI)

    Title: Microstructure and Mechanical Properties of Two-Phase Fe30Ni20Mn20Al30 Alloy Authors: Wu, Xiaolan 1 ; Baker, Ian 1 ; Wu, H 1 ; Miller, Michael K 2 ; More, Karren ...

  15. Magnetocaloric effect of Pr2Fe17-x Mn x alloys (Journal Article...

    Office of Scientific and Technical Information (OSTI)

    SciTech Connect Search Results Journal Article: Magnetocaloric effect of Pr2Fe17-x Mn x ... OSTI Identifier: 1221829 Report Number(s): IS-J 8426 Journal ID: ISSN 1001-0521; PII: 134 ...

  16. Effect of Mn substitution on the transport properties of co-sputtered...

    Office of Scientific and Technical Information (OSTI)

    on the transport properties of co-sputtered Fesub 3-xMnsub xSi epilayers Citation Details In-Document Search Title: Effect of Mn substitution on the transport properties of ...

  17. X-Ray Spectroscopy of the Mn(4) Ca Cluster in the Water-Oxidation...

    Office of Scientific and Technical Information (OSTI)

    Ca Cluster in the Water-Oxidation Complex of Photosystem II Citation Details In-Document Search Title: X-Ray Spectroscopy of the Mn(4) Ca Cluster in the Water-Oxidation Complex ...

  18. Electrochemical Performances of LiMnPO4 Synthesized from Non...

    Office of Scientific and Technical Information (OSTI)

    Li1.1MnPO4 exhibits the most stable cycling ability probably because of the existence of a trace amount of Li3PO4 impurity that functions as a solid-state electrolyte on...

  19. Spectroscopic properties of (PVA+ZnO):Mn{sup 2+} polymer films

    SciTech Connect (OSTI)

    Rani, Ch.; Raju, D. Siva; Bindu, S. Hima; Krishna, J. Suresh; Raju, Ch. Linga

    2015-05-15

    Electron Paramagnetic Resonance (EPR), optical absorption and infrared spectral studies have been carried out on Mn{sup 2+} ions doped in poly(vinyl alcohol) complexed with zinc oxide polymer films prepared by solution cast technique. The EPR spectra of 1 mol% Mn{sup 2+} ions doped polymer complex (PVA+ZnO) at room temperature exhibit sextet hyperfine structure (hfs), centered at 2.01. The spin-Hamiltonian parameter values indicate that the ground state of Mn{sup 2+} ion in d{sup 5} and the site symmetry around Mn{sup 2+} ions in tetragonally distorted octa hedral site. The optical absorption spectra exhibits two bands centered at 275nm at 437nm. The FTIR spectrum exhibits bands characteristic of stretching and banding vibrations of O-H, C-H and C=C groups.

  20. Modeling and Characterization of the Magnetocaloric Effect in Ni2MnGa Materials

    SciTech Connect (OSTI)

    Nicholson, Don M; Odbadrakh, Khorgolkhuu; Rios, Orlando; Hodges, Jason P; Ludtka, Gerard Michael; Porter, Wallace D; Sefat, A. S.; Rusanu, Aurelian; Evans III, Boyd Mccutchen

    2012-01-01

    Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system have been explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering (LSMS) method to explore the magnetic states responsible for the magnet-caloric effect in this material. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy were investigated using differential scanning calorimetry (DSC) and superconducting quantum interference device (SQUID). Neutron scattering experiments were performed to observe the structural and magnetic phase transformations at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on alloys of Ni-Mn-Ga and Ni-Mn-Ga-Cu-Fe. Data from the observations are discussed in comparison with the computational studies.

  1. In-situ Electrical Conductivity of LixMnO2 Nanowires as a Function...

    Office of Scientific and Technical Information (OSTI)

    of LixMnO2 Nanowires as a Function of "x" and Size Authors: Le, Mya ; Liu, Yu ; Wang, Hui ; Dutta, Rajen ; Yan, Wenbo ; Hemminger, John C ; Wu, Ruqian ; Penner, Reginald...

  2. Pressure-Induced Metallization of the Mott Insulator MnO (Journal...

    Office of Scientific and Technical Information (OSTI)

    Pressure-Induced Metallization of the Mott Insulator MnO Citation ... Publication Date: 2004-01-12 OSTI Identifier: 15013737 Report Number(s): UCRL-JRNL-201933 Journal ID: ISSN ...

  3. Synthesis and characterization of MnPS{sub 3} for hydrogen sorption

    SciTech Connect (OSTI)

    Ismail, N.; Temerk, Y.M.; El-Meligi, A.A.; Badr, M.A.; Madian, M.

    2010-05-15

    Single phase MnPS{sub 3} powder was prepared by solid state reaction between Mn, S and P carried out at 650 deg. C in evacuated silica tube. The structure, morphology and sorption characteristics of the prepared solid were investigated. The results revealed that the obtained MnPS{sub 3} compound was capable of adsorbing 3.5 wt% hydrogen at -193 deg. C and a pressure of 30 bar. Little amount of hydrogen (0.07 wt%) was adsorbed at room temperature. The hydrogen adsorption/desorption cycles at various temperatures did not result in irreversible chemical structural changes of the MnPS{sub 3} compound, but the microstructure after hydrogen cycling diminished and became finer. - Graphical abstract: Atomic building of MPS{sub 3}

  4. Understanding the Structural and Electronic Evolution of Li2MnO3 During

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Electron Irradiation Via Electron Microscopy - Joint Center for Energy Storage Research November 17, 2014, Research Highlights Understanding the Structural and Electronic Evolution of Li2MnO3 During Electron Irradiation Via Electron Microscopy In-situ electron beam irradiation induces localized pockets of damage (a) and (b) characterized by the Mn atoms migrating to occupy Li sites, as shown in the annular bright field image of (c). This effect is clearly visible in an intensity line profile

  5. The role of C and Mn at the austenite/pearlite reaction front during non-steady-state pearlite growth in a Fe-C-Mn steel

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Aranda, M. M.; Rementeria, R.; Poplawsky, Jonathan D.; Urones-Garrote, E.; Capdevila, Carlos

    2015-04-18

    The role of C and Mn during the growth of pearlite under non-steady state conditions is analyzed by comparing the phase compositions of austenite, ferrite and cementite (γ+α+θ) through the use of transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and atom probe tomography (APT) measurements across the austenite/pearlite interface. Furthermore, a local Mn enrichment and C depletion at the austenite/pearlite interface has been measured, which causes a change in the driving force with time during divergent pearlite growth.

  6. The structure of the Caenorhabditis elegans manganese superoxide dismutase MnSOD-3-azide complex

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Hunter, Gary J.; Trinh, Chi H.; Bonetta, Rosalin; Stewart, Emma E.; Cabelli, Diane E.; Hunter, Therese

    2015-08-27

    C. elegans MnSOD-3 has been implicated in the longevity pathway and its mechanism of catalysis is relevant to the aging process and carcinogenesis. The structures of MnSOD-3 provide unique crystallographic evidence of a dynamic region of the tetrameric interface (residues 41–54). We have determined the structure of the MnSOD-3-azide complex to 1.77-Å resolution. The analysis of this complex shows that the substrate analog, azide, binds end-on to the manganese center as a sixth ligand and that it ligates directly to a third and new solvent molecule also positioned within interacting distance to the His30 and Tyr34 residues of the substratemore » access funnel. This is the first structure of a eukaryotic MnSOD-azide complex that demonstrates the extended, uninterrupted hydrogen-bonded network that forms a proton relay incorporating three outer sphere solvent molecules, the substrate analog, the gateway residues, Gln142, and the solvent ligand. This configuration supports the formation and release of the hydrogen peroxide product in agreement with the 5-6-5 catalytic mechanism for MnSOD. The high product dissociation constant k₄ of MnSOD-3 reflects low product inhibition making this enzyme efficient even at high levels of superoxide.« less

  7. Hydrothermal synthesis of Mn vanadate nanosheets and visible-light photocatalytic performance for the degradation of methyl blue

    SciTech Connect (OSTI)

    Pei, L.Z. Xie, Y.K.; Pei, Y.Q.; Jiang, Y.X.; Yu, H.Y.; Cai, Z.Y.

    2013-07-15

    Graphical abstract: - Highlights: Mn vanadate nanosheets have been synthesized by simple hydrothermal process. The formation of Mn vanadate nanosheets can be controlled by growth conditions. Mn vanadate nanosheets exhibit good photocatalytic activities for methyl blue. - Abstract: Mn vanadate nanosheets have been synthesized via a facile hydrothermal route using ammonium metavanadate and Mn acetate as the raw materials, polyvinyl pyrrolidone (PVP) as the surfactant. X-ray diffraction (XRD) shows that the Mn vanadate nanosheets are composed of monoclinic MnV{sub 2}O{sub 6} phase. Scanning electron microscopy (SEM) observation indicates that the nanosheets have the average thickness of about 50 nm, length of 210 ?m and width of 800 nm to 2 ?m. The growth process of the Mn vanadate nanosheets has also been discussed based on the analysis of the roles of the growth conditions on the formation of the Mn vanadate nanosheets. The nanosheets show good photocatalytic activities for the degradation of methylene blue (MB) under visible light irradiation. About 72.96% MB can be degraded after visible light irradiation for 1 h over 10 mg Mn vanadate nanosheets in 10 mL MB solution with the concentration of 10 mg L{sup ?1}.

  8. Inverse magnetocaloric effect in Mn{sub 2}NiGa and Mn{sub 1.75}Ni{sub 1.25}Ga magnetic shape memory alloys

    SciTech Connect (OSTI)

    Singh, Sanjay Barman, S. R.; Esakki Muthu, S.; Arumugam, S.; Senyshyn, A.; Rajput, P.; Suard, E.

    2014-02-03

    Inverse magnetocaloric effect is demonstrated in Mn{sub 2}NiGa and Mn{sub 1.75}Ni{sub 1.25}Ga magnetic shape memory alloys. The entropy change at the martensite transition is larger in Mn{sub 1.75}Ni{sub 1.25}Ga, and it increases linearly with magnetic field in both the specimens. Existence of inverse magnetocaloric effect is consistent with the observation that magnetization in the martensite phase is smaller than the austenite phase. Although the Mn content is smaller in Mn{sub 1.75}Ni{sub 1.25}Ga, from neutron diffraction, we show that the origin of inverse magnetocaloric effect is the antiferromagnetic interaction between the Mn atoms occupying inequivalent sites.

  9. The prominent role of oxygen in the multiferroicity of DyMnO3 and TbMnO3: a resonant soft x-ray scattering spectroscopy study

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    S. W. Huang; Lee, J. M.; Jeng, H. -T.; Shao, Y.; Wray, L. A.; Chen, J. M.; Qiao, R.; Yang, W. L.; Cao, Y.; Lin, J. -Y.; et al

    2016-07-21

    Oxygen is known to play an important role in the multiferroicity of rare earth manganites; however, how this role changes with rare earth elements is still not fully understood. To address this question, we have used resonant soft x-ray scattering spectroscopy to study the F-type (0; ; 0) diffraction peak from the antiferromagnetic order in DyMnO3 and TbMnO3. We focus on the measurements at O K-edge of these two manganites, supplemented by the results at Mn L2- and Dy M5-edge of DyMnO3. We show that the electronic states of di erent elements are coupled more strongly in DyMnO3 than inmore » TbMnO3, presumably due to the stronger lattice distortion and the tendency to develop E-type antiferromagnetism in the ferroelectric state that promote the orbital hybridization. We also show that the anomaly in the correlation length of (0; ; 0) peak in DyMnO3 signifies the exchange interaction between Mn and rare earth spins, which is absent in TbMnO3. Our findings reveal the prominent role of oxygen orbitals in the multiferroicity of rare earth manganites and the distinct energetics between them.« less

  10. Synthesis of spherical LiMnPO{sub 4}/C composite microparticles

    SciTech Connect (OSTI)

    Bakenov, Zhumabay; Taniguchi, Izumi

    2011-08-15

    Highlights: {yields} We could prepare LiMnPO{sub 4}/C composites by a novel preparation method. {yields} The LiMnPO{sub 4}/C composites were spherical particles with a mean diameter of 3.65 {mu}m. {yields} The LiMnPO{sub 4}/C composite cathode exhibited 112 mAh g{sup -1} at 0.05 C. {yields} It also showed a good rate capability up to 5 C at room temperature and 55 {sup o}C. -- Abstract: Spherical LiMnPO{sub 4}/C composite microparticles were prepared by a combination of spray pyrolysis and spray drying followed by heat treatment and examined as a cathode material for lithium batteries. The structure, morphology and electrochemical performance of the resulting spherical LiMnPO{sub 4}/C microparticles were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electronic microscopy and standard electrochemical techniques. The final sample was identified as a single phase orthorhombic structure of LiMnPO{sub 4} and spherical powders with a geometric mean diameter of 3.65 {mu}m and a geometric standard deviation of 1.34. The electrochemical cells contained the spherical LiMnPO{sub 4}/C microparticles exhibited first discharge capacities of 112 and 130 mAh g{sup -1} at 0.05 C at room temperature and 55 {sup o}C, respectively. These also showed a good rate capability up to 5 C at room temperature and 55 {sup o}C.

  11. Electron scattering mechanisms in Cu-Mn films for interconnect applications

    SciTech Connect (OSTI)

    Misjk, F.; Nagy, K. H.; Radnczi, G.; Lobotka, P.

    2014-08-28

    Electrical properties and corresponding structural features of Cu-Mn alloy films with potential application as barrier and interconnect layers were studied. Cu-Mn films were deposited by DC magnetron sputtering at room temperature on SiO{sub 2} substrates. Electrical resistivity measurements were made as a function of film composition and temperature. The specific resistivity varies linearly with the Mn content showing a maximum of 205???cm at 80 at. % Mn. The temperature coefficient of resistance (TCR) of all alloy films is low, showing non-metallic conductivity for most compositions. Also a minimum TCR has been observed in the 4080 at. % Mn range which was attributed to a magnetic transformation around 200300?K. Electrical resistivity measurements are correlated with the film structure revealed by transmission electron microscopy to clarify the phase regions throughout the composition range. In the 2040 at. % and 7080 at. % Mn ranges, two-phase structures were identified, where Cu- or Mn-rich solid solution grains were surrounded by a thin amorphous covering layer. Based on the revealed phase regions and morphologies electron scattering mechanisms in the system were evaluated by combining the Matthiessen's rule and the Mayadas-Schatzkes theory. Grain boundary reflectivity coefficients (r?=?0.60.8) were calculated from fitting the model to the measurements. The proposed model indicates that, in a binary system, the special arrangement of the two phases results in new scattering mechanisms. The results are of value in optimizing the various parameters needed to produce a suitable barrier layer.

  12. Peculiarly strong room-temperature ferromagnetism from low Mn-doping in ZnO grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Zuo Zheng; Morshed, Muhammad; Liu Jianlin; Beyermann, W. P.; Zheng Jianguo; Xin Yan

    2013-03-15

    Strong room-temperature ferromagnetism is demonstrated in single crystalline Mn-doped ZnO thin films grown by molecular beam epitaxy. Very low Mn doping concentration is investigated, and the measured magnetic moment is much larger than what is expected for an isolated ion based on Hund's rules. The ferromagnetic behavior evolves with Mn concentration. Both magnetic anisotropy and anomalous Hall effect confirm the intrinsic nature of ferromagnetism. While the Mn dopant plays a crucial role, another entity in the system is needed to explain the observed large magnetic moments.

  13. Mn-Stabilized Zirconia: From Imitation Diamonds to a New Potential High-T{sub C} Ferromagnetic Spintronics Material

    SciTech Connect (OSTI)

    Ostanin, S.; Ernst, A.; Sandratskii, L. M.; Bruno, P.; Daene, M.; Hergert, W.; Mertig, I.; Hughes, I. D.; Staunton, J. B.; Kudrnovsky, J.

    2007-01-05

    From the basis of ab initio electronic structure calculations which include the effects of thermally excited magnetic fluctuations, we predict Mn-stabilized cubic zirconia to be ferromagnetic above 500 K. We find this material, which is well known both as an imitation diamond and as a catalyst, to be half-metallic with the majority and minority spin Mn impurity states lying in zirconia's wide gap. The Mn concentration can exceed 40%. The high-T{sub C} ferromagnetism is robust to oxygen vacancy defects and to how the Mn impurities are distributed on the Zr fcc sublattice. We propose this ceramic as a promising future spintronics material.

  14. Properties of Ga{sub 1-x}Mn{sub x}As with high x (>0.1)

    SciTech Connect (OSTI)

    Chiba, D.; Yu, K. M.; Walukiewicz, W.; Nishitani, Y.; Matsukura, F.; Ohno, H.

    2008-04-01

    We have investigated the magnetic and the crystalline properties of a set of Ga{sub 1-x}Mn{sub x}As layers with high nominal Mn compositions (x=0.101-0.198). Magnetization measurements and combined channeling Rutherford backscattering (c-RBS) and particle induced x-ray emission (c-PIXE) measurements have been performed to determine the effective Mn composition x{sub eff} and the fraction of Mn atoms at various lattice sites. Here, x{sub eff} determined from magnetization measurements, which increases with increasing x, is consistent with the results determined from c-RBS-PIXE measurements.

  15. Enhanced ferromagnetic order in Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} featuring canted [MnO{sub 4}]{sub ∞} spin chains of mixed-valent Mn(III)/Mn(IV). Aliovalent substitution of the Sr{sub 4−x}Ln{sub x}Mn{sup III}{sub 2+x}Mn{sup IV}{sub 1−x}O{sub 3}(GeO{sub 4}){sub 3} solid-solution

    SciTech Connect (OSTI)

    West, J. Palmer; Sulejmanovic, Dino; Becht, Gregory; He, Jian; Hitchcock, Dale; Yan, Yonggao; Hwu, Shiou-Jyh

    2013-10-15

    Crystals of Sr{sub 4−x}Ln{sub x}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} (x=0; x∼0.15 for Ln=La, Pr, Nd, Sm. Eu, Gd, Dy; x∼0.3 for Ln=Gd) were isolated upon using high-temperature, solid-state methods in molten-salt media. These compounds are isostructural with the previously reported Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} (Ln=La, Sm, Gd) series that contains the same [MnO{sub 4}]{sub ∞} spin chains. The synthesis of the Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} (x=0) phase was carried out by a double aliovalent substitution with respect to the Sr{sup 2+} and Ge{sup 4+} ions that replace Na{sup +}/Ln{sup 3+} and As{sup 5+} in Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}, respectively. The title series contains mixed-valent Mn(III)/Mn(IV) and shows a limited range of solid solution, both of which were not observed in the previously reported Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} series. To form the Sr{sub 4−x}Ln{sub x}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} solid solution, one of the Sr{sup 2+} sites, i.e., the original Ln-site in Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}, is partially substituted by Ln{sup 3+} in a statistical disorder of Sr{sub 1−x}/Ln{sub x}. Initial magnetic investigations of selected derivatives reveal higher ferromagnetic ordering temperatures than those reported for the Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} series, presumably attributed to a lesser degree of canting as a result of introducing non-Jahn–Teller Mn{sup 4+} ions. Also intriguing is the observation of multiple anomalies at low temperatures which appear to be of electronic origins. - Graphical abstract: Sr{sub 4−x}Ln{sub x}Mn(III){sub 2+x}Mn(IV){sub 1−x}O{sub 3}(GeO{sub 4}){sub 3}. Display Omitted - Highlights: • Double aliovalent substitution: Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} with respect to Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}. • Solid solution with respect to statistical disorder of Sr{sub 1

  16. Comparison of LiMnPO4 made by Combustion and Hydrothermal Syntheses

    SciTech Connect (OSTI)

    Chen, Jiajun; Doeff, Marca M.; Wang, Ruigang

    2008-05-15

    Among the olivine-structured metal phosphate family, LiMnPO{sub 4} exhibits a high discharge potential (4V), which is still compatible with common electrolytes, making it interesting for use in the next generation of Li ion batteries. The extremely low electronic conductivity of this material severely limits its electrochemical performance, however. One strategy to overcome this limitation is to make LiMnPO{sub 4} nanoparticulate to decrease the diffusion distance. Another is to add a carbon or other conductive coating in intimate contact with the nanoparticles of the main phase, as is commonly done with LiFePO{sub 4}. The electrochemical performance of LiFePO{sub 4} is highly dependent on the quality of the carbon coatings on the particles [1-2], among other variables. Combustion synthesis allows the co-synthesis of nanoparticles coated with carbon in one step. Hydrothermal synthesis is used industrially to make LiFePO{sub 4} cathode materials [3] and affords a good deal of control over purity, crystallinity, and particle size. A wide range of olivine-structured materials has been successfully prepared by this technique [4], including LiMnPO{sub 4} in this study. In this paper, we report on the new synthesis of nano-LiMnPO{sub 4} by a combustion method. The purity is dependent upon the conditions used for synthesis, including the type of fuel and precursors that are chosen. The fuel to nitrate ratio influences the combustion temperature, which determines the type and amount of carbon found in the LiMnPO{sub 4} composites. This can further be modified by use of carbon structural modifiers added during a subsequent (optional) calcination step. Figure 1 shows a transmission electron microscopy (TEM) image of the spherical nano-sized LiMnPO{sub 4} particles typically formed by combustion synthesis. The average particle size is around 30 nm, in agreement with values obtained by the Rietveld refinement of XRD patterns. The small size of the particles cause the peak

  17. Comparison of LiMnPO4 made by Combustion and Hydrothermal Syntheses

    SciTech Connect (OSTI)

    Chen, Jiajun; Doeff, Marca M.; Wang, Ruigang

    2008-10-12

    Among the olivine-structured metal phosphate family, LiMnPO{sub 4} exhibits a high discharge potential (4V), which is still compatible with common electrolytes, making it interesting for use in the next generation of Li ion batteries. The extremely low electronic conductivity of this material severely limits its electrochemical performance, however. One strategy to overcome this limitation is to make LiMnPO{sub 4} nanoparticulate to decrease the diffusion distance. Another is to add a carbon or other conductive coating in intimate contact with the nanoparticles of the main phase, as is commonly done with LiFePO{sub 4}. The electrochemical performance of LiFePO{sub 4} is highly dependent on the quality of the carbon coatings on the particles, among other variables. Combustion synthesis allows the co-synthesis of nanoparticles coated with carbon in one step. Hydrothermal synthesis is used industrially to make LiFePO{sub 4} cathode materials and affords a good deal of control over purity, crystallinity, and particle size. A wide range of olivine-structured materials has been successfully prepared by this technique, including LiMnPO{sub 4} in this study. In this paper, we report on the new synthesis of nano-LiMnPO{sub 4} by a combustion method. The purity is dependent upon the conditions used for synthesis, including the type of fuel and precursors that are chosen. The fuel to nitrate ratio influences the combustion temperature, which determines the type and amount of carbon found in the LiMnPO{sub 4} composites. This can further be modified by use of carbon structural modifiers added during a subsequent (optional) calcination step. Figure 1 shows a transmission electron microscopy (TEM) image of the spherical nano-sized LiMnPO{sub 4} particles typically formed by combustion synthesis. The average particle size is around 30 nm, in agreement with values obtained by the Rietveld refinement of XRD patterns. The small size of the particles cause the peak broadening evident

  18. Disorder dependent half-metallicity in Mn{sub 2}CoSi inverse Heusler alloy

    SciTech Connect (OSTI)

    Singh, Mukhtiyar; Saini, Hardev S.; Thakur, Jyoti; Reshak, Ali H.; Kashyap, Manish K.

    2013-12-15

    Heusler alloys based thin-films often exhibit a degree of atomic disorder which leads to the lowering of spin polarization in spintronic devices. We present ab-initio calculations of atomic disorder effects on spin polarization and half-metallicity of Mn{sub 2}CoSi inverse Heusler alloy. The five types of disorder in Mn{sub 2}CoSi have been proposed and investigated in detail. The A2{sub a}-type and B2-type disorders destroy the half-metallicity whereas it sustains for all disorders concentrations in DO{sub 3a}- and A2{sub b}-type disorder and for smallest disorder concentration studied in DO{sub 3b}-type disorder. Lower formation energy/atom for A2{sub b}-type disorder than other four disorders in Mn{sub 2}CoSi advocates the stability of this disorder. The total magnetic moment shows a strong dependence on the disorder and the change in chemical environment. The 100% spin polarization even in the presence of disorders explicitly supports that these disorders shall not hinder the use of Mn{sub 2}CoSi inverse Heusler alloy in device applications. - Graphical abstract: Minority-spin gap (E{sub g↓}) and HM gap (E{sub sf}) as a function of concentrations of various possible disorder in Mn{sub 2}CoSi inverse Heusler alloy. The squares with solid line (black color)/dotted line (blue color)/dashed line (red color) reperesents E{sub g↓} for DO{sub 3a}-/DO{sub 3b}-/A2{sub b}-type disorder in Mn{sub 2}CoSi and the spheres with solid line (black color)/dottedline (blue color)/dashed line (red color) represents E{sub sf} for DO{sub 3a}-/DO{sub 3b}-/A2{sub b}-type disorder in Mn{sub 2}CoSi. - Highlights: • The DO{sub 3}- and A2-type disorders do not affect the half-metallicity in Mn{sub 2}CoSi. • The B2-type disorder solely destroys half-metallicity in Mn{sub 2}CoSi. • The A2-type disorder most probable to occur out of all three types. • The total spin magnetic moment strongly depends on the disorder concentrations.

  19. Novel Solar Energy Conversion Materials by Design of Mn(II) Oxides

    SciTech Connect (OSTI)

    Lany, S.; Peng, H.; Ndione, P.; Zakutayev, A.; Ginley, D. S.

    2013-01-01

    Solar energy conversion materials need to fulfill simultaneously a number of requirements in regard of their band-structure, optical properties, carrier transport, and doping. Despite their desirable chemical properties, e.g., for photo-electrocatalysis, transition-metal oxides usually do not have desirable semiconducting properties. Instead, oxides with open cation d-shells are typically Mott or charge-transfer insulators with notoriously poor transport properties, resulting from large effective electron/hole masses or from carrier self-trapping. Based on the notion that the electronic structure features (p-d interaction) supporting the p-type conductivity in d10 oxides like Cu2O and CuAlO2 occurs in a similar fashion also in the d5 (high-spin) oxides, we recently studied theoretically the band-structure and transport properties of the prototypical binary d5 oxides MnO and Fe2O3 [PRB 85, 201202(R)]. We found that MnO tends to self-trap holes by forming Mn+III, whereas Fe2O3 self-traps electrons by forming Fe+II. However, the self-trapping of holes is suppressed by when Mn is tetrahedrally coordinated, which suggests specific routes to design novel solar conversion materials by considering ternary Mn(II) oxides or oxide alloys. We are presenting theory, synthesis, and initial characterization for these novel energy materials.

  20. Magnetic susceptibilities of liquid Cr-Au, Mn-Au and Fe-Au alloys

    SciTech Connect (OSTI)

    Ohno, S.; Shimakura, H.; Tahara, S.; Okada, T.

    2015-08-17

    The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr{sub 1-c}Au{sub c} with 0.5 ≤ c and Mn{sub 1-c}Au{sub c} with 0.3≤c obeyed the Curie-Weiss law with regard to their dependence of χ on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of χ for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of χ for liquid Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of χ{sub 3d} due to 3d electrons for liquid binary TM-M (M=Au, Al, Si, Sb), and investigated the relationship between χ{sub 3d} and E{sub F} in liquid binary TM-M alloys at a composition of 50 at% TM.

  1. Extended magnetic exchange interactions in the high-temperature ferromagnet MnBi

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Christianson, Andrew D.; Hahn, Steven E.; Fishman, Randy Scott; Parker, David S.; McGuire, Michael A.; Sales, Brian C.; Lumsden, Mark D.; Williams, T. J.; Taylor, A. E.

    2016-05-09

    Here, the high-temperature ferromagnet MnBi continues to receive attention as a candidate to replace rare-earth-containing permanent magnets in applications above room temperature. This is due to a high Curie temperature, large magnetic moments, and a coercivity that increases with temperature. The synthesis of MnBi also allows for crystals that are free of interstitial Mn, enabling more direct access to the key interactions underlying the physical properties of binary Mn-based ferromagnets. In this work, we use inelastic neutron scattering to measure the spin waves of MnBi in order to characterize the magnetic exchange at low temperature. Consistent with the spin reorientationmore » that occurs below 140~K, we do not observe a spin gap in this system above our experimental resolution. A Heisenberg model was fit to the spin wave data in order to characterize the long-range nature of the exchange. It was found that interactions up to sixth nearest neighbor are required to fully parameterize the spin waves. Surprisingly, the nearest-neighbor term is antiferromagnetic, and the realization of a ferromagnetic ground state relies on the more numerous ferromagnetic terms beyond nearest neighbor, suggesting that the ferromagnetic ground state arises as a consequence of the long-ranged interactions in the system.« less

  2. High-Resolution Structure of the Photosynthetic Mn4Ca Catalyst from X-ray Spectroscopy

    SciTech Connect (OSTI)

    Yachandra, Vittal; Yano, Junko; Kern, Jan; Pushkar, Yulia; Sauer, Kenneth; Glatzel, Pieter; Bergmann, Uwe; Messinger, Johannes; Zouni, Athina; Yachandra, Vittal K.

    2007-08-01

    The application of high-resolution X-ray spectroscopy methods to study the photosynthetic water oxidizing complex, which contains a unique hetero-nuclear catalytic Mn4Ca cluster, are described. Issues of X-ray damage especially at the metal sites in the Mn4Ca cluster are discussed. The structure of the Mn4Ca catalyst at high-resolution which has so far eluded attempts of determination by X-ray diffraction, EXAFS and other spectroscopic techniques has been addressed using polarized EXAFS techniques applied to oriented PS II membrane preparations and PS II single crystals. A review of how the resolution of traditional EXAFS techniques can be improved, using methods such as range-extended EXAFS is presented, and the changes that occur in the structure of the cluster as it advances through the catalytic cycle are described. X-ray absorption and emission techniques (XANES and K? emission) have been used earlier to determine the oxidation states of the Mn4Ca cluster, and in this report we review the use of X-ray resonant Raman spectroscopy to understand the electronic structure of the Mn4Ca cluster as it cycles through the intermediate S-states.

  3. Electronic structure and the origin of the Dzyaloshinskii-Moriya interaction in MnSi

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Satpathy, S.; Shanavas, K. V.

    2016-05-02

    Here, the metallic helimagnet MnSi has been found to exhibit skyrmionic spin textures when subjected to magnetic fields at low temperatures. The Dzyaloshinskii-Moriya (DM) interaction plays a key role in stabilizing the skyrmion state. With the help of first-principles calculations, crystal field theory and a tight-binding model we study the electronic structure and the origin of the DM interaction in the B20 phase of MnSi. The strength ofmore » $$\\vec{D}$$ parameter is determined by the magnitude of the spin-orbit interaction and the degree of orbital mixing, induced by the symmetry-breaking distortions in the B20 phase. We find that, strong coupling between Mn-$d$ and Si-$p$ states lead to a mixed valence ground state $$|d^{7-x}p^{2+x}\\rangle$$ configuration. The experimental magnetic moment of $$0.4~\\mu_B$$ is consistent with the Coulomb-corrected DFT+$U$ calculations, which redistributes electrons between the majority and minority spin channels. We derive the magnetic interaction parameters $J$ and $$\\vec{D}$$ for Mn-Si-Mn superexchange paths using Moriya's theory assuming the interaction to be mediated by $e_g$ electrons near the Fermi level. Using parameters from our calculations, we get reasonable agreement with the observations.« less

  4. Elasticity and magnetocaloric effect in MnFe4Si3

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Herlitschke, Marcus; Klobes, B.; Sergueev, I.; Hering, Paul; Persson, Joerg; Hermann, Raphael P.

    2016-03-16

    The room temperature magnetocaloric material MnFe4Si3 was investigated with nuclear inelastic scattering (NIS) and resonant ultrasound spectroscopy (RUS) at different temperatures and applied magnetic fields in order to assess the infuence of the magnetic transition and the magnetocaloric effect on the lattice dynamics. The NIS data give access to phonons with energies above 3 meV, whereas RUS probes the elasticity of the material in the MHz frequency range and thus low energy, ~5 neV, phonon modes. A significant infuence of the magnetic transition on the lattice dynamics is observed only in the low energy region. Here, MnFe4Si3 and other compoundsmore » in the Mn5-xFexSi3 series were also investigated with vibrating sample magnetometry, resistivity measurements and Moessbauer spectroscopy in order to study the magnetic transitions and to complement the obtained results on the lattice dynamics.« less

  5. Electronic structural and magnetic properties of Mn{sub 5}Ge{sub 3} clusters

    SciTech Connect (OSTI)

    Yuan, H. K.; Chen, H. Kuang, A. L.; Tian, C. L.; Wang, J. Z.

    2013-11-28

    Theoretical understanding of the stability, ferromagnetism, and spin polarization of Mn{sub 5}Ge{sub 3} clusters has been performed by using the density functional theory with generalized gradient approximation for exchange and correlation. The magnetic moments and magnetic anisotropy energy (MAE) have been calculated for both bulk and clusters, and the enhanced magnetic moment as well as the enlarged MAE have been identified in clusters. The most attractive achievement is that Mn{sub 5}Ge{sub 3} clusters show a fine half-metallic character with large energy scales. The present results may have important implications for potential applications of small Mn{sub 5}Ge{sub 3} clusters as both emerging spintronics and next-generation data-storage technologies.

  6. Theoretical study on the role of dynamics on the unusual magnetic properties in MnBi

    SciTech Connect (OSTI)

    Shanavas, K. V.; Parker, David; Singh, David J.

    2014-11-27

    Here we study the electronic structure and lattice dynamics in the ferromagnet MnBi using first-principles calculations and a tight-binding model. The band structure around the Fermi level is dominated by Bi-p states which are the primary contributors to the magnetic anisotropy energy in the low temperature structure. A tight-binding model consisting of Mn-d and Bi-p states is developed and the parameters are determined from first-principles calculations. Phonon dispersions and elastic moduli exhibit several interesting features. In conclusion, the results imply that the magnetic interaction with the crystal lattice in MnBi is considerably more complex than previously thought and in particular that there is a rich interplay between phonons and magnetism involving both magnetoelastic and magnetostrictive coupling.

  7. Theoretical study on the role of dynamics on the unusual magnetic properties in MnBi

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Shanavas, K. V.; Parker, David; Singh, David J.

    2014-11-27

    Here we study the electronic structure and lattice dynamics in the ferromagnet MnBi using first-principles calculations and a tight-binding model. The band structure around the Fermi level is dominated by Bi-p states which are the primary contributors to the magnetic anisotropy energy in the low temperature structure. A tight-binding model consisting of Mn-d and Bi-p states is developed and the parameters are determined from first-principles calculations. Phonon dispersions and elastic moduli exhibit several interesting features. In conclusion, the results imply that the magnetic interaction with the crystal lattice in MnBi is considerably more complex than previously thought and in particularmore » that there is a rich interplay between phonons and magnetism involving both magnetoelastic and magnetostrictive coupling.« less

  8. Anomalous magnetic configuration of Mn{sub 2}NiAl ribbon and the role of hybridization in the martensitic transformation of Mn{sub 50}Ni{sub 50−x}Al{sub x} ribbons

    SciTech Connect (OSTI)

    Zhao, R. B.; Zhao, D. W.; Li, G. K.; Ma, L. E-mail: houdenglu@mail.hebtu.edu.cn; Zhen, C. M.; Hou, D. L. E-mail: houdenglu@mail.hebtu.edu.cn; Wang, W. H.; Liu, E. K.; Chen, J. L.; Wu, G. H.

    2014-12-08

    The magnetic configuration of Mn{sub 2}NiAl ribbon has been investigated. In contrast to Ni{sub 2}MnAl, the compound Mn{sub 2}NiAl with considerable disorder does exhibit ferromagnetism and, due to exchange interaction competition, both ferromagnetic and antiferromagnetic moment orientations can coexist between nearest neighbor Mn atoms. This is unexpected in Heusler alloys. Regarding the mechanism of the martensitic transformation in Mn{sub 50}Ni{sub 50−x}Al{sub x}, it is found that increasing the Al content results in an unusual change in the lattice constant, a decrease of the transformation entropy change, and enhancement of the calculated electron localization. These results indicate that the p-d covalent hybridization between Mn (or Ni) and Al atoms gradually increases at the expense of the d-d hybridization between Ni and Mn atoms. This leads to an increased stability of the austenite phase and a decrease of the martensitic transformation temperature. For 11 ≤ x ≤ 14, Mn{sub 50}Ni{sub 50−x}Al{sub x} ferromagnetic shape memory alloys are obtained.

  9. Enhanced performance of branched TiO{sub 2} nanorod based Mn-doped CdS and Mn-doped CdSe quantum dot-sensitized solar cell

    SciTech Connect (OSTI)

    Kim, Soo-Kyoung; Gopi, Chandu V. V. M.; Lee, Jae-Cheol; Kim, Hee-Je

    2015-04-28

    TiO{sub 2} branched nanostructures could be efficient as photoanodes for quantum dot-sensitized solar cells (QDSCs) due to their large surface area for QD deposition. In this study, Mn-doped CdS/Mn-doped CdSe deposited branched TiO{sub 2} nanorods were fabricated to enhance the photovoltaic performance of QDSCs. Mn doping in CdS and CdSe retards the recombination losses of electrons, while branched TiO{sub 2} nanorods facilitate effective electron transport and compensate for the low surface area of the nanorod structure. As a result, the charge-transfer resistance (R{sub CT}), electron lifetime (?{sub e}), and the amount of QD deposition were significantly improved with branched TiO{sub 2} nanorod based Mn-doped CdS/Mn-doped CdSe quantum dot-sensitized solar cell.

  10. Fabrication of (Mn,Co)3O4 Surface Coatings onto Alloy Substrates

    SciTech Connect (OSTI)

    Yang, Zhenguo; Xia, Guanguang; Li, Xiaohong S.; Singh, Prabhakar; Stevenson, Jeffry W.

    2007-04-30

    Ferritic stainless steels are promising candidates for IT-SOFC interconnect applications due to their low cost and resistance to oxidation at SOFC operating temperatures. However, several challenges remain, including long term electrical conductivity and surface stability under interconnect exposure conditions and chromia scale evaporation. One means of extending interconnect lifetime and improving performance is to apply a protective coating, such as (Mn,Co)3O4 spinel, to the cathode side of the interconnect. These coatings have proven effective in reducing scale growth kinetics and Cr volatility. This report describes several procedures developed at PNNL for fabricating (Mn,Co)3O4 spinel coatings onto ferritic stainless steels.

  11. Unoccupied electronic structure of Ni2MnGa ferromagnetic shape memory alloy

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Maniraj, M.; D׳Souza, S. W.; Rai, Abhishek; Schlagel, D. L.; Lograsso, T. A.; Iowa State Univ., Ames, IA; Chakrabarti, Aparna; Barman, S. R.

    2015-08-20

    Momentum resolved inverse photoemission spectroscopy measurements show that the dispersion of the unoccupied bands of Ni2MnGa is significant in the austenite phase. Furthermore, in the martensite phase, it is markedly reduced, which is possibly related to the structural transition to an incommensurate modulated state in the martensite phase. Finally, based on the first principle calculations of the electronic structure of Ni–Mn–Ga, we show that the modification of the spectral shape with surface composition is related to change in the hybridization between the Mn 3d and Ni 3d-like states that dominate the unoccupied conduction band.

  12. Study of lattice dynamics in yttrium doped NdMnO{sub 3} using Raman spectroscopy

    SciTech Connect (OSTI)

    Yadav, Ruchika Elizabeth, Suja; Nair, Harikrishnan S.

    2014-04-24

    A systematic study of Raman spectra on Yttrium doped NdMnO{sub 3} polycrystalline samples was undertaken to understand the lattice dynamics in this compound. Raman active phonons were analyzed and the observed peak were assigned to elucidate various phonon modes in the range (200 - 800) cm{sup −1}. It was observed that at 325 cm{sup −1} phonon frequency shifts upward as much as upto 4 % with increase in Yttrium content. Lattice distortions manifest themselves by frequency shifts in both bending and tilt modes of MnO{sub 6} octahedra, resulting in increase of Raman band line-widths.

  13. Antiferromagentic resonance detected by direct current voltages in MnF{sub 2}/Pt bilayers

    SciTech Connect (OSTI)

    Ross, Philipp; Schreier, Michael Lotze, Johannes; Huebl, Hans; Goennenwein, Sebastian T. B.; Gross, Rudolf

    2015-12-21

    We performed coplanar waveguide-based broadband ferromagnetic resonance experiments on the antiferromagnetic insulator MnF{sub 2}, while simultaneously recording the DC voltage arising in a thin platinum film deposited onto the MnF{sub 2}. The antiferromagnetic resonance is clearly reflected in both the transmission through the waveguide as well as the DC voltage in the Pt strip. The DC voltage remains largely unaffected by field reversal and thus presumably stems from microwave rectification and/or heating effects. However, we identify a small magnetic field orientation dependent contribution, compatible with antiferromagnetic spin pumping theory.

  14. Graphene in proximity to magnetic insulating LaMnO{sub 3}

    SciTech Connect (OSTI)

    Cheng, Guanghui; Wei, Laiming, E-mail: laiming@ustc.edu.cn, E-mail: cgzeng@ustc.edu.cn; Cheng, Long; Liang, Haixing; Zhang, Xiaoqiang; Li, Hui [Hefei National Laboratory for Physical Sciences at the Microscale (HFNL) and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Yu, Guolin [Shanghai Institute of Technical Physics, Chinese Academy of Science, Shanghai 200083 (China); Zeng, Changgan, E-mail: laiming@ustc.edu.cn, E-mail: cgzeng@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at the Microscale (HFNL) and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); International Center for Quantum Design of Functional Materials (ICQD), HFNL, University of Science and Technology of China, Hefei, Anhui 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2014-09-29

    Proximity to functional substrates may enhance the coupling between the quantum degrees of freedom and thus develop nontrivial quantum effects in graphene. Here, we demonstrate the successful fabrication of graphene in proximity to atomically flat magnetic insulating LaMnO{sub 3} films. The insulating nature of the LaMnO{sub 3} films not only ensures the electronic transport only occur in the graphene layers but also allow them to serve as dielectric layers for gating. Transport measurements reveal anomalous behaviors, including asymmetrical longitudinal magnetoresistivity and nonlinear Hall effect. This work may pave a way toward the realization of intriguing quantum phases in graphene.

  15. Electron-hole asymmetry, Dirac fermions, and quantum magnetoresistance in BaMnBi2

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Li, Lijun; Wang, Kefeng; Graf, D.; Wang, Limin; Wang, Aifeng; Petrovic, C.

    2016-03-28

    Here, we report two-dimensional quantum transport and Dirac fermions in BaMnBi2 single crystals. BaMnBi2 is a layered bad metal with highly anisotropic conductivity and magnetic order below 290 K. Magnetotransport properties, nonzero Berry phase, small cyclotron mass, and the first-principles band structure calculations indicate the presence of Dirac fermions in Bi square nets. Quantum oscillations in the Hall channel suggest the presence of both electron and hole pockets, whereas Dirac and parabolic states coexist at the Fermi level.

  16. Orbital two-channel Kondo effect in epitaxial ferromagnetic L10-MnAl films

    Office of Scientific and Technical Information (OSTI)

    (Journal Article) | SciTech Connect Journal Article: Orbital two-channel Kondo effect in epitaxial ferromagnetic L10-MnAl films Citation Details In-Document Search Title: Orbital two-channel Kondo effect in epitaxial ferromagnetic L10-MnAl films The orbital two-channel Kondo effect displaying exotic non-Fermi liquid behaviour arises in the intricate scenario of two conduction electrons compensating a pseudo-spin-1/2 impurity of two-level system. Despite extensive efforts for several decades,

  17. Structural transformations in Mn{sub 2}NiGa due to residual stress

    SciTech Connect (OSTI)

    Singh, Sanjay; Maniraj, M.; D'Souza, S. W.; Barman, S. R.; Ranjan, R.

    2010-02-22

    Powder x-ray diffraction study of Mn{sub 2}NiGa ferromagnetic shape memory alloy shows the existence of a 7M monoclinic modulated structure at room temperature (RT). The structure of Mn{sub 2}NiGa is found to be highly dependent on residual stress. For higher stress, the structure is tetragonal at RT, and for intermediate stress it is 7M monoclinic. However, only when the stress is considerably relaxed, the structure is cubic, as is expected at RT since the martensitic transition temperature is 230 K.

  18. MnO spin-wave dispersion curves from neutron powder diffraction

    SciTech Connect (OSTI)

    Goodwin, Andrew L.; Dove, Martin T.; Tucker, Matthew G.; Keen, David A.

    2007-02-15

    We describe a model-independent approach for the extraction of spin-wave dispersion curves from powder neutron total scattering data. Our approach is based on a statistical analysis of real-space spin configurations to calculate spin-dynamical quantities. The RMCPROFILE implementation of the reverse Monte Carlo refinement process is used to generate a large ensemble of supercell spin configurations from MnO powder diffraction data collected at 100 K. Our analysis of these configurations gives spin-wave dispersion curves for MnO that agree well with those determined independently using neutron triple-axis spectroscopic techniques.

  19. Study of structural and electronic properties of Mn{sub 3}O{sub 4}

    SciTech Connect (OSTI)

    Kaur, Ramandeep Maitra, Tulika Nautiyal, Tashi

    2014-04-24

    Using density functional theory calculations we have examined the structural and electronic properties of magnetic spinel Mn{sub 3}O{sub 4}. We have optimized the structure (both volume and c/a ratio) within GGA. Then Coulomb correlations are included in the calculations to study the electronic properties. We observe that both the band gap and magnetic moment increase with the increase in Coulomb correlation due to the increased Jahn-Teller splitting and localization of the single e{sub g} electron of Mn{sup 3+}.

  20. Perpendicularly magnetized {tau}-MnAl (001) thin films epitaxied on GaAs

    SciTech Connect (OSTI)

    Nie, S. H.; Zhu, L. J.; Lu, J.; Pan, D.; Wang, H. L.; Yu, X. Z.; Xiao, J. X.; Zhao, J. H.

    2013-04-15

    Perpendicularly magnetized {tau}-MnAl films have been epitaxied on GaAs (001) by molecular-beam epitaxy. Crystalline quality and magnetic properties of the samples were strongly dependent on growth temperature. The highest coercivity of 10.7 kOe, saturation magnetization of 361.4 emu/cm{sup 3}, perpendicular magnetic anisotropy constant of 13.65 Merg/cm{sup 3}, and magnetic energy product of 4.44 MGOe were achieved. These tunable magnetic properties make MnAl films valuable as excellent and cost-effective alternative for not only high density perpendicular magnetic recording storage and spintronics devices but also permanent magnets.

  1. Modeling and Characterization of the Magnetocaloric Effect in Ni2MnGa Materials

    SciTech Connect (OSTI)

    Nicholson, Don M; Odbadrakh, Khorgolkhuu; Shassere, Benjamin; Rios, Orlando; Hodges, Jason P; Ludtka, Gerard Michael; Porter, Wallace D; Safa-Sefat, Athena; Rusanu, Aurelian; Brown, Greg; Evans III, Boyd Mccutchen

    2014-01-01

    Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system are explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering method. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy are investigated using differential scanning calorimetry and superconducting quantum interference device. Experiments are performed at the Spallation Neutron Source at Oak Ridge National Laboratory to observe the structural and magnetic phase transformations.

  2. Enlarged Mn 3s splitting and room-temperature ferromagnetism in epitaxially grown oxygen doped Mn{sub 2}N{sub 0.86} films

    SciTech Connect (OSTI)

    Meng, M.; Wu, S. X. Ren, L. Z.; Zhou, W. Q.; Wang, Y. J.; Wang, G. L.; Li, S. W.

    2014-11-07

    Single-phase and oxygen doped Mn{sub 2}N{sub 0.86} thin films have been grown on MgO (111) by plasma-assisted molecular beam epitaxy. The films grow under tensile strain and, remarkably, they show ferromagnetic-like interactions at low temperature and ferromagnetic ordering agreed well with the Bloch-law T{sup 3/2} at room-temperature. We further demonstrate the enlarged Mn 3s splitting (6.46 eV) and its possible relation to the observed ferromagnetism. Our study not only provide a strategy for further theoretical work on oxygen doped manganese nitrides, but also shed promising light on utilizing its room-temperature FM property to fabricate spintronic devices.

  3. Synthesis of MnO{sub 2}-graphene composites with enhanced supercapacitive performance via pulse electrodeposition under supergravity field

    SciTech Connect (OSTI)

    Liu, Tingting; Shao, Guangjie; Ji, Mingtong; Wang, Guiling

    2014-07-01

    A method of pulse electrodeposition under supergravity field was proposed to synthesize MnO{sub 2}-graphene composites. Supergravity is very efficient for promoting mass transfer and decreasing concentration polarization during the electrodeposition process. The synthesis was conducted on our homemade supergravity equipment. The strength of supergravity field depended on the rotating speed of the ring electrode. 3D flower like MnO{sub 2} spheres composed of nanoflakes were acquired when the rotating speed was 3000 rpm. Graphene nanosheets play as a role of conductive substrates for MnO{sub 2} growing. The composites are evaluated as electrode materials for supercapacitors. Electrochemical results show that the maximum specific capacitance of the MnO{sub 2}-graphene composite is 595.7 F g{sup ?1} at a current density of 0.5 A g{sup ?1}. In addition, the composite exhibits excellent cycle stability with no capacitance attenuation after 1000 cycles. The approach provides new ideas for developing supercapacitor electrode materials with high performance. - Graphical abstract: 3D flower like MnO{sub 2} spheres composed of nanoflakes were acquired at 3000 rpm. - Highlights: MnO{sub 2}-graphene composites were prepared by pulse electrodeposition under supergravity. 3D flower like MnO{sub 2} spheres are anchored on the graphene nanosheets. The MnO{sub 2}-graphene electrode exhibits a specific capacitance of 595.7 F g{sup ?1}.

  4. Growth of single-crystal {alpha}-MnO{sub 2} nanorods on multi-walled carbon nanotubes

    SciTech Connect (OSTI)

    Chen Yong; Liu Chenguang; Liu Chang; Lu Gaoqing; Cheng Huiming

    2007-11-06

    Single-crystal {alpha}-MnO{sub 2} nanorods were grown on multi-walled carbon nanotubes (MWNTs) in H{sub 2}SO{sub 4} aqueous solution. The morphology and microstructure of the composites were examined by transmission electron microscopy, high-resolution transmission electron microscopy (HRTEM), X-ray diffractometry and energy dispersive spectroscopy (EDS). The results show that {alpha}-MnO{sub 2} single-crystal nanorods with a mean diameter of 15 nm were densely grown on the surface of MWNTs. Those MWNTs/MnO{sub 2} composites were used as an electrode material for supercapacitors, and it was found that the supercapacitor performance using MWNTs/MnO{sub 2} composites was improved largely compared to that using pure MWNTs and {alpha}-MnO{sub 2} nanorod mechanically mixed with MWNTs.

  5. Low frequency sonochemical synthesis of nanoporous amorphous manganese dioxide (MnO{sub 2}) and adsorption of remazol reactive dye

    SciTech Connect (OSTI)

    Hasan, Siti Zubaidah; Yusop, Muhammad Rahimi; Othman, Mohamed Rozali

    2015-09-25

    Nanoporous amorphous-MnO{sub 2} was synthesized by sonochemical process (sonication) on the solid manganese (II) acetate tetrahydrate (Mn(CH{sub 3}COO){sub 2}.4H{sub 2}O) in 0.1 M KMnO{sub 4}. The product was characterized by X-ray diffraction (XRD), morphology of the material was scanned by Field Emission Scanning Electron Microscopy (FE-SEM) and absorptions of MnO{sub 2} bonding was characterized by Fourier Transform Infra-Red Spectrometer (FT-IR). Remazol reactive dye or Red 3BS, was used in the adsorption study using nanoporous amorphous-MnO{sub 2}. In batch experiment, 10 ppm of Remazol reactive dye was used and experiment was carried out at room temperature. Adsorption of Remazol dye on 0.2g synthesized nanoporous amorphous-MnO{sub 2} showed 99 – 100% decolorization.

  6. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel using Atom Probe Tomography

    SciTech Connect (OSTI)

    Pereloma, E. V.; Stohr, R A; Miller, Michael K; Ringer, S. P.

    2009-01-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe){sub 3}Ti and (Ni,Fe){sub 3}(Al,Mn) precipitates eventually form after isothermal aging for {approx}60 seconds. The morphology of the (Ni,Fe){sub 3}Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe){sub 3}(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe){sub 3}Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  7. X-ray absorption spectroscopy of Mn doped ZnO thin films prepared by rf sputtering technique

    SciTech Connect (OSTI)

    Yadav, Ashok Kumar; Jha, S. N.; Bhattacharyya, D.; Haque, Sk Maidul; Shukla, Dinesh; Choudhary, Ram Janay

    2015-11-15

    A set of r.f. sputter deposited ZnO thin films prepared with different Mn doping concentrations have been characterised by Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Spectroscopy (XANES) measurements at Zn, Mn and O K edges and at Mn L{sub 2,3} edges apart from long range structural characterisation by Grazing Incident X-ray Diffraction (GIXRD) technique. Magnetic measurements show room temperature ferromagnetism in samples with lower Mn doping which is however, gets destroyed at higher Mn doping concentration. The results of the magnetic measurements have been explained using the local structure information obtained from EXAFS and XANES measurements.

  8. Microstructures and Mechanical Properties of Compositionally Complex Co-free FeNiMnCr18 FCC Solid Solution Alloy

    SciTech Connect (OSTI)

    Wu, Zhenggang; Bei, Hongbin

    2015-01-01

    Recently,a structurally-simplebutcompositionally-complex FeNiCoMnCr highentropyalloywasfoundto haveexcellentmechanicalproperties(e.g.,highstrengthandductility).Tounderstandthepotentialof using highentropyalloysasstructuralmaterialsforadvancednuclearreactorandpowerplants,itis necessary tohaveathoroughunderstandingoftheirstructuralstabilityandmechanicalpropertiesde- gradation underneutronirradiation.ThisrequiresustodevelopasimilarmodelalloywithoutCobe- cause materialwithCowillmakepost-neutron-irradiationtestingdifficult duetotheproductionofthe 60Co radioisotope.Toachievethisgoal,aFCC-structuredsingle-phasealloywithacompositionof FeNiMnCr18 wassuccessfullydeveloped.Thisnear-equiatomicFeNiMnCr18 alloy hasgoodmalleability and itsmicrostructurecanbecontrolledbythermomechanicalprocessing.Byrollingandannealing,the as-cast elongated-grained-microstructureisreplacedbyhomogeneousequiaxedgrains.Themechanical properties (e.g.,strengthandductility)oftheFeNiMnCr18 alloy arecomparabletothoseoftheequiatomic FeNiCoMnCr highentropyalloy.Bothstrengthandductilityincreasewithdecreasingdeformation temperature,withthelargestdifferenceoccurringbetween293and77K.Extensivetwin-bandswhich are bundlesofnumerousindividualtwinsareobservedwhenitistensile-fracturedat77K.Notwin bands aredetectedbyEBSDformaterialsdeformedat293Kandhigher.Theunusualtemperature-de- pendencies ofUTSanduniformelongationcouldbecausedbythedevelopmentofthedensetwin substructure, twin-dislocationinteractionsandtheinteractionsbetweenprimaryandsecondarytwin- ning systemswhichresultinamicrostructurerefinement andhencecauseenhancedstrainhardening and postponednecking.

  9. MxMn8O16 (M = Ag or K) as promising cathode materials for secondary Mg based batteries: The role of the cation M

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Huang, Jianping; Takeuchi, Esther S.; Altug S. Poyraz; Takeuchi, Kenneth J.; Marschilok, Amy C.

    2016-02-15

    Here, AgxMn8O16 (Ag-OMS-2) and KxMn8O16 (K-OMS-2) were investigated as high voltage cathode materials for Mg based batteries. Both MxMn8O16 materials delivered high initial capacities (>180 mA h g–1), and KxMn8O16 showed high cycle stability with a reversible capacity of >170 mA h g–1 after 20 cycles.

  10. Bulk and surface half-metallicity: The case of D0{sub 3}-type Mn{sub 3}Ge

    SciTech Connect (OSTI)

    Liu, Hao; Gao, G. Y. Hu, Lei; Ni, Yun; Zu, Fengxia; Zhu, Sicong; Wang, Shuling; Yao, K. L.

    2014-01-21

    Motivated by the experimental realization of D0{sub 22}-type Mn{sub 3}Ge (001) films [Kurt et al. Appl. Phys. Lett. 101, 132410 (2012)] and the structural stability of D0{sub 3}-type Heusler alloy Mn{sub 3}Ge [Zhang et al. J. Phys.: Condens. Matter 25, 206006 (2013)], we use the first-principles calculations based on the full potential linearized augmented plane-wave method to investigate the electronic and magnetic properties of D0{sub 3}-type Heusler alloy Mn{sub 3}Ge and its (001) surface. We show that bulk D0{sub 3}-Mn{sub 3}Ge is a half-metallic ferromagnet with the minority-spin energy gap of 0.52 eV and the magnetic moment of 1.00 μ{sub B} per formula unit. The bulk half-metallicity is preserved at the pure Mn-terminated (001) surface due to the large exchange split, but the MnGe-terminated (001) surface destroys the bulk half-metallicity. We also reveal that the surface stabilities are comparable between the D0{sub 3}-Mn{sub 3}Ge (001) and the experimental D0{sub 22}-Mn{sub 3}Ge (001), which indicates the feasibility to grow the Mn{sub 3}Ge (001) films with D0{sub 3} phase other than D0{sub 22} one. The surface half-metallicity and stability make D0{sub 3}-Mn{sub 3}Ge a promising candidate for spintronic applications.

  11. Magnetochromic effect in multiferroic R In <mn>1mn> x Mn x O <mn>3mn> ( R = Tb , Dy)

    SciTech Connect (OSTI)

    Chen, P.; Holinsworth, B. S.; O'Neal, K. R.; Brinzari, T. V.; Mazumdar, D.; Topping, C. V.; Luo, X.; Cheong, S.-W.; Singleton, J.; McGill, S.; Musfeldt, J. L.

    2015-05-26

    We combined high field magnetization and magneto-optical spectroscopy to investigate spin-charge coupling in Mn-substituted rare-earth indium oxides of chemical formula RIn₁₋xMnxO₃ (R=Tb, Dy). The edge states, on-site Mn³⁺d to d excitations, and rare-earth f-manifold excitations all track the magnetization energy due to dominant Zeeman interactions. The field-induced modifications to the rare-earth excitations are quite large because spin-orbit coupling naturally mixes spin and charge, suggesting that the next logical step in the design strategy should be to bring spin-orbit coupling onto the trigonal bipyramidal chromophore site with a 4 or 5d center.

  12. Redox Dynamics of Mixed Metal (Mn, Cr, and Fe) Ultrafine Particles

    SciTech Connect (OSTI)

    Nico, Peter S.; Kumfer, Benjamin M.; Kennedy, Ian M.; Anastasio, Cort

    2008-08-01

    The impact of particle composition on metal oxidation state, and on changes in oxidation state with simulated atmospheric aging, are investigated experimentally in flame-generated nanoparticles containing Mn, Cr, and Fe. The results demonstrate that the initial fraction of Cr(VI) within the particles decreases with increasing total metal concentration in the flame. In contrast, the initial Mn oxidation state was only partly controlled by metal loading, suggesting the importance of other factors. Two reaction pathways, one reductive and one oxidative, were found to be operating simultaneously during simulated atmospheric aging. The oxidative pathway depended upon the presence of simulated sunlight and O{sub 3}, whereas the reductive pathway occurred in the presence of simulated sunlight alone. The reductive pathway appears to be rapid but transient, allowing the oxidative pathway to dominate with longer aging times, i.e. greater than {approx}8 hours. The presence of Mn within the particles enhanced the importance of the oxidative pathway, leading to more net Cr oxidation during aging implying that Mn can mediate oxidation by removal of electrons from other particulate metals.

  13. Short- and long-range magnetic order in LaMnAsO

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    McGuire, Michael A.; Garlea, Vasile Ovidiu

    2016-02-02

    The magnetic properties of the layered oxypnictide LaMnAsO have been revisited using neutron scattering and magnetization measurements. The present measurements identify the Néel temperature TN = 360(1) K. Below TN the critical exponent describing the magnetic order parameter is β=0.33–0.35 , consistent with a three-dimensional Heisenberg model. Above this temperature, diffuse magnetic scattering indicative of short-range magnetic order is observed, and this scattering persists up to TSRO = 650(10) K. Morevoer, the magnetic susceptibility shows a weak anomaly at TSRO and no anomaly at TN. Analysis of the diffuse scattering data using a reverse Monte Carlo algorithm indicates that abovemore » TN nearly two-dimensional, short-range magnetic order is present with a correlation length of 9.3(3) Å within the Mn layers at 400 K. The inelastic scattering data reveal a spin gap of 3.5 meV in the long-range ordered state, and strong, low-energy (quasielastic) magnetic excitations emerging in the short-range ordered state. When we compared it with other related compounds correlates the distortion of the Mn coordination tetrahedra to the sign of the magnetic exchange along the layer-stacking direction, and suggests that short-range order above TN is a common feature in the magnetic behavior of layered Mn-based pnictides and oxypnictides.« less

  14. On the structural defects in synthetic {gamma}-MnO{sub 2}s

    SciTech Connect (OSTI)

    Hill, L.I.; Verbaere, A. . E-mail: alain.verbaere@cnrs-imn.fr

    2004-12-01

    In the literature, the {gamma}-MnO{sub 2} structure is considered to be that of ramsdellite (R), in which two types of defects exist. The occurrence of a slab of pyrolusite (r) is named a De Wolff defect and random faults r in R give intergrowths of ramsdellite and pyrolusite, which account well for the global features of many experimental diffraction patterns. The other type of defect results from 'microtwinning', which allows the so-called {epsilon}-MnO{sub 2} to be put with {gamma}-MnO{sub 2} in the same classification. This paper discusses the previous models of defect and what could be the features of the 'microtwinning', giving for each possible model the corresponding expected features in reciprocal space. The results of a selected area electron diffraction study of rather well crystallized samples of {gamma}-MnO{sub 2} are presented. The splitting of particular diffraction spots and new diffuse intensity are interpreted as the first experimental evidence for 'microtwinning', and a model with orientation variants within microdomains embedded in a 'normal' structure is proposed, which is rather different from the previous hypotheses involving parallel twin planes and parallel twin boundaries.

  15. Ordering ferromagnetic In{sub 1?x}Mn{sub x}As quantum dots

    SciTech Connect (OSTI)

    Ferri, Fabio A.; Marega Jr, Euclydes; Kunets, Vasyl P.; Salamo, Gregory J.

    2013-12-04

    In this work, we present a method to order low temperature (LT) self-assembled ferromagnetic In{sub 1?x}Mn{sub x}As quantum dots (QDs) grown by molecular beam epitaxy (MBE). The ordered In{sub 1?x}Mn{sub x}As QDs were grown on top of a non-magnetic In{sub 0.4}Ga{sub 0.6}As/GaAs(100) QDs multi-layered structure. The modulation of the chemical potential, due to the stacking, provides a nucleation center for the LT In{sub 1?x}Mn{sub x}As QDs. For particular conditions, such as surface morphology and growth conditions, the In{sub 1?x}Mn{sub x}As QDs align along lines like chains. For comparison purposes, we also report the study of QDs grown on plain GaAs(100) substrates. Ferromagnetic behavior was observed for all structures at 2 K.

  16. CaMn2Sb2: Spin waves on a frustrated antiferromagnetic honeycomb lattice

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    McNally, D. E.; Simonson, J. W.; Kistner-Morris, J. J.; Smith, G. J.; Hassinger, J. E.; DeBeer-Schmidt, L.; Kolesnikov, A. I.; Zaliznyak, I.; Aronson, M. C.

    2015-05-22

    We present inelastic neutron scattering measurements of the antiferromagnetic insulator CaMn2Sb2:, which consists of corrugated honeycomb layers of Mn. The dispersion of magnetic excitations has been measured along the H and L directions in reciprocal space, with a maximum excitation energy of ≈ 24 meV. These excitations are well described by spin waves in a Heisenberg model, including first and second neighbor exchange interactions, J1 and J2, in the Mn plane and also an exchange interaction between planes. The determined ratio J2/J1 ≈ 1/6 suggests that CaMn2Sb2: is the first example of a compound that lies very close to themore » mean field tricritical point, known for the classical Heisenberg model on the honeycomb lattice, where the N´eel phase and two different spiral phases coexist. The magnitude of the determined exchange interactions reveal a mean field ordering temperature ≈ 4 times larger than the reported N´eel temperature TN = 85 K, suggesting significant frustration arising from proximity to the tricritical point.« less

  17. Modulation on Ni{sub 2}MnGa(001) surface

    SciTech Connect (OSTI)

    D'Souza, S. W.; Rai, Abhishek; Nayak, J.; Maniraj, M.; Dhaka, R. S.; Barman, S. R.; Schlagel, D. L.; Lograsso, T. A.

    2011-07-15

    We report periodic modulation on (001) surface of Ni2MnGa ferromagnetic shape memory alloy. For the stoichiometric surface, analysis of the low energy electron diffraction (LEED) spot profiles shows that the modulation is incommensurate. The modulation appears at 200 K, concomitant with the first order structural transition to the martensitic phase.

  18. Aliovalent titanium substitution in layered mixed Li Ni-Mn-Co oxides for lithium battery applications

    SciTech Connect (OSTI)

    Kam, Kinson; Doeff, Marca M.

    2010-12-01

    Improved electrochemical characteristics are observed for Li[Ni1/3Co1/3-yMyMn1/3]O2 cathode materials when M=Ti and y<0.07, compared to the baseline material, with up to 15percent increased discharge capacity.

  19. Helical antiferromagnetic ordering in Lu1-xScxMnSi

    SciTech Connect (OSTI)

    Goetsch, Ryan J; Anand, V K; Johnston, David C

    2014-08-01

    Polycrystalline samples of Lu1?xScxMnSi (x=0, 0.25, 0.5) are studied using powder x-ray diffraction, heat capacity Cp, magnetization, magnetic susceptibility ?, and electrical resistivity ? measurements versus temperature T and magnetic field H. This system crystallizes in the primitive orthorhombic TiNiSi-type structure (space group Pnma) as previously reported. The ?(T) data indicate metallic behavior. The Cp(T), ?(T), and ?(T) measurements consistently indicate long-range antiferromagnetic (AF) transitions with AF ordering temperatures TN=246, 215, and 188 K for x=0, 0.25, and 0.5, respectively. A second transition is observed at somewhat lower T for each sample from the ?(T) and ?(T) measurements, which we speculate are due to spin reorientation transitions; these second transitions are completely suppressed in H=5.5 T. The Cp data below 10 K for each composition indicate an enhanced Sommerfeld electronic heat capacity coefficient for the series in the range ?=2429 mJ/mol K2. The ?(T) measurements up to 1000 K were fitted by local-moment Curie-Weiss behaviors which indicate a low Mn spin S?1. The ? data below TN are analyzed using the Weiss molecular field theory for a planar noncollinear cycloidal AF structure with a composition-dependent pitch, following the previous neutron diffraction work of Venturini et al. [J. Alloys Compd. 256, 65 (1997)]. Within this model, the fits indicate a turn angle between Mn ordered moments along the cycloid axis of ?100? or ?145?, either of which indicate dominant AF interactions between the Mn spins in the Lu1?xScxMnSi series of compounds.

  20. Structural relationships between new carbide La{sub 14}Sn(MnC{sub 6}){sub 3} and fully ordered La{sub 11}(MnC{sub 6}){sub 3}

    SciTech Connect (OSTI)

    Zaikina, Julia V.; Zhou, Haidong; Latturner, Susan E.

    2010-12-15

    Crystals of the ternary La{sub 11}(MnC{sub 6}){sub 3} and new quaternary carbide La{sub 14}Sn(MnC{sub 6}){sub 3} phases were grown from La/Ni eutectic flux and their structures were determined by means of X-ray single crystal diffraction. La{sub 11}(MnC{sub 6}){sub 3} is a new superstructure variant of La{sub 3.67}MnC{sub 6} (previously reported disordered subcell: P6{sub 3}/m; a{sub 0}=8.806 A; c{sub 0}=5.329 A, Z=2). The superstructure (R3-bar ; a={radical}3a{sub 0}=15.2649(9) A; c=3c{sub 0}=16.013(1) A, Z=6; R{sub 1}=0.022) is realized by complete ordering of the La chains within the columns of face-sharing carbon octahedra, with alternating La-La distances leading to R-centering and enlargement of the unit cell. The structure of the quaternary carbide La{sub 14}Sn(MnC{sub 6}){sub 3} (P6-bar ; a=8.756(1) A; c=10.483(2) A, Z=1; R{sub 1}=0.026) is closely related to that of La{sub 11}(MnC{sub 6}){sub 3} with part of the MnC{sub 6} units replaced by Sn atoms. The structure and precise composition of La{sub 14}Sn(MnC{sub 6}){sub 3} can be derived from that of La{sub 11}(MnC{sub 6}){sub 3} by taking into account the extent of this substitution and variation in lanthanum siting in the chain of carbon octahedra. Band structure calculations indicate both phases are metallic; the La{sub 11}(MnC{sub 6}){sub 3} phase is stabilized by the ordering of La atoms which induces a pseudogap at E{sub F}. -- La{sub 11}(MnC{sub 6}){sub 3} with fully ordered superstructure and a new carbide La{sub 14}Sn(MnC{sub 6}){sub 3} were obtained from La/Ni eutectic flux. Display Omitted

  1. The effects of annealing on the microstructure and mechanical properties of Fe28Ni18Mn33Al21

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Meng, Fanling; Qiu, Jingwen; Baker, Ian; Bei, Hongbin

    2015-08-20

    In this paper, As-cast Fe28Ni18Mn33Al21, which consists of aligned, 50 nm, (Ni, Al)-rich B2, and (Fe, Mn)-rich f.c.c. phases, was annealed at a variety of temperatures up to 1423 K and the microstructure and mechanical properties were examined. It was shown that the as-cast microstructure arises from a eutectoid transformation at ~1300 K. Annealing at temperatures ≤1073 K produces β-Mn-structured precipitates and hardness values up to 816 HV, while annealing at temperatures >1073 K leads to dramatic coarsening of the two-phase B2/f.c.c. microstructure (up to 5.5 µm after 50 h at 1273 K), but does not lead to β-Mn precipitation.more » Interestingly, annealing at temperatures >1073 K delays the onset of β-Mn precipitation during subsequent anneals at lower temperatures. Coarsening the B2/f.c.c. lamellar structure by annealing at higher temperatures softens it and leads to increases in ductility from fracture before yield to ~8 % elongation. Finally, the presence of β-Mn precipitates makes the very fine, brittle B2/f.c.c. microstructures even more brittle, but significant ductility (8.4 % elongation) is possible even with β-Mn precipitates present if the B2/f.c.c. matrix is coarse and, hence, more ductile.« less

  2. X-ray and Raman spectroscopic studies on Ru substituted LiMn{sub 2}O{sub 4}

    SciTech Connect (OSTI)

    Kalavathi, S.; Ravindran, T. R.; Sahu, P. Ch.; Kalaivani, D.

    2015-06-24

    Phase pure Ru substituted LiMn{sub 2}O{sub 4} charge frustrated spinel compounds have been synthesized. Ru substitution for Mn is possible only up to 7.5%. Powder diffraction measurements confirm sustenance of charge frustrated cubic phase with space group Fd3m upon substitution of Ru for Mn. An increase in lattice parameter has been observed indicating replacement of Mn as Ru{sup 3+} or Ru{sup 4+} rather than Ru{sup 5+}. Raman spectroscopic measurements show that the crystal structure is robust against an increase of laser power and the observed bands show an expected red shift. In the case of Ru substituted LiMn{sub 2}O{sub 4}, the A{sub 1g} symmetric stretching mode, the F{sup (1)}{sub 2g} and the F{sup (2)}{sub 2g} symmetric bending modes identified with the Mn-O octahedra show a red shift up to Ru 0.075 and at higher Ru concentrations, revert back to the frequency corresponding to the pristine LiMn{sub 2}O{sub 4}.

  3. Structural and magnetic properties of magnetron sputtered Ni-Mn-Sn ferromagnetic shape memory alloy thin films

    SciTech Connect (OSTI)

    Vishnoi, Ritu; Kaur, Davinder

    2010-05-15

    In the present study, structural and magnetic properties of Mn-rich, off-stoichiometric, nanocrystalline Ni-Mn-Sn ferromagnetic shape memory alloy thin films, grown on Si (100) substrates at 550 deg. C by dc magnetron sputtering have been systematically investigated. The crystallization, surface morphology, and structural features were studied using x-ray diffraction, atomic force microscopy, and field emission scanning electron microscopy. The structural transition from austenite to martensite was observed with an increase of Mn content. Austenitic phase with mixed L2{sub 1}/A2+B2 structure has been observed at room temperature in Ni{sub 52.6}Mn{sub 23.7}Sn{sub 23.6} (S{sub 1}) and Ni{sub 51.5}Mn{sub 26.1}Sn{sub 22.2} (S{sub 2}) films, while those with composition of Ni{sub 58.9}Mn{sub 28.0}Sn{sub 13.0} (S{sub 3}) and Ni{sub 58.3}Mn{sub 29.0}Sn{sub 12.6} (S{sub 4}) show martensitic phase with 14M modulated monoclinic structures. Field induced martensite-austenite transformation has been observed in magnetization studies using superconducting quantum interference device magnetometer. Temperature dependent magnetization measurements demonstrate the influence of magnetic field on the structural phase transition temperature. The investigations reveal an increase of martensitic transformation temperature (T{sub M}) with corresponding increase in substitution of Mn. The films exhibit ferromagnetic behavior at low temperatures below Curie temperature (T{sub C}). The decrease in saturation moment with increasing Mn content, indicates the existence of antiferromagnetic correlations within ferromagnetic matrix.

  4. First-principles study on the ferrimagnetic half-metallic Mn{sub 2}FeAs alloy

    SciTech Connect (OSTI)

    Qi, Santao; Zhang, Chuan-Hui; Chen, Bao; Shen, Jiang; Chen, Nanxian

    2015-05-15

    Mn-based full-Heusler alloys are kinds of promising candidates for new half-metallic materials. Basing on first principles, the electronic structures and magnetic properties of the Mn{sub 2}FeAs full-Heusler alloy have been investigated in detail. The Hg{sub 2}CuTi-type Mn{sub 2}FeAs compound obeys the Slater-Pauling rule, while the anti-parallel alignment atomic magnetic moments of Mn locating at different sites indicate it a ferrimagnetic alloy. The calculated spin-down bands behave half-metallic character, exhibiting a direct gap of 0.46 eV with a 100% spin polarization at the Fermi level. More studies show the compound would maintain half-metallic nature in a large range of variational lattice constants. We expect that our calculated results may trigger Mn{sub 2}FeAs applying in the future spintronics field. - Graphical abstract: The d orbitals of Mn and Fe atoms split into multi-degenerated levels which create new bonding and nonbonding states. These exchange splitting shift the Fermi level to origin band gap.▪ - Highlights: • The electronic structure and magnetic properties of Mn{sub 2}FeAs full-Heusler alloy were studied. • A total magnetic moment of 3μ{sub B} was obtained for Mn{sub 2}FeAs alloy, following the SP rule M{sub t}=Z{sub t}−24. • The origin of ferrimagnetism and half-metallic character in Mn{sub 2}FeAs were discussed.

  5. Facile and template-free preparation of {alpha}-MnO{sub 2} nanostructures and their enhanced adsorbability

    SciTech Connect (OSTI)

    Ma, Hongwei; Shen, Jianfeng; Shi, Min; Yan, Bo; Li, Na; Ye, Mingxin

    2011-09-15

    Graphical abstract: . The as-obtained ({alpha}-MnO{sub 2}) nanomaterials could act as an adsorbent to remove Conge red. More significantly, the nanomaterials are nontoxic and environmentally friendly though a biological MTT assay experiment. Plots of the capacity to remove Conge red with time by the commercial and new-prepared {alpha}-MnO{sub 2}. Inset shows absorption of Congo Red with time by new-prepared rod-clusters {alpha}-MnO{sub 2} (0, 10, 20, 40 and 60 min, respectively). Highlights: {yields} Nanostructured {alpha}-MnO{sub 2} was prepared through a template-free hydrothermal method. {yields} The obtained {alpha}-MnO{sub 2} could act as effective adsorbents to remove organic dyes. {yields} The obtained adsorbents are environmentally friendly. -- Abstract: In this paper, nanostructured MnO{sub 2} materials were successfully prepared through a simple and template-free hydrothermal method. X-ray diffraction pattern indicates that the as-prepared nanomaterials are {alpha}-MnO{sub 2}. Transmission Electron Microscopy and Scanning Electron Microscopy images demonstrate that nanostructured rod-clusters {alpha}-MnO{sub 2} could be evolved from the nanorods. Brunauer-Emmett-Teller (BET) surface area measurement was employed to characterize the surface property. Moreover, the as-obtained ({alpha}-MnO{sub 2}) nanomaterials could act as an efficient adsorbent to remove Congo Red and Methlylene Blue. More significantly, the nanomaterials are nontoxic and environmentally friendly via biological methylthiazolyldiphenyltetrazoliumbromide assay experiments. Its nontoxic and enhanced adsorbability properties guarantee their safe applications in environmental protection and industrial aspects.

  6. Atomic moments in Mn{sub 2}CoAl thin films analyzed by X-ray magnetic circular dichroism

    SciTech Connect (OSTI)

    Jamer, M. E.; Assaf, B. A.; Heiman, D.; Sterbinsky, G. E.; Arena, D. A.

    2014-12-07

    Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn{sub 2}CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. The results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value.

  7. Atomic moments in Mn2CoAl thin films analyzed by X-ray magnetic circular dichroism

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Jamer, M. E.; Assaf, B. A.; Sterbinsky, G. E.; Arena, D. A.; Heiman, D.

    2014-12-05

    Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. Results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value.

  8. Large enhancement of Blocking temperature by control of interfacial structures in Pt/NiFe/IrMn/MgO/Pt multilayers

    SciTech Connect (OSTI)

    Chen, Xi; Wang, Shouguo Han, Gang; Jiang, Shaolong; Yang, Kang; Liu, Qianqian; Yu, Guanghua; Liu, Jialong; Wang, Rongming

    2015-09-15

    The Blocking temperature (T{sub B}) of Pt/NiFe/IrMn/MgO/Pt multilayers was greatly enhanced from far below room temperature (RT) to above RT by inserting 1 nm thick Mg layer at IrMn/MgO interface. Furthermore, the exchange bias field (H{sub eb}) was increased as well by the control of interfacial structures. The evidence for a significant fraction of Mn-O bonding at IrMn/MgO interface without Mg insertion layer was provided by X-ray photoelectron spectroscopy. The bonding between Mn and O can decrease the antiferromagnetism of IrMn film, leading to lower value of T{sub B} in Pt/NiFe/IrMn/MgO/Pt multilayers. Ultrathin Mg film inserted at IrMn/MgO interface acting as an oxygen sinking layer can suppress the oxidation reactions between Mn and O and reduce the formation of Mn-O bonding greatly. The oxidation suppression results in the recovery of the antiferromagnetism of IrMn film, which can enhance T{sub B} and H{sub eb}. Furthermore, the high resolution transmission electron microscopy demonstrates that the Mg insertion layer can efficiently promote a high-quality MgO (200) texture. This study will enhance the understanding of physics in antiferromagnet-based spintronic devices.

  9. Visible Light-Induced Electron Transfer from Di-mu-oxo Bridged Dinuclear Mn Complexes to Cr Centers in Silica Nanopores

    SciTech Connect (OSTI)

    Frei, Heinz; Weare, Walter W.; Pushkar, Yulia; Yachandra, Vittal K.; Frei, Heinz

    2008-06-03

    The compound (bpy)2MnIII(mu-O)2MnIV(bpy)2, a structural model relevant for the photosynthetic water oxidation complex, was coupled to single CrVI charge-transfer chromophores in the channels of the nanoporous oxide AlMCM-41. Mn K-edge EXAFS spectroscopy confirmed that the di-mu-oxo dinuclear Mn core of the complex is unaffected when loaded into the nanoscale pores. Observation of the 16-line EPR signal characteristic of MnIII(mu-O)2MnIV demonstrates that the majority of the loaded complexes retained their nascent oxidation state in the presence or absence of CrVI centers. The FT-Raman spectrum upon visible light excitation of the CrVI-OII --> CrV-OI ligand-to-metal charge-transfer reveals electron transfer from MnIII(mu-O)2MnIV (Mn-O stretch at 700 cm-1) to CrVI, resulting in the formation of CrV and MnIV(mu-O)2MnIV (Mn-O stretch at 645 cm-1). All initial and final states are directly observed by FT-Raman or EPR spectroscopy, and the assignments corroborated by X-ray absorption spectroscopy measurements. The endoergic charge separation products (DELTA Eo = -0.6 V) remain after several minutes, which points to spatial separation of CrV and MnIV(mu-O)2MnIV as a consequence of hole (OI) hopping as a major contributing mechanism. This is the first observation of visible light-induced oxidation of a potential water oxidation complex by a metal charge-transfer pump in a nanoporous environment. These findings will allow for the assembly and photochemical characterization of well defined transition metal molecular units, with the ultimate goal of performing endothermic, multi-electron transformations that are coupled to visible light electron pumps in nanostructured scaffolds.

  10. Penetration depth and absorption mechanisms of spin currents in Ir{sub 20}Mn{sub 80} and Fe{sub 50}Mn{sub 50} polycrystalline films by ferromagnetic resonance and spin pumping

    SciTech Connect (OSTI)

    Merodio, P.; Ghosh, A.; Lemonias, C.; Gautier, E.; Ebels, U.; Chshiev, M.; Béa, H. E-mail: helene.bea@cea.fr; Baltz, V. E-mail: helene.bea@cea.fr

    2014-01-20

    Spintronics relies on the spin dependent transport properties of ferromagnets (Fs). Although antiferromagnets (AFs) are used for their magnetic properties only, some fundamental F-spintronics phenomena like spin transfer torque, domain wall motion, and tunnel anisotropic magnetoresistance also occur with AFs, thus making AF-spintronics attractive. Here, room temperature critical depths and absorption mechanisms of spin currents in Ir{sub 20}Mn{sub 80} and Fe{sub 50}Mn{sub 50} are determined by F-resonance and spin pumping. In particular, we find room temperature critical depths originating from different absorption mechanisms: dephasing for Ir{sub 20}Mn{sub 80} and spin flipping for Fe{sub 50}Mn{sub 50}.

  11. U.S. Natural Gas Imports by Pipeline from Mexico

    Gasoline and Diesel Fuel Update (EIA)

    Argentina Sabine Pass, LA Total To Barbados Miami, FL Total To Brazil Freeport, TX Sabine Pass, LA Total to Canada Eastport, ID Calais, ME Detroit, MI Marysville, MI Port Huron, MI Crosby, ND Portal, ND Sault St. Marie, MI St. Clair, MI Noyes, MN Babb, MT Havre, MT Port of Morgan, MT Sherwood, ND Pittsburg, NH Buffalo, NY Grand Island, NY Massena, NY Niagara Falls, NY Waddington, NY Sumas, WA Sweetgrass, MT Total to Chile Sabine Pass, LA Total to China Kenai, AK Sabine Pass, LA Total to Egypt

  12. Influence of Mn concentration on magnetic topological insulator MnxBi2−xTe3 thin-film Hall-effect sensor

    SciTech Connect (OSTI)

    Ni, Y.; Zhang, Z.; Nlebedim, I. C.; Hadimani, R. L.; Jiles, D. C.

    2015-06-11

    Hall-effect (HE) sensors based on high-quality Mn-doped Bi2Te3 topological insulator (TI) thin films have been systematically studied in this paper. Improvement of Hall sensitivity is found after doping the magnetic element Mn into Bi2Te3. The sensors with low Mn concentrations, MnxBi2-xTe3, x = 0.01 and 0.08 show the linear behavior of Hall resistance with sensitivity about 5 Ω/T. And their Hall sensitivity shows weak dependence on temperature. For sensors with high Mn concentration (x = 0.23), the Hall resistance with respect to magnetic field shows a hysteretic behavior. Moreover, its sensitivity shows almost eight times as high as that of the HE sensors with low Mn concentration. The highest sensitivity can reach 43 Ω/T at very low magnetic field. This increase of Hall sensitivity is caused by the occurrence of anomalous HE (AHE) after ferromagnetic phase transition. Our work indicates that the magnetic-element-doped TIs with AHE are good candidates for HE sensors.

  13. Spintronic properties of Li1.5Mn0.5Z (Z=As, Sb) compounds in...

    Office of Scientific and Technical Information (OSTI)

    Publisher's Accepted Manuscript: Spintronic properties of Li1.5Mn0.5Z (ZAs, Sb) compounds in the Cu2Sb structure This content will become publicly available on January 26, 2017 ...

  14. Post-Growth Annealing of Bridgman-grown CdZnTe and CdMnTe Crystals...

    Office of Scientific and Technical Information (OSTI)

    Nuclear Radiation Detectors Citation Details In-Document Search Title: Post-Growth Annealing of Bridgman-grown CdZnTe and CdMnTe Crystals for Room-temperature Nuclear ...

  15. Thermoelectric properties of nano-meso-micro β-MnO₂ powders as a function of electrical resistance

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Hedden, Morgan; Francis, Nick; Haraldsen, Jason T.; Ahmed, Towfiq; Constantin, Costel

    2015-07-15

    Particle sizes of manganese oxide (β-MnO₂) powders were modified by using a mortar and pestle ground method for period of times that varied between 15–60 min. Particle size versus ground time clearly shows the existence of a size-induced regime transition (i.e., regime I and II). Thermoelectric properties of β-MnO₂ powders as a function of electrical resistance in the range of RP = 10 - 80Ω were measured. Based on the data presented, we propose a model for the β-MnO₂ system in which nanometer-scale MnO₂ crystallites bond together through weak van der Waals forces to form larger conglomerates that span inmore » size from nanometer to micrometer scale.« less

  16. Electronic properties of Mn-phthalocyanine–C{sub 60} bulk heterojunctions: Combining photoemission and electron energy-loss spectroscopy

    SciTech Connect (OSTI)

    Roth, Friedrich; Lupulescu, Cosmin; Darlatt, Erik; Gottwald, Alexander; Eberhardt, Wolfgang

    2015-11-14

    The electronic properties of co-evaporated mixtures (blends) of manganese phthalocyanine and the fullerene C{sub 60} (MnPc:C{sub 60}) have been studied as a function of the concentration of the two constituents using two supplementary electron spectroscopic methods, photoemission spectroscopy (PES) and electron energy-loss spectroscopy (EELS) in transmission. Our PES measurements provide a detailed picture of the electronic structure measured with different excitation energies as well as different mixing ratios between MnPc and C{sub 60}. Besides a relative energy shift, the occupied electronic states of the two materials remain essentially unchanged. The observed energy level alignment is different compared to that of the related CuPc:C{sub 60} bulk heterojunction. Moreover, the results from our EELS investigations show that, despite the rather small interface interaction, the MnPc related electronic excitation spectrum changes significantly by admixing C{sub 60} to MnPc thin films.

  17. Anti-site disorder and improved functionality of Mn?NiX (X = Al, Ga, In, Sn) inverse Heusler alloys

    SciTech Connect (OSTI)

    Paul, Souvik; Kundu, Ashis; Ghosh, Subhradip; Sanyal, Biplab

    2014-10-07

    Recent first-principles calculations have predicted Mn?NiX (X = Al, Ga, In, Sn) alloys to be magnetic shape memory alloys. Moreover, experiments on Mn?NiGa and Mn?NiSn suggest that the alloys deviate from the perfect inverse Heusler arrangement and that there is chemical disorder at the sublattices with tetrahedral symmetry. In this work, we investigate the effects of such chemical disorder on phase stabilities and magnetic properties using first-principles electronic structure methods. We find that except Mn?NiAl, all other alloys show signatures of martensitic transformations in presence of anti-site disorder at the sublattices with tetrahedral symmetry. This improves the possibilities of realizing martensitic transformations at relatively low fields and the possibilities of obtaining significantly large inverse magneto-caloric effects, in comparison to perfect inverse Heusler arrangement of atoms. We analyze the origin of such improvements in functional properties by investigating electronic structures and magnetic exchange interactions.

  18. Laser activation of ferromagnetism in hydrogenated Ga{sub 1-x}Mn{sub x}As

    SciTech Connect (OSTI)

    Farshchi, R.; Dubon, O. D.; Hwang, D. J.; Misra, N.; Grigoropoulos, C. P.; Ashby, P. D.

    2008-01-07

    We demonstrate the local depassivation of hydrogenated Ga{sub 1-x}Mn{sub x}As by pulsed-laser annealing. The controlled removal of Mn-H defect complexes, which form upon hydrogenation and render Mn acceptors inactive, is achieved by focused laser irradiation. As a result, regions of electrically and ferromagnetically active Ga{sub 1-x}Mn{sub x}As are formed within a nonactive, otherwise structurally identical film. The hydrogenated films subjected to blanket laser depassivation display a Curie temperature T{sub C} up to 60 K, or 60% of the T{sub C} of the as-grown films. These results demonstrate the direct laser writing of mesoscopic ferromagnetically active regions as a viable route for the realization of planar, nanoscale spintronic systems.

  19. What is the valence of Mn in Ga1-xMnxN?

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Berlijn, Tom; Jarrell, Mark; Nelson, Ryky; Ku, Wei; Moreno, Juana

    2015-11-04

    Motivated by the potential high Curie temperature of Ga1-xMnxN, we investigate the controversial Mn valence in this diluted magnetic semiconductor. From a first-principles Wannier-function analysis of the high energy Hilbert space, we find unambiguously the Mn valence to be close to 2+(d5), but in a mixed spin configuration with average magnetic moments of 4µB. By integrating out high-energy degrees of freedom differently, we further demonstrate the feasibility of both effective d4 and d5 descriptions. These two descriptions offer simple pictures for local and extended properties of the system, and highlight the dual nature of its doped hole. Specifically, in themore » effective d5 description, we demonstrate novel physical effects absent in previous studies. Thus, our derivation highlights the richness of low-energy sectors in interacting many-body systems and the generic need for multiple effective descriptions.« less

  20. Magnetochromic effect in multiferroic R In 1 ₋ x Mn x O 3 ( R = Tb , Dy)

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Chen, P.; Holinsworth, B. S.; O'Neal, K. R.; Brinzari, T. V.; Mazumdar, D.; Topping, C. V.; Luo, X.; Cheong, S.-W.; Singleton, J.; McGill, S.; et al

    2015-05-26

    We combined high field magnetization and magneto-optical spectroscopy to investigate spin-charge coupling in Mn-substituted rare-earth indium oxides of chemical formula RIn₁₋xMnxO₃ (R=Tb, Dy). The edge states, on-site Mn³⁺d to d excitations, and rare-earth f-manifold excitations all track the magnetization energy due to dominant Zeeman interactions. The field-induced modifications to the rare-earth excitations are quite large because spin-orbit coupling naturally mixes spin and charge, suggesting that the next logical step in the design strategy should be to bring spin-orbit coupling onto the trigonal bipyramidal chromophore site with a 4 or 5d center.

  1. Magnetostructural phase transformations in Tb 1-x Mn 2

    SciTech Connect (OSTI)

    Zou, Junding; Paudyal, Durga; Liu, Jing; Mudryk, Yaroslav; Pecharsky, Vitalij K.; Gschneidner, Karl A.

    2015-01-16

    Magnetism and phase transformations in non-stoichiometric Tb1-xMn2 (x = 0.056, 0.039) have been studied as functions of temperature and magnetic field using magnetization, heat capacity, and X-ray powder diffraction measurements. Lowering the temperature, the compounds sequentially order ferrimagnetically and antiferromagnetically, and finally, exhibit spin reorientation transitions. Moreover, these structural distortions from room temperature cubic to low temperature rhombohedral structures occur at TN, and are accompanied by large volume changes reaching ~-1.27% and -1.42%, respectively. First principles electronic structure calculations confirm the phase transformation from the ferrimagnetic cubic structure to the antiferromagnetic rhombohedral structure in TbMn2.

  2. Extrinsic anomalous Hall effect in epitaxial Mn{sub 4}N films

    SciTech Connect (OSTI)

    Meng, M.; Wu, S. X. Ren, L. Z.; Zhou, W. Q.; Wang, Y. J.; Wang, G. L.; Li, S. W.

    2015-01-19

    Anomalous Hall effect (AHE) in ferrimagnetic Mn{sub 4}N epitaxial films grown by molecular-beam epitaxy is investigated. The longitudinal conductivity σ{sub xx} is within the superclean regime, indicating Mn{sub 4}N is a highly conducting material. We further demonstrate that the AHE signal in 40-nm-thick films is mainly due to the extrinsic contributions based on the analysis fitted by ρ{sub AH}=a′ρ{sub xx0}+bρ{sub xx}{sup 2} and σ{sub AH}∝σ{sub xx}. Our study not only provide a strategy for further theoretical work on antiperovskite manganese nitrides but also shed promising light on utilizing their extrinsic AHE to fabricate spintronic devices.

  3. Magneto-optical spectroscopy of ferromagnetic shape-memory Ni-Mn-Ga alloy

    SciTech Connect (OSTI)

    Veis, M. Beran, L.; Zahradnik, M.; Antos, R.; Straka, L.; Kopecek, J.; Fekete, L.; Heczko, O.

    2014-05-07

    Magneto-optical properties of single crystal of Ni{sub 50.1}Mn{sub 28.4}Ga{sub 21.5} magnetic shape memory alloy in martensite and austenite phase were systematically studied. Crystal orientation was approximately along (100) planes of parent cubic austenite. At room temperature, the sample was in modulated 10M martensite phase and transformed to cubic austenite at 323?K. Spectral dependence of polar magneto-optical Kerr effect was obtained by generalized magneto-optical ellipsometry with rotating analyzer in the photon energy range from 1.2 to 4?eV, and from room temperature to temperature above the Curie point. The Kerr rotation spectra exhibit prominent features typical for complexes containing Mn atoms. Significant spectral changes during transformation to austenite can be explained by different optical properties caused by changes in density of states near the Fermi energy.

  4. Low temperature magnetic properties of magnesium substituted YbMnO{sub 3}

    SciTech Connect (OSTI)

    Sattibabu, Bhumireddi Bhatnagar, Anil K. Mohan, Dasari Das, Dibakar Sundararaman, Mahadevan; Siruguri, Vasudeva; Rayaprol, Sudhindra

    2014-04-24

    Structural and magnetic properties of polycrystalline Yb{sub 1−x}Mg{sub x}MnO{sub 3} (x = 0, 0.05 and 0.10) hexagonal compounds prepared by solid state method, have been studied. The structural analyses of the samples were carried out by Rietveld analysis of neutron diffraction data. With increasing Mg content, we find that the lattice parameter a decreases and c increases whereas the overall Mn-O bond length decreases. Magnetization measured as a function of magnetic field at 2.5 K exhibits hysteresis, which is attributed to ferromagnetic like ordering of Yb{sup 3+} sublattice. Temperature dependence of ac magnetic susceptibility, χ{sub ac}(T), shows no signature of spin-glass behavior. χ”(T) exhibits a sudden increase at low temperatures which is due to ordering of Yb{sup 3+} sublattice.

  5. Structural, elastic, electronic, magnetic and vibrational properties of CuCoMnGa under pressure

    SciTech Connect (OSTI)

    İyigör, Ahmet; Uğur, Şule

    2014-10-06

    First principles calculations for the structural, electronic, elastic and phonon properties of the cubic quaternary heusler alloy CuCoMnGa on pressure have been reported by density functional theory (DFT) within generalized gradient approximation (GGA). The calculated values of the elastic constants were used for estimations of the Debye temperatures, the bulk modulus, the shear modulus, the young modulus E, the poisson's ratio σ and the B/G ratio. The elastic constants satisfy all of the mechanical stability criteria. The electronic structures of the ferromagnetic configuration for CuCoMnGa have a metallic character. The estimated magnetic moment per formula unit is 3.76 μ{sub B}. The phonon dispersion is studied using the supercell approach, and the stable nature at 0.2 GPa pressure is observed.

  6. Homogeneity testing and quantitative analysis of manganese (Mn) in vitrified Mn-doped glasses by laser-induced breakdown spectroscopy (LIBS)

    SciTech Connect (OSTI)

    Unnikrishnan, V. K.; Nayak, Rajesh; Kartha, V. B.; Santhosh, C. E-mail: unnikrishnan.vk@manipal.edu; Sonavane, M. S.; Yeotikar, R. G.; Shah, M. L.; Gupta, G. P.; Suri, B. M.

    2014-09-15

    Laser-induced breakdown spectroscopy (LIBS), an atomic emission spectroscopy method, has rapidly grown as one of the best elemental analysis techniques over the past two decades. Homogeneity testing and quantitative analysis of manganese (Mn) in manganese-doped glasses have been carried out using an optimized LIBS system employing a nanosecond ultraviolet Nd:YAG laser as the source of excitation. The glass samples have been prepared using conventional vitrification methods. The laser pulse irradiance on the surface of the glass samples placed in air at atmospheric pressure was about 1.710{sup 9} W/cm{sup 2}. The spatially integrated plasma emission was collected and imaged on to the spectrograph slit using an optical-fiber-based collection system. Homogeneity was checked by recording LIBS spectra from different sites on the sample surface and analyzing the elemental emission intensities for concentration determination. Validation of the observed LIBS results was done by comparison with scanning electron microscope- energy dispersive X-ray spectroscopy (SEM-EDX) surface elemental mapping. The analytical performance of the LIBS system has been evaluated through the correlation of the LIBS determined concentrations of Mn with its certified values. The results are found to be in very good agreement with the certified concentrations.

  7. MN Lup: X-RAYS FROM A WEAKLY ACCRETING T TAURI STAR

    SciTech Connect (OSTI)

    Guenther, H. M.; Wolk, S. J.; Wolter, U.; Robrade, J.

    2013-07-01

    Young T Tauri stars (TTS) are surrounded by an accretion disk, which over time disperses due to photoevaporation, accretion, and possibly planet formation. The accretion shock on the central star produces an UV/optical veiling continuum, line emission, and X-ray signatures. As the accretion rate decreases, the impact on the central star must change. In this article we study MN Lup, a young star where no indications of a disk are seen in IR observations. We present XMM-Newton and VLT/UVES observations, some of them taken simultaneously. The X-ray data show that MN Lup is an active star with L{sub X} /L{sub bol} close to the saturation limit. However, we find high densities (n{sub e} > 3 Multiplication-Sign 10{sup 10} cm{sup -3}) in the X-ray grating spectrum. This can be well fitted using an accretion shock model with an accretion rate of 2 Multiplication-Sign 10{sup -11} M{sub Sun} yr{sup -1}. Despite the simple H{alpha} line profile which has a broad component, but no absorption signatures as typically seen on accreting TTS, we find rotational modulation in Ca II K and in photospheric absorption lines. These line profile modulations do not clearly indicate the presence of a localized hot accretion spot on the star. In the H{alpha} line we see a prominence in absorption about 2R{sub *} above the stellar surface-the first of its kind on a TTS. MN Lup is also the only TTS where accretion is seen, but no dust disk is detected that could fuel it. We suggest that MN Lup presents a unique and short-lived state in the disk evolution. It may have lost its dust disk only recently and is now accreting the remaining gas at a very low rate.

  8. Magnetic fields and fluctuations in weakly Mn doped ZnGeP{sub 2}

    SciTech Connect (OSTI)

    Mengyan, P. W.; Lichti, R. L.; Baker, B. B.; Celebi, Y. G.; Catak, E.; Carroll, B. R.; Zawilski, K. T.; Schunemann, P. G.

    2014-02-21

    We report on our measurements of local and bulk magnetic features in weakly Mn doped ZnGeP{sub 2}. Utilizing muon spin rotation and relaxation measurements, we identify local ferromagnetic order and fluctuations in the local fields as sampled by an implanted muon (?{sup +}). We also report on field induced ferromagnetism occurring above the claimed paramagnetic to ferromagnetic transition temperature (T{sub c} = 312 K)

  9. Inverse Design of Mn-based ternary p-type wide-gap oxides

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    used theory to predict band structure and transport properties for the d 5 transition metal (TM) oxides MnO and Fe 2 O 3 . Significance and Impact This work identified design principles for improving d 5 oxides as a new class of semiconductors with potential applications in energy conversion. Design Principles Demonstrated for Semiconducting d 5 Transition-Metal Oxides with Photovoltaic Applications Potential H. Peng and S. Lany, Phys. Rev. B (Rapid Comm.) 85, 201202(R) (2012). Figure 1:

  10. Thermoelectric study of crossroads material MnTe via sulfur doping

    SciTech Connect (OSTI)

    Xie, Wenjie Populoh, Sascha; Sagarna, Leyre; Trottmann, Matthias; Ga??zka, Krzysztof; Xiao, Xingxing; Liu, Yufei; He, Jian; Weidenkaff, Anke

    2014-03-14

    Here, we report thermoelectric study of crossroads material MnTe via iso-electronic doping S on the Te-site. MnTe{sub 1-x}S{sub x} samples with nominal S content of x?=?0.00, 0.05, and 0.10 were prepared using a melt-quench method followed by pulverization and spark plasma sintering. The X-ray powder diffraction, scanning electron microscopy, and ZAF-corrected compositional analysis confirmed that S uniformly substitutes Te up to slightly over 2%. A higher content of S in the starting materials led to the formation of secondary phases. The thermoelectric properties of MnTe{sub 1-x}S{sub x} samples were characterized by means of Seebeck coefficient, electrical conductivity, and thermal conductivity measurements from 300?K to 773?K. Furthermore, Hall coefficient measurements and a single parabolic band model were used to help gain insights on the effects of S-doping on the scattering mechanism and the carrier effective mass. As expected, S doping not only introduced hole charge carriers but also created short-range defects that effectively scatter heat-carrying phonons at elevated temperatures. On the other hand, we found that S doping degraded the effective mass. As a result, the ZT of MnTe{sub 0.9}S{sub 0.1} was substantially enhanced over the pristine sample near 400?K, while the improvement of ZT became marginal at elevated temperatures. A ZT???0.65 at 773?K was obtained in all three samples.

  11. Redox Active Layer-by-Layer Structures containing MnO2 Nanoparticles

    SciTech Connect (OSTI)

    Bazito, Fernanda; O'Brien, Robert; Buttry, Daniel A.

    2005-02-01

    Nanoscale materials provide unique properties that will enable new technologies and enhance older ones. One area of intense activity in which nanoscale materials are being used is in the development of new functional materials for battery applications. This effort promises superior materials with properties that circumvent many of the problems associated with traditional battery materials. Previously we have worked on several approaches for using nanoscale materials for application as cathode materials in rechargeable Li batteries. Our recent work has focused on synthesizing MnO2 nanoparticles and using these in layer-by-layer (LbL) structures to probe the redox properties of the nanoparticles. We show that the aqueous colloidal nanoparticles produced by butanol reduction of tetramethylammonium permanganate can be trapped in thin films using a layer-by-layer deposition approach, and that these films are both redox active and exhibit kinetically facile electrochemical responses. We show cyclic voltammetry of MnO2 colloidal nanoparticles entrapped in a LbL thin film at an ITO electrode surface using poly(diallyldimethylammonium chloride) (PDDA). CV experiments demonstrate that Li+ insertion accompanies Mn(IV) reduction in LiClO4 supporting electrolytes, and that reduction is hindered in supporting electrolytes containing only tetrabutylammonium cations. We also show that electron propagation through multilayer films is facile, suggesting that electrons percolate through the films via electron exchange between nanoparticles.

  12. Magnetization dynamics and frustration in the multiferroic double perovskite Lu2MnCoO6

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zapf, Vivien S.; Ueland, B. G.; Laver, Mark; Lonsky, Martin; Pohlit, Merlin; Muller, Jens; Lancaster, Tom; Moller, Johannes S.; Blundell, Stephen J.; Singleton, John; et al

    2016-04-29

    Here, we investigate the magnetic ordering and the magnetization dynamics (from kHz to THz time scales) of the double perovskite Lu2MnCoO6 using elastic neutron diffraction, muon spin relaxation, and micro-Hall magnetization measurements. This compound is known to be a type II multiferroic with the interesting feature that a ferromagneticlike magnetization hysteresis loop couples to an equally hysteretic electric polarization in the bulk of the material despite a zero-field magnetic ordering of the type ↑↑↓↓ along Co-Mn spin chains. Here we explore the unusual dynamics of this compound and find extremely strong fluctuations, consistent with the axial next-nearest-neighbor Ising (ANNNI) modelmore » for frustrated spin chains. We identify three temperature scales in Lu2MnCoO6 corresponding to the onset of highly fluctuating long-range order below TN = 50±3 K identified from neutron scattering, the onset of magnetic and electric hysteresis, with change in kHz magnetic and electric dynamics below a 30 K temperature scale, and partial freezing of ~MHz spin fluctuations in the muon spin relaxation data below 12 ± 3 K. Our results provide a framework for understanding the multiferroic behavior of this compound and its hysteresis and dynamics.« less

  13. Magnetization-steps in Y?CoMnO? double perovskite: The role of antisite disorder

    SciTech Connect (OSTI)

    Nair, Harikrishnan S. Xiao, Yinguo; Brckel, Th.; Cherian, Dona; Elizabeth, Suja; Hansen, Thomas; Chatterji, Tapan

    2014-09-28

    Antisite disorder is observed to have significant impact on the magnetic properties of the double perovskite YCoMnO? which has been recently identified as a multiferroic. A paramagnetic-ferromagnetic phase transition occurs in this material at Tc ? 75 K. At 2 K, it displays a strong ferromagnetic hysteresis with a significant coercive field of Hc ? 15 kOe. Sharp steps are observed in the hysteresis curves recorded below 8 K. In the temperature range 2 K ? T ? 5 K, the hysteresis loops are anomalous as the virgin curve lies outside the main loop. The field-cooling conditions as well as the rate of field-sweep are found to influence the steps. Quantitative analysis of the neutron diffraction data shows that at room temperature, Y?CoMnO? consists of 62% of monoclinic P2?/n with nearly 70% antisite disorder and 38% Pnma. The bond valence sums indicate the presence of other valence states for Co and Mn which arise from disorder. We explain the origin of steps by using a model for pinning of magnetization at the antiphase boundaries created by antisite disorder. The steps in magnetization closely resemble the martensitic transformations found in intermetallics and display first-order characteristics as revealed in the Arrott's plots.

  14. MnO{sub 2}@colloid carbon spheres nanocomposites with tunable interior architecture for supercapacitors

    SciTech Connect (OSTI)

    Zhang, Yuxin; Liu, Chuanpu; Wen, Zhongquan

    2014-01-01

    Graphical abstract: - Highlights: MnO{sub 2}@CSs nanocomposites have been successfully synthesized in room temperature. The composites exhibited three structures: coreshell, yolkshell and hollow structure. The yolkshell structure exhibited a high specific capacitance and cycling stability. - Abstract: MnO{sub 2}@colloid carbon spheres nanocomposites with tunable interior architecture have been synthesized by a facile and cost-effective strategy at room temperature. The structure and morphology of as-prepared nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption, focused ion beam scanning electron microscopy (FIB/SEM) and high-resolution transmission electron microscopy (HRTEM). The as-obtained composites exhibited a three-dimensional architecture with coreshell, yolkshell and hollow interior structure. Furthermore, the electrochemical properties of composites were evaluated by cycle voltammetric (CV) and galvanostatic chargedischarge measurements. The yolkshell structure exhibited the optimized pseudocapacitance performance, revealing a specific capacitance (273 F g{sup ?1}) with a good rate and cycling stability, owing to its unique structure and the poor crystallinity of MnO{sub 2} nanofilms. Therefore, this facile synthetic strategy could be useful to design and synthesis of tunable nanostructures with enhanced supercapacitor behavior.

  15. Magnetoelectric coupling tuned by competing anisotropies in Mn1−xNixTiO3

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Chi, Songxue; Ye, Feng; Zhou, H. D.; Choi, E. S.; Hwang, J.; Cao, Huibo; Fernandez-Baca, Jaime A.

    2014-10-24

    A flop of electric polarization from Pmore » $$\\|$$c (Pc) to P$$\\|$$ a (Pa) is observed in MnTiO3 as a spin flop transtion is triggered by a c-axis magnetic field, H$$\\|$$c=7 T. The critical magnetic field for Pa is significantly reduced in Mn1-xNixTiO3 (x=0.33). Neutron diffraction measurements revealed similar magnetic arrangements for the two compositions where the ordered spins couple antiferromagnetically with their nearest intra- and inter-planar neighbors. In the x=0.33 system, the single ion anisotropies of Mn2+ and Ni2+ compete and give rise to an additional spin reorientation transition at TR. A magnetic field, Hc, aligns the spins along c for TRN. The rotation of the collinear spins away from the c-axis for TR alters the magnetic point symmetry and gives rise to new ME susceptibility tensor form. Such linear ME response provides satisfactory explanation for behavior of field-induced electric polarization in both compositions. As the Ni content increases to x=0.5 and 0.68, the ME effect disappears as a new magnetic phase emerges.« less

  16. Spin-phonon study of EuMn{sub 2}O{sub 5} nanorods

    SciTech Connect (OSTI)

    Hsu, Ting-Wei; Yang, Chung-Cheun Tong, Yong-Xiang; Shih, Wei-Jhe; Lin, Kuen-Song

    2015-05-07

    EuMn{sub 2}O{sub 5} multiferroic nanorods, with diameters radial × (〈L{sub C}〉) lengths of 25(6) nm × 47(15) nm and 51(16) nm × 70(26) nm, were fabricated by the hydrothermal method. Ferrimagnetic ordering below 50 K (T*) is observed in the 〈L{sub C}〉 = 70 nm sample, which exhibited ferromagnetic (FM) behavior below T* in a field cooling process. No similar behavior was found in the 〈L{sub C}〉 = 47 nm sample. These observations reveal that only the 〈L{sub C}〉 = 70 nm sample has a meta-FM state, and this sample exhibits the stronger coupling between the Mn ions. Raman spectra of both sets of samples were obtained in 0, 610, 1000, 1600, and 2000 G magnetic fields. The red-shift of the A{sub g} (681 cm{sup −1}) mode of the both samples increased with the strength of the field above 1000 G, indicating the existence of spin-phonon interaction. The smaller sampled exhibited a larger red-shift, suggesting that the size importantly affects the of EuMn{sub 2}O{sub 5} nanorods.

  17. Antiferromagnetic dipolar ordering in [Co{sub 2}MnGe/V]{sub N} multilayers

    SciTech Connect (OSTI)

    Bergmann, A.; Grabis, J.; Zabel, H.; Westerholt, K.; Toperverg, B.P.; Leiner, V.; Wolff, M.

    2005-12-01

    We have studied [Co{sub 2}MnGe/V]{sub N} multilayers with a thickness of the V layers t{sub V} between 1.5 and 10 nm and a fixed thickness of the Heusler layer t{sub Co{sub 2}}{sub MnGe}=3 nm by x-ray scattering, neutron reflectivity, and magnetization measurements. In the thickness range t{sub V}{<=}3 nm neutron reflectivity results provide clear evidence for an antiferromagnetic (af) interlayer long-range order below a Neel temperature T{sub N}. The interlayer long range order does not show an oscillating character and is stabilized by a weak af coupling field H{sub af}{approx_equal}100 Oe. We attribute the af coupling to magnetic dipolar stray fields originating from magnetically rough surfaces of a granular Co{sub 2}MnGe microstructure. In the thickness range t{sub V}{>=}4 nm the multilayers undergo a cluster glass transition at T{sub f}{approx_equal}150 K. At high temperatures above T{sub N} or T{sub f} the mutilayers are superparamagnetic with a huge cluster magnetic moment {mu}{sub c}{>=}10{sup 5}{mu}{sub B}.

  18. Mesoporous MnCeOx solid solutions for low temperature and selective oxidation of hydrocarbons

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zhang, Pengfei; Lu, Hanfeng; Zhou, Ying; Zhang, Li; Wu, Zili; Yang, Shize; Shi, Hongliang; Zhu, Qiulian; Chen, Yinfei; Dai, Sheng

    2015-10-15

    The development of noble-metal-free heterogeneous catalysts that can realize the aerobic oxidation of C–H bonds at low temperature is a profound challenge in the catalysis community. Here we report the synthesis of a mesoporous Mn0.5Ce0.5Ox solid solution that is highly active for the selective oxidation of hydrocarbons under mild conditions (100–120 °C). Notably, the catalytic performance achieved in the oxidation of cyclohexane to cyclohexanone/cyclohexanol (100 °C, conversion: 17.7%) is superior to those by the state-of-art commercial catalysts (140–160 °C, conversion: 3-5%). Finally, the high activity can be attributed to the formation of a Mn0.5Ce0.5Ox solid solution with an ultrahigh manganesemore » doping concentration in the CeO2 cubic fluorite lattice, leading to maximum active surface oxygens for the activation of C–H bonds and highly reducible Mn4+ ions for the rapid migration of oxygen vacancies from the bulk to the surface.« less

  19. Kinetics of MN based sorbents for hot coal gas. Quarterly report, September--December 1996

    SciTech Connect (OSTI)

    1996-12-31

    Manganese-based sorbents have been investigated for the removal of hydrogen sulfide (the primary sulfur bearing compound) from hot coal gases prior to its use in combined cycle turbines. Four formulations of Mn-based sorbents were tested in an ambient-pressure fixed-bed reactor to determine steady state H{sub 2}S concentrations, breakthrough times and effectiveness of the sorbent when subjected to cyclic sulfidation and regeneration testing. In a previous report, the sulfidation results were presented. Manganese-based sorbents with molar ratios > 1:1 Mn:Substrate were effective in reducing the H{sub 2}S concentration in simulated coal gases to less than 100 ppmv over five cycles. Actual breakthrough time for formulation C6-2-1100 was as high as 73% of breakthrough time based on wt% Mn in sorbent. In this report, the regeneration results will be presented. Regeneration tests determined that loaded pellets can be fully regenerated in air/steam mixture at 750{degrees}C with minimal sulfate formation. 16 refs., 9 figs., 5 tabs.

  20. Incommensurate crystal supercell and polarization flop observed in the magnetoelectric ilmenite MnTiO3

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Silverstein, Harlyn J.; Skoropata, Elizabeth; Sarte, Paul M.; Mauws, Cole; Aczel, Adam A.; Choi, Eun Sang; van Lierop, Johan; Wiebe, Christopher R.; Zhou, Haidong

    2016-02-19

    In the last few years the magnetoelectric behavior of MnTiO3 has been observed even though its been studied for many decades. We use neutron scattering on two separately grown single crystals and two powder samples to show the presence of a supercell that breaks R (3) over bar symmetry. We also present the temperature and field dependence of the dielectric constant and pyroelectric current and show evidence of nonzero off-diagonal magnetoelectric tensor elements (forbidden by R (3) over bar symmetry) followed by a polarization flop accompanying the spin flop transition at mu H-0(SF) = 6.5T. Mossbauer spectroscopy on MnTiO3 gentlymore » doped with Fe-57 was used to help shed light on the impact of the supercell on the observed behavior. Moreover, the full supercell structure could not be solved at this time due to a lack of visible reflections, the full scope of the results presented here suggest that the role of local spin-lattice coupling in the magnetoelectric properties of MnTiO3 is likely more important than previously thought.« less

  1. Correlating Local Structure with Electrochemical Activity in Li2MnO3

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Nanda, Jagjit; Sacci, Robert L.; Veith, Gabriel M.; Dixit, Hemant M.; Cooper, Valentino R.; Pezeshki, Alan M.; Ruther, Rose E.

    2015-07-31

    Li2MnO3 is of interest as one component of the composite lithium-rich oxides, which are under development for high capacity, high voltage cathodes in lithium ion batteries. Despite such practical importance, the mechanism of electrochemical activity in Li2MnO3 is contested in the literature, as are the effects of long-term electrochemical cycling. Here, Raman spectroscopy and mapping are used to follow the chemical and structural changes that occur in Li2MnO3. Both conventional slurry electrodes and thin films are studied as a function of the state of charge (voltage) and cycle number. Thin films have similar electrochemical properties as electrodes prepared from slurries,more » but allow for spectroscopic investigations on uniform samples without carbon additives. Spectral changes correlate well with electrochemical activity and support a mechanism whereby capacity is lost upon extended cycling due to the formation of new manganese oxide phases. Raman mapping of both thin film and slurry electrodes charged to different voltages reveals significant variation in the local structure. Poor conductivity and slow kinetics associated with a two-phase reaction mechanism contribute to the heterogeneity.« less

  2. Preparation and characterization of nanostructured NiO/MnO{sub 2} composite electrode for electrochemical supercapacitors

    SciTech Connect (OSTI)

    Liu Enhui Li Wen; Li Jian; Meng Xiangyun; Ding Rui; Tan Songting

    2009-05-06

    Nanostructured nickel-manganese oxides composite was prepared by the sol-gel and the chemistry deposition combination new route. The surface morphology and structure of the composite were characterized by scanning electron microscope and X-ray diffraction. The as-synthesized NiO/MnO{sub 2} samples exhibit higher surface area of 130-190 m{sup 2} g{sup -1}. Cyclic voltammetry and galvanostatic charge/discharge measurements were applied to investigate the electrochemical performance of the composite electrodes with different ratios of NiO/MnO{sub 2}. When the mass ratio of MnO{sub 2} and NiO in composite material is 80:20, the specific capacitance value of NiO/MnO{sub 2} calculated from the cyclic voltammetry curves is 453 F g{sup -1}, for pure NiO and MnO{sub 2} are 209, 330 F g{sup -1} in 6 mol L{sup -1} KOH electrolyte and at scan rate of 10 mV s{sup -1}, respectively. The specific capacitance of NiO/MnO{sub 2} electrode is much larger than that of each pristine component. Moreover, the composite electrodes showed high power density and stable electrochemical properties.

  3. The structure of the Caenorhabditis elegans manganese superoxide dismutase MnSOD-3-azide complex

    SciTech Connect (OSTI)

    Hunter, Gary J.; Trinh, Chi H.; Bonetta, Rosalin; Stewart, Emma E.; Cabelli, Diane E.; Hunter, Therese

    2015-08-27

    C. elegans MnSOD-3 has been implicated in the longevity pathway and its mechanism of catalysis is relevant to the aging process and carcinogenesis. The structures of MnSOD-3 provide unique crystallographic evidence of a dynamic region of the tetrameric interface (residues 41–54). We have determined the structure of the MnSOD-3-azide complex to 1.77-Å resolution. The analysis of this complex shows that the substrate analog, azide, binds end-on to the manganese center as a sixth ligand and that it ligates directly to a third and new solvent molecule also positioned within interacting distance to the His30 and Tyr34 residues of the substrate access funnel. This is the first structure of a eukaryotic MnSOD-azide complex that demonstrates the extended, uninterrupted hydrogen-bonded network that forms a proton relay incorporating three outer sphere solvent molecules, the substrate analog, the gateway residues, Gln142, and the solvent ligand. This configuration supports the formation and release of the hydrogen peroxide product in agreement with the 5-6-5 catalytic mechanism for MnSOD. The high product dissociation constant k₄ of MnSOD-3 reflects low product inhibition making this enzyme efficient even at high levels of superoxide.

  4. A XANES and EXAFS Study of Hydration and Ion Pairing in Ambient Aqueous MnBr[subscript 2] Solutions

    SciTech Connect (OSTI)

    Chen, Yongsheng; Fulton, John L.; Partenheimer, Walter

    2008-09-25

    Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopies were used to probe the first-shell coordination structure of Mn(II) in aqueous MnBr{sub 2} solutions at ambient conditions from very dilute to the near saturation limit. The Mn K-edge EXAFS spectra for 0.05 and 0.2 m solutions showed that there was no Br(-I) in the first shell, and that the Mn(II) was fully hydrated with six water molecules in an octahedral arrangement. In contrast, for 6 m solution, the coordination number of water was reduced to about 5, and an average of about one bromine atom was present in the first shell as a contact ion pair. The 1s {yields} 4p transition at 6545.5 eV confirmed the observation of Mn-Br contact ion pairs at high concentrations and the 1s {yields} 3d transition at 6539.5 eV showed that the first shell coordination symmetry remained octahedral even in the presence of Mn-Br ion pairs.

  5. Role of the antiferromagnetic pinning layer on spin wave properties in IrMn/NiFe based spin-valves

    SciTech Connect (OSTI)

    Gubbiotti, G. Tacchi, S.; Del Bianco, L.; Bonfiglioli, E.; Giovannini, L.; Spizzo, F.; Zivieri, R.; Tamisari, M.

    2015-05-07

    Brillouin light scattering (BLS) was exploited to study the spin wave properties of spin-valve (SV) type samples basically consisting of two 5 nm-thick NiFe layers (separated by a Cu spacer of 5 nm), differently biased through the interface exchange coupling with an antiferromagnetic IrMn layer. Three samples were investigated: a reference SV sample, without IrMn (reference); one sample with an IrMn underlayer (10 nm thick) coupled to the bottom NiFe film; one sample with IrMn underlayer and overlayer of different thickness (10 nm and 6 nm), coupled to the bottom and top NiFe film, respectively. The exchange coupling with the IrMn, causing the insurgence of the exchange bias effect, allowed the relative orientation of the NiFe magnetization vectors to be controlled by an external magnetic field, as assessed through hysteresis loop measurements by magneto-optic magnetometry. Thus, BLS spectra were acquired by sweeping the magnetic field so as to encompass both the parallel and antiparallel alignment of the NiFe layers. The BLS results, well reproduced by the presented theoretical model, clearly revealed the combined effects on the spin dynamic properties of the dipolar interaction between the two NiFe films and of the interface IrMn/NiFe exchange coupling.

  6. Structure of the c(2x2) Mn/Ni(001) surface alloy by quantitative photoelectron diffraction

    SciTech Connect (OSTI)

    Banerjee, S.; Denlinger, J.; Chen, X.

    1997-04-01

    Surface alloys are two-dimensional metallic systems that can have structures that are unique to the surface, and have no counterpart in the bulk binary phase diagram. A very unusual structure was reported for the Mn-Ni system, based on a quantitative LEED structure determination, which showed that the Mn atoms were displaced out of the surface by a substantial amount. This displacement was attributed to a large magnetic moment on the Mn atoms. The structure of the Mn-Ni surface alloy was proposed to be based on a bulk termination model. Magnetic measurements on the Mn-Ni surface alloys, however, showed conclusively that the magnetic structure of these surface alloys is completely different from the bulk alloy analogs. For example, bulk MnNi is an antiferromagnet, whereas the surface alloy is ferromagnetic. This suggests that the proposed structure based on bulk termination, may not be correct. X-ray Photoelectron Diffraction (XPD) techniques were used to investigate this structure, using both a comparison to multiple scattering calculations and photoelectron holography. In this article the authors present some of the results from the quantitative analysis of individual diffraction patterns by comparison to theory.

  7. Why MnIn{sub 2}O{sub 4} spinel is not a transparent conducting oxide?

    SciTech Connect (OSTI)

    Martinez-Lope, M.J.; Retuerto, M.; Calle, C. de la; Porcher, Florence

    2012-03-15

    The title compound has been synthesized by a citrate technique. The crystal structure has been investigated at room temperature from high-resolution neutron powder diffraction (NPD) data. It crystallizes in a cubic spinel structure, space group Fd3-bar m, Z=8, with a=9.0008(1) A at 295 K. It exhibits a crystallographic formula (Mn{sub 0.924(2)}In{sub 0.076(2)}){sub 8a}(In{sub 1.804(2)}Mn{sub 0.196(2)}){sub 16d}O{sub 4}, where 8a and 16d stand for the tetrahedral and octahedral sites of the spinel structure, respectively, with a slight degree of inversion, {lambda}=0.08. MnIn{sub 2}O{sub 4} shows antiferromagnetic interactions below T{sub N} Almost-Equal-To 40 K, due to the statistical distribution of Mn ions over the two available sites. Unlike the related MgIn{sub 2}O{sub 4} and CdIn{sub 2}O{sub 4} spinels, well known as transparent conducting oxides, MnIn{sub 2}O{sub 4} is not transparent and shows a poor conductivity ({sigma}=0.38 S cm{sup -1} at 1123 K): the presence of Mn ions, able to adopt mixed valence states, localizes the charges that, otherwise, would be delocalized in the spinel conduction band. - Graphical Abstract: From NPD data the crystallographic formula (Mn{sub 0.924(2)}In{sub 0.076(2)}){sub 8a}(In{sub 1.804(2)}Mn{sub 0.196(2)}){sub 16d}O{sub 4}, shows a slight degree of inversion, {lambda}=0.08 and a certain In deficiency. The presence of Mn ions, able to adopt mixed oxidation states, localize the charges that, otherwise, would be delocalized in the spinel conduction band; the presence of localized Mn{sup 2+} and Mn{sup 3+} ions provides the characteristic brown color. Highlights: Black-Right-Pointing-Pointer Accurate structural determination from NPD data: inversion degree (8%), and In deficiency. Black-Right-Pointing-Pointer Bond-valence indicates Mn{sup 2+}-Mn{sup 3+} ions; edge-sharing octahedra contain 90% In{sup 3+}+10% Mn{sup 3+} cations. Black-Right-Pointing-Pointer Conductivity several orders of magnitude lower than those of MgIn{sub 2}O

  8. m/sup +/SR studies on pure MnF/sub 2/ and site-diluted (Mn/sub 0. 5/Zn/sub 0. 5/)F/sub 2/

    SciTech Connect (OSTI)

    Uemura, Y.J.; Keitel, R.; Senba, M.; Kiefl, R.F.; Kreitzman, S.R.; Noakes, D.R.; Brewer, J.H.; Harshman, D.R.; Ansaldo, E.J.; Crowe, K.M.

    1986-01-01

    Positive muon spin rotation and relaxation measurements have been carried out on the antiferromagnets, pure MnF/sub 2/ and site-diluted (Mn/sub 0.5/Zn/sub 0.5/)F/sub 2/, above and below the Neel temperature T/sub N/ using single-crystal specimens. Two different muon signals have been found in the pure MnF/sub 2/; with the precession frequency nu/sub A/ = 1.3 GHz for the site A and nu/sub B/ = 152 MHz for the site B measured in zero external magnetic field at T = 5 K. We propose a picture that the signal from the A site represents the ''muonium'' state, and discuss the characteristic features of muonium in magnetic materials. The spin relaxation rate 1/T/sub 1/, measured in zero external field, decreases rapidly with decreasing temperature below T/sub N/. The mechanism of the spin relaxation above T/sub N/ is explained by the exchange fluctuations of the Mn moments, while below T/sub N/ by the Raman scattering of spin waves. At the same normalized temperature T/T/sub N/, 1/T/sub 1/ observed in the diluted (Mn/sub 0.5/Zn/sub 0.5/)F/sub 2/ is significantly larger than that in the pure MnF/sub 2/ below T/sub N/. The difference between the pure and diluted systems is related to the large spectral weight of low-energy magnons in (Mn/sub 0.5/Zn/sub 0.5/)F/sub 2/ found by neutron scattering.

  9. Effect of organic solvents on particle size of Mn{sub 3}O{sub 4} nanoparticles synthesized by a solvothermal method

    SciTech Connect (OSTI)

    Song, Rui; Feng, Shouhua; Wang, Hongjun; Hou, Changmin

    2013-06-15

    In this paper, a modified simple solvothermal method is employed to synthesize Mn{sub 3}O{sub 4} nanocrystals using four different solvents: acetone, ethanol, N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO). Mn{sub 3}O{sub 4} nanoparticles with a tetragonal hausmannite nano-structure are characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), as well as superconducting quantum interference device magnetometer (SQUID). The Mn{sub 3}O{sub 4} particle size is found to have a strong dependency on the solvent used. A reaction scheme is proposed to understand this dependency, suggesting that the solvent coordinating capability has a critical effect on Mn{sub 3}O{sub 4} particle size. The stronger the coordinating capability of the solvent is, the smaller the Mn{sub 3}O{sub 4} particle size is. In addition, magnetic properties of the nano-structured Mn{sub 3}O{sub 4} are also tested and discussed. - Graphical abstract: The comparison of the particle size of Mn{sub 3}O{sub 4} nanoparticles synthesized using different solvents and HRTEM image of Mn{sub 3}O{sub 4} individual nanoparticle revealed its single-crystal nature. - Highlights: • Mn{sub 3}O{sub 4} nanocrystals were synthesized using different solvents by a solvothermal method. • The particle size of Mn{sub 3}O{sub 4} nanocrystal is found to have a strong dependency on the solvent used. • A reaction mechanism is proposed to explain the difference of particle size of Mn{sub 3}O{sub 4} nanocrystals. • Magnetic properties of Mn{sub 3}O{sub 4} nanocrystals with different particle size are tested and compared.

  10. Structure and magnetic properties of Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15}, a new 10H-polytype in the Ba-Ce-Mn-O system

    SciTech Connect (OSTI)

    Macias, Mario A.; Mentre, Olivier; Cuello, Gabriel J.; Gauthier, Gilles H.

    2013-02-15

    Based on the peculiar magnetic properties that are observed in pseudo one-dimensional manganites, we decided to synthesize the new Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15} compound. The preparation was performed by solid state reaction in air at about 1350 Degree-Sign C, for which we found that the compound crystallizes in a hexagonal symmetry with space group P6{sub 3}/mmc (No-194) and cell parameters a=b=5.7861(2) A and c=23.902(1) A. The structural description was correlated with neutron diffraction and bond valence calculations, confirming the presence of Ce{sup 4+} and Mn{sup 4+} segregated in the different crystallographic positions. Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15} displays evidence for strong AFM couplings already set at room temperature. The main arrangement of Mn{sup 4+} in magnetically isolated tetramers of face-sharing octahedra is responsible for a metamagnetic-like transition around 50 K. - Graphical abstract: The new Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15} polytype shows strong AFM couplings in magnetically isolated [Ce{sub 0.25}Mn{sub 3.75}O{sub 15}] tetramers of face-sharing octahedral, resulting in a metamagnetic-like transition around 50 K. Highlights: Black-Right-Pointing-Pointer Ba{sub 5}Ce{sub 1.25}Mn{sub 3.75}O{sub 15}, a new 10H polytype, has been prepared in the Ba-Ce-Mn-O system. Black-Right-Pointing-Pointer The compound crystallizes in the P6{sub 3}/mmc space group with (cchhh){sub 2} stacking sequence. Black-Right-Pointing-Pointer [Ce{sub 0.25}Mn{sub 3.75}O{sub 15}] tetramers are separated by [CeO{sub 6}] octahedra in the structure. Black-Right-Pointing-Pointer Instead of robust AFM ordering, a metamagnetic-like transition is found around 50 K.

  11. In situ and ex situ spectroelectrochemical and X-ray absorption studies on rechargeable, chemically-modified and other MnO{sub 2} materials

    SciTech Connect (OSTI)

    Conway, B.E.; Qu, D.; McBreen, J. |

    1992-12-31

    A combined series of in situ and ex situ UV spectroelectrochemical and X-ray absorption studies have been made on MnO{sub 2}, chemically-modified by small amounts of Bi(III), and comparatively on other MnO{sub 2} materials such as a blank (Bi-free) and {gamma}-MnO{sub 2}. These procedures are applied in order to follow the oxidation-states of Bi and of Mn during the course of discharge and recharge of MnO{sub 2} as a battery cathode material, and the extents of rechargeability that can be achieved with such materials. Presence of Bi appears to provide a preferred ``heterogeneous`` discharge/recharge pathway involving a soluble Mn(III) intermediate, over the alternative ``electron-proton`` hopping, solid-state mechanism. From XAS results, it is concluded that presence of Bi, although not affecting the O-coordination, does influence the Mn-Mn coordination, determining the way the MnO{sub 2} coordination octahedra are connected.

  12. Mixed metallic Ba(Co,Mn)X{sub 0.2-x}O{sub 3-{delta}} (X=F, Cl) hexagonal perovskites

    SciTech Connect (OSTI)

    Iorgulescu, Mihaela; Roussel, Pascal; Tancret, Nathalie; Renaut, Nicolas; Tiercelin, Nicolas; Mentre, Olivier

    2013-02-15

    We show here that the incorporation of Mn in Ba-Co-oxohalide, BaCoX{sub 0.2-x}O{sub 3-{delta}}, hexagonal perovskite stabilizes the 6H-form (stacking sequence (chhhch Prime ); c, h=[BaO{sub 3}] and h Prime =[BaOX] layers), with tetramers of face-sharing octahedra) rather than the trimeric 10H-form. On the contrary to previous results on the Fe incorporation in similar system leading to more reduced 10H-compounds, the Mn effect is to increase the mean (Co/Mn) valence better suited to the 6H form. We experienced a poor Mn/Co miscibility during our syntheses leading to great difficulties to isolate mixed Co/Mn single phase materials and/or weak reproducibility. Powder neutron diffraction data shows a mixed Mn/Co octahedral occupancy, while the tetrahedra are filled by Co{sup 3+} cations. Anionic vacancies were refined in the h Prime -[BaO{sub 1-z}X{sub 1-x}] layer and the next c-[BaO{sub 3-z}] layers, while the h-[BaO{sub 3}] layers are not oxygen deficient. Magnetic properties suggest that a part of Mn cations remain paramagnetic until low temperature, while isolated spin clusters (probably driven by AFM Co tetrahedral dimers) behave as low-dimensional AFM systems. Transport measurements reveal a transition from high-temperature metallic to low-temperature semi-conducting states that could occur from defect shallow donor upon the Mn for Co substitution. - Graphical abstract: The incorporation of Mn in Ba-Co-oxohalide, BaCoX{sub 0.2-x}O{sub 3-{delta}}, hexagonal perovskite stabilizes the 6H-form with tetrameric (Co,Mn){sub 4}O{sub 15} face sharing linear chains. This results from a oxidizing Mn effect and particular Mn/Co distribution. Highlights: Black-Right-Pointing-Pointer The incorporation of Mn in BaCoX{sub 0.2-x}O{sub 3-{delta}} (X=F,Cl) hexagonal perovskites stabilizes the 6H-form. Black-Right-Pointing-Pointer It contains tetrameric (Co,Mn){sub 4}O{sub 15} face sharing linear chains. Black-Right-Pointing-Pointer The preference for such chains better than

  13. Probing The Electrode/Electrolyte Interface in The Lithium Excess Layered Oxide Li1.2Ni0.2Mn0.6O2

    SciTech Connect (OSTI)

    Carroll, Kyler J; Qian, Danna; Fell, Chris; Calvin, Scott; Veith, Gabriel M; Chi, Miaofang; Dudney, Nancy J; Meng, Ying Shirley

    2013-01-01

    A detailed surface investigation of the lithium-excess nickel manganese layered oxide Li1.2Ni0.2Mn0.6O2 structure was carried out using x-ray photoelectron spectroscopy (XPS), total electron yield and transmission x-ray absorption spectroscopy (XAS), and electron energy loss spectroscopy (EELS) during the first two electrochemical cycles. All spectroscopy techniques consistently showed the presence of Mn4+ in the pristine material and a surprising reduction of Mn at the voltage plateau during the first charge. The Mn reduction is accompanied by the oxygen loss revealed by EELS. Upon the first discharge, the Mn at the surface never fully returns back to Mn4+. The electrode/electrolyte interface of this compound consists of the reduced Mn at the crystalline defect-spinel inner layer and an oxidized Mn species simultaneously with the presence of a superoxide species in amorphous outer layer. This proposed model signifies that oxygen vacancy formation and lithium removal result in electrolyte decomposition and superoxide formation, leading to Mn activation/dissolution and surface layer-spinel phase transformation. The results also indicate that the role of oxygen is complex and significant in contributing to the extra capacity of this class of high energy density cathode materials.

  14. Effect of Mn doping on the structural, optical, and magnetic properties of In{sub 2}O{sub 3} films

    SciTech Connect (OSTI)

    Wang, Shiqi; An, Yukai; Duan, Lingshen; Liu, Huarui; Liu, Jiwen; Wu, Zhonghua

    2013-11-15

    (In{sub 1−x}Mn{sub x}){sub 2}O{sub 3} films were grown by radio frequency-magnetron sputtering technique. Effect of Mn doping on the structural, optical, and magnetic properties of films is investigated systematically. The detailed structure analyses suggest that Mn ions substitute for In{sup 3+} sites of the In{sub 2}O{sub 3} lattice in the valence of +2 states, and Mn-related secondary phases or clusters as the source of ferromagnetism is safely ruled out. All films show typical room temperature ferromagnetism. The saturation magnetization M{sub s} increases first, and then decreases, while carrier concentration n{sub c} decreases monotonically with Mn doping, implying that the ferromagnetism is not directly induced by the mediated carriers. The optical bandgap E{sub g} of films decreases monotonically with the increase of Mn concentration, and there exists a linear functional dependence between E{sub g} and n{sub c}{sup 2/3}, which is consistent with Burstein-Moss shift arguments. It can be concluded that the ferromagnetic order in Mn-doped In{sub 2}O{sub 3} films is intrinsic, arising from Mn atoms substitution for the In sites of In{sub 2}O{sub 3} lattice. The oxygen vacancies play a mediation role on the ferromagnetic couplings between the Mn ions.

  15. Robust antiferromagnetism preventing superconductivity in pressurized (Ba0.61K0.39)Mn2Bi2

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Gu, Dachun; Dai, Xia; Le, Congcong; Sun, Liling; Wu, Qi; Saparov, Bayrammurad; Guo, Jing; Gao, Peiwen; Zhang, Shan; Zhou, Yazhou; et al

    2014-12-05

    BaMn2Bi2 possesses an iso-structure of iron pnictide superconductors and similar antiferromagnetic (AFM) ground state to that of cuprates, therefore, it receives much more attention on its properties and is expected to be the parent compound of a new family of superconductors. When doped with potassium (K), BaMn2Bi2 undergoes a transition from an AFM insulator to an AFM metal. Consequently, it is of great interest to suppress the AFM order in the K-doped BaMn2Bi2 with the aim of exploring the potential superconductivity. Here, we report that external pressure up to 35.6 GPa cannot suppress the AFM order in the K-doped BaMn2Bi2more » to develop superconductivity in the temperature range of 300 K–1.5 K, but induces a tetragonal (T) to an orthorhombic (OR) phase transition at ~20 GPa. Theoretical calculations for the T and OR phases, on basis of our high-pressure XRD data, indicate that the AFM order is robust in the pressurized Ba0.61K0.39Mn2Bi2. Utlimately, both of our experimental and theoretical results suggest that the robust AFM order essentially prevents the emergence of superconductivity.« less

  16. Catalytic conversion of syngas to mixed alcohols over Zn-Mn promoted Cu-Fe based catalyst

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Lu, Yongwu; Yu, Fei; Hu, Jin; Liu, Jian

    2012-04-12

    Zn-Mn promoted Cu-Fe based catalyst was synthesized by the co-precipitation method. Mixed alcohols synthesis from syngas was studied in a half-inch tubular reactor system after the catalyst was reduced. Zn-Mn promoted Cu-Fe based catalyst was characterized by SEM-EDS, TEM, XRD, and XPS. The liquid phase products (alcohol phase and hydrocarbon phase) were analyzed by GC-MS and the gas phase products were analyzed by GC. The results showed that Zn-Mn promoted Cu-Fe based catalyst had high catalytic activity and high alcohol selectivity. The maximal CO conversion rate was 72%, and the yield of alcohol and hydrocarbons were also very high. Cumore » (111) was the active site for mixed alcohols synthesis, Fe2C (101) was the active site for olefin and paraffin synthesis. The reaction mechanism of mixed alcohols synthesis from syngas over Zn-Mn promoted Cu-Fe based catalyst was proposed. Here, Zn-Mn promoted Cu-Fe based catalyst can be regarded as a potential candidate for catalytic conversion of biomass-derived syngas to mixed alcohols.« less

  17. A study of room-temperature LixMn1.5Ni0.5O4 solid solutions

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Saravanan, Kuppan; Jarry, Angelique; Kostecki, Robert; Chen, Guoying

    2015-01-26

    Understanding the kinetic implication of solid-solution vs. biphasic reaction pathways is critical for the development of advanced intercalation electrode materials. Yet this has been a long-standing challenge in materials science due to the elusive metastable nature of solid solution phases. The present study reports the synthesis, isolation, and characterization of room-temperature LixMn1.5Ni0.5O4 solid solutions. In situ XRD studies performed on pristine and chemically-delithiated, micron-sized single crystals reveal the thermal behavior of LixMn1.5Ni0.5O4 (0 ≤ x ≤ 1) cathode material consisting of three cubic phases: LiMn1.5Ni0.5O4 (Phase I), Li0.5Mn1.5Ni0.5O4 (Phase II) and Mn1.5Ni0.5O4 (Phase III). A phase diagram capturing the structuralmore » changes as functions of both temperature and Li content was established. In conclusion, the work not only demonstrates the possibility of synthesizing alternative electrode materials that are metastable in nature, but also enables in-depth evaluation on the physical, electrochemical and kinetic properties of transient intermediate phases and their role in battery electrode performance.« less

  18. Phase transformation during mechano-synthesis of nanocrystalline/amorphous Fe32Mn6Si alloys

    SciTech Connect (OSTI)

    Amini, Rasool; Shamsipoor, Ali; Ghaffari, Mohammad; Alizadeh, Morteza; Okyay, Ali Kemal

    2013-10-15

    Mechano-synthesis of Fe32Mn6Si alloy by mechanical alloying of the elemental powder mixtures was evaluated by running the ball milling process under an inert argon gas atmosphere. In order to characterize the as-milled powders, powder sampling was performed at predetermined intervals from 0.5 to 192 h. X-ray florescence analyzer, X-ray diffraction, scanning electron microscope, and high resolution transmission electron microscope were utilized to investigate the chemical composition, structural evolution, morphological changes, and microstructure of the as-milled powders, respectively. According to the results, the nanocrystalline FeMnSi alloys were completely synthesized after 48 h of milling. Moreover, the formation of a considerable amount of amorphous phase during the milling process was indicated by quantitative X-ray diffraction analysis as well as high resolution transmission electron microscopy image and its selected area diffraction pattern. It was found that the ?-to-? and subsequently the amorphous-to-crystalline (especially martensite) phase transformation occurred by milling development. - Graphical abstract: Mechano-synthesis of nanocrystalline/amorphous Fe32Mn6Si shape memory alloys in the powder form: amorphous phase formation, ?-to-? phase transformation, mechano-crystallization of the amorphous, and martensite phase formation during the process. Highlights: During MA, the ?-to-? phase transformation and amorphization occurred. Mechano-crystallization of the amorphous phase occurred at sufficient milling time. The formation of high amount of ?-martensite was evidenced at high milling times. The platelet, spherical, and then irregular particle shapes was extended by MA. By MA, the particles size was increased, then reduced, and afterward re-increased.

  19. Structural and Chemical Evolution of Li- and Mn-rich Layered Cathode Material

    SciTech Connect (OSTI)

    Zheng, Jianming; Xu, Pinghong; Gu, Meng; Xiao, Jie; Browning, Nigel D.; Yan, Pengfei; Wang, Chong M.; Zhang, Jiguang

    2015-02-24

    Lithium (Li)- and manganese-rich (LMR) layered-structure materials are very promising cathodes for high energy density lithium-ion batteries. However, their voltage fading mechanism and its relationships with fundamental structural changes are far from being sufficiently understood. Here we report the detailed phase transformation pathway in the LMR cathode (Li[Li0.2Ni0.2Mn0.6]O2) during cycling for the samples prepared by hydro-thermal assistant method. It is found the transformation pathway of LMR cathode is closely correlated to its initial structure and preparation conditions. The results reveal that LMR cathode prepared by HA approach experiences a phase transformation from the layered structure to a LT-LiCoO2 type defect spinel-like structure (Fd-3m space group) and then to a disordered rock-salt structure (Fm-3m space group). The voltage fade can be well correlated with the Li ion insertion into octahedral sites, rather than tetrahedral sites, in both defect spinel-like structure and disordered rock-salt structure. The reversible Li insertion/removal into/from the disordered rock-salt structure is ascribed to the Li excess environment that can satisfy the Li percolating in the disordered rock-salt structure despite the increased kinetic barrier. Meanwhile, because of the presence of a great amount of oxygen vacancies, a significant decrease of Mn valence is detected in the cycled particle, which is below that anticipated for a potentially damaging Jahn-Teller distortion (+3.5). Clarification of the phase transformation pathway, cation redistribution, oxygen vacancy and Mn valence change undoubtedly provides insights into a profound understanding on the voltage fade, and capacity degradation of LMR cathode. The results also inspire us to further enhance the reversibility of LMR cathode via improving its surface structural stability.

  20. Generation and control of spin-polarized photocurrents in GaMnAs heterostructures

    SciTech Connect (OSTI)

    Bezerra, Anibal T. Farinas, Paulo F.; Studart, Nelson; Degani, Marcos H.; Maialle, Marcelo Z.

    2014-01-13

    Photocurrents are calculated for a specially designed GaMnAs semiconductor heterostructure. The results reveal regions in the infrared range of the energy spectrum, in which the proposed structure is remarkably spin-selective. For such photon energies, the generated photocurrents are strongly spin-polarized. Application of a relatively small static bias in the growth direction of the structure is predicted to efficiently reverse the spin-polarization for some photon energies. This behavior suggests the possibility of conveniently simple switching mechanisms. The physics underlying the results is studied and understood in terms of the spin-dependent properties emerging from the particular potential profile of the structure.

  1. Magnetic and transport properties of Mn{sub 2}CoAl oriented films

    SciTech Connect (OSTI)

    Jamer, Michelle E.; Assaf, Badih A.; Devakul, Trithep; Heiman, Don

    2013-09-30

    The structure, magnetic, and transport properties of thin films of the Heusler ferrimagnet Mn{sub 2}CoAl have been investigated for properties related to spin gapless semiconductors. Oriented films were grown by molecular beam epitaxy on GaAs substrates and the structure was found to transform from tetragonal to cubic for increasing annealing temperature. The anomalous Hall resistivity is found to be proportional to the square of the longitudinal resistivity and magnetization expected for a topological Berry curvature origin. A delicate balance of the spin-polarized carrier type when coupled with voltage gate-tuning could significantly impact advanced electronic devices.

  2. Magnetic domain wall manipulation in (Ga,Mn)As nanostructures for spintronic applications

    SciTech Connect (OSTI)

    Wosinski, Tadeusz; Andrearczyk, Tomasz; Figielski, Tadeusz; Olender, Karolina; Wrobel, Jerzy

    2014-02-21

    Ring-shaped nanostructures have been designed and fabricated by electron-beam lithography patterning and chemical etching from thin epitaxial layers of the ferromagnetic semiconductor (Ga,Mn)As. The nanostructures, in a form of planar rings with a slit, were supplied with four electrical terminals and subjected to magneto-transport studies under planar weak magnetic field. Magnetoresistive effects caused by manipulation of magnetic domain walls and magnetization reversal in the nanostructures have been investigated and possible applications of the nanostructures as four-terminal spintronic devices are discussed.

  3. Magnetocrystalline anisotropy in UMn2Ge2 and related Mn-based actinide ferromagnets

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Parker, David S.; Ghimire, Nirmal; Singleton, John; Thompson, J. D.; Bauer, Eric D.; Baumbach, Ryan; Mandrus, David; Li, Ling; Singh, David J.

    2015-05-04

    We presenmore » t magnetization isotherms in pulsed magnetic fields up to 62 Tesla, supported by first principles calculations, demonstrating a huge uniaxial magnetocrystalline anisotropy energy - approximately 20 MJ/m3 - in UMn2Ge2. This large anisotropy results from the extremely strong spin-orbit coupling affecting the uranium 5 f electrons, which in the calculations exhibit a substantial orbital moment exceeding 2 μB. Finally, we also find from theoretical calculations that a number of isostructural Mn-actinide compounds are expected to have similarly large anisotropy.« less

  4. Magnetocrystalline Anisotropy in UMn2Ge2 and Related Mn-based Actinide Ferromagnets

    SciTech Connect (OSTI)

    Parker, David S; Mandrus, D.; Ghimire, N J; Baumbach, Ryan; Singleton, John; Thompson, J.D.; Bauer, Eric D.; Li, Ling; Singh, David J

    2015-01-01

    We present magnetization isotherms in pulsed magnetic fields up to 62 Tesla, supported by first principles calculations, demonstrating a huge uniaxial magnetocrystalline anisotropy energy - approximately 20 MJ/m3 - in UMn2Ge2. This large anisotropy results from the extremely strong spin-orbit coupling affecting the uranium 5 f electrons, which in the calculations exhibit a substantial orbital moment exceeding 2 Bohr magnetons. We also find from theoretical calculations that a number of isostructural Mn-actinide compounds are expected to have similarly large anisotropy.

  5. Spin Hall effect-controlled magnetization dynamics in NiMnSb

    SciTech Connect (OSTI)

    Dürrenfeld, P. Ranjbar, M.; Gerhard, F.; Gould, C.; Molenkamp, L. W.; Åkerman, J.

    2015-05-07

    We investigate the influence of a spin current generated from a platinum layer on the ferromagnetic resonance (FMR) properties of an adjacent ferromagnetic layer composed of the halfmetallic half-Heusler material NiMnSb. Spin Hall nano-oscillator devices are fabricated, and the technique of spin torque FMR is used to locally study the magnetic properties as in-plane anisotropies and resonance fields. A change in the FMR linewidth, in accordance with the additional spin torque produced by the spin Hall effect, is present for an applied dc current. For sufficiently large currents, this should yield auto-oscillations, which however are not achievable in the present device geometry.

  6. Vacancy dynamic in Ni-Mn-Ga ferromagnetic shape memory alloys

    SciTech Connect (OSTI)

    Merida, D.; Snchez-Alarcos, V.; Prez-Landazbal, J. I.; Recarte, V.; Plazaola, F.

    2014-06-09

    Vacancies control any atomic ordering process and consequently most of the order-dependent properties of the martensitic transformation in ferromagnetic shape memory alloys. Positron annihilation spectroscopy demonstrates to be a powerful technique to study vacancies in NiMnGa alloys quenched from different temperatures and subjected to post-quench isothermal annealing treatments. Considering an effective vacancy type the temperature dependence of the vacancy concentration has been evaluated. Samples quenched from 1173?K show a vacancy concentration of 1100??200?ppm. The vacancy migration and formation energies have been estimated to be 0.55??0.05?eV and 0.90??0.07?eV, respectively.

  7. Direct evidence of detwinning in polycrystalline Ni-Mn-Ga ferromagnetic shape memory alloys during deformation.

    SciTech Connect (OSTI)

    Nie, Z. H.; Lin Peng, R.; Johansson, S.; Oliver, E. C.; Ren, Y.; Wang, Y. D.; Liu, Y. D.; Deng, J. N.; Zuo, L.; Brown, D. E.; Northwestern Univ., China; Linkoping Univ.; Rutherford Appleton Lab.; Northern Illinois Univ.

    2008-01-01

    In situ time-of-flight neutron diffraction and high-energy x-ray diffraction techniques were used to reveal the preferred reselection of martensite variants through a detwinning process in polycrystalline Ni-Mn-Ga ferromagnetic shape memory alloys under uniaxial compressive stress. The variant reorientation via detwinning during loading can be explained by considering the influence of external stress on the grain/variant orientation-dependent distortion energy. These direct observations of detwinning provide a good understanding of the deformation mechanisms in shape memory alloys.

  8. Magnetoelastic Coupling and Symmetry Breaking in the Frustrated Antiferromagnet {alpha}-NaMnO{sub 2}

    SciTech Connect (OSTI)

    Giot, Maud; Chapon, Laurent C.; Radaelli, Paolo G.; Androulakis, John; Lappas, Alexandros; Green, Mark A.

    2007-12-14

    The magnetic and crystal structures of the {alpha}-NaMnO{sub 2} have been determined by high-resolution neutron powder diffraction. The system maps out a frustrated triangular spin lattice with anisotropic interactions that displays two-dimensional spin correlations below 200 K. Magnetic frustration is lifted through magneto-elastic coupling, evidenced by strong anisotropic broadening of the diffraction profiles at high temperature and ultimately by a structural phase transition at 45 K. In this low-temperature regime a three-dimensional antiferromagnetic state is observed with a propagation vector k=((1/2),(1/2),0)

  9. Half metallic ferromagnetism in alkali metal nitrides MN (M = Rb, Cs): A first principles study

    SciTech Connect (OSTI)

    Murugan, A. Rajeswarapalanichamy, R. Santhosh, M. Sudhapriyanga, G.; Kanagaprabha, S.

    2014-04-24

    The structural, electronic and elastic properties of two alkali metal nitrides (MN: M= Rb, Cs) are investigated by the first principles calculations based on density functional theory using the Vienna ab-initio simulation package. At ambient pressure the two nitrides are stable in ferromagnetic state with CsCl structure. The calculated lattice parameters are in good agreement with the available results. The electronic structure reveals that these materials are half metallic in nature. A pressure-induced structural phase transition from CsCl to ZB phase is observed in RbN and CsN.

  10. Neutron structural characterization, inversion degree and transport properties of NiMn{sub 2}O{sub 4} spinel prepared by the hydroxide route

    SciTech Connect (OSTI)

    Sagua, A.; Lescano, Gabriela M.; Alonso, J.A.; Martínez-Coronado, R.; Fernández-Díaz, M.T.; Morán, E.

    2012-06-15

    Graphical abstract: A pure specimen has been synthesized by the hydroxide route. This spinel, studied by NPD, shows an important inversion degree, λ = 0.80. A bond-valence study shows that the tetrahedral Mn ions are divalent whereas the octahedral Mn and Ni are slightly oxidized from the expected 3+ and 2+ values, respectively. The mixed valence Mn{sup 3+}/Mn{sup 4+} accounts for a hopping mechanism between adjacent octahedral sites, leading to a significant conductivity. Highlights: ► A low-temperature hydroxide route allowed preparing almost pure specimens of NiMn{sub 2}O{sub 4}. ► NPD essential to determine inversion degree; contrasting Ni and Mn for neutrons. ► Bond valence establishes valence state of octahedral and tetrahedral Ni and Mn ions. ► Thermal analysis, transport measurements complement characterization of this oxide. ► A structure–properties relationship is established. -- Abstract: The title compound has been synthesized by the hydroxide route. The crystal structure has been investigated at room temperature from high-resolution neutron powder diffraction (NPD) data. It crystallizes in a cubic spinel structure, space group Fd3{sup ¯}m, Z = 8, with a = 8.3940(2) Å at 295 K. The crystallographic formula is (Ni{sub 0.202(1)}Mn{sub 0.798(1)}){sub 8a}(Ni{sub 0.790(1)}Mn{sub 1.210(1)}){sub 16d}O{sub 4} where 8a and 16d stand for the tetrahedral and octahedral sites of the spinel structure, respectively. There is a significant inversion degree of the spinel structure, λ = 0.80. In fact, the variable parameter for the oxygen position, u = 0.2636(4), is far from that expected (u = 0.25) for normal spinels. From a bond-valence study, it seems that the valence distribution in NiMn{sub 2}O{sub 4} spinel is not as trivial as expected (Ni{sup 2+} and Mn{sup 3+}), but clearly the tetrahedral Mn ions are divalent whereas the octahedral Mn and Ni are slightly oxidized from the expected +3 and +2 values, respectively. The mixed valence observed at

  11. Investigation on structural, optical and magnetic properties of double perovskite Gd{sub 2}NiMnO{sub 6}

    SciTech Connect (OSTI)

    Mohapatra, S. R.; Sahu, B.; Raut, S.; Singh, A. K.; Kaushik, S. D.

    2015-06-24

    Single phase double perovskite Gd{sub 2}NiMnO{sub 6} was prepared by conventional solid state reaction route. X-ray diffraction (XRD) result reveals that the compound possess monoclinic structure with space group P2{sub 1}/n. Optical characterization performed at room temperature via UV-visible spectroscopy confirms Gd{sub 2}NiMnO{sub 6} as a direct band-gap material with band gap of ∼1.5 eV. Magnetization measurement in Zero field cooled (ZFC) condition at H = 100 Oe shows magnetic transition at ∼ 125 K. Due to competing interactions between magnetic ions (Ni{sup 2+} and Mn{sup 4+}), we could observe two magnetic transition below 40 K.

  12. Depth-dependent magnetism in epitaxial MnSb thin films: effects of surface passivation and cleaning

    SciTech Connect (OSTI)

    Aldous J. D.; Sanchez-Hanke C.; Burrows, C.W.; Maskery, I.; Brewer, M.S.; Hase, T.P.A.; Duffy, J.A.; Lees, M. Rs; Decoster, T.; Theis, W.; Quesada, A.; Schmid, A.K.; Bell, G.R.

    2012-03-15

    Depth-dependent magnetism in MnSb(0001) epitaxial films has been studied by combining experimental methods with different surface specificities: polarized neutron reflectivity, x-ray magnetic circular dichroism (XMCD), x-ray resonant magnetic scattering and spin-polarized low energy electron microscopy (SPLEEM). A native oxide {approx}4.5 nm thick covers air-exposed samples which increases the film's coercivity. HCl etching efficiently removes this oxide and in situ surface treatment of etched samples enables surface magnetic contrast to be observed in SPLEEM. A thin Sb capping layer prevents oxidation and preserves ferromagnetism throughout the MnSb film. The interpretation of Mn L{sub 3,2} edge XMCD data is discussed.

  13. Site preference and compensation behavior in Co(Cr, Mn){sub 2}O{sub 4} system

    SciTech Connect (OSTI)

    Zhang, H. G.; Wang, Z.; Yue, M.; Liu, E. K.; Wang, W. H.; Wu, G. H.

    2015-05-07

    Site preference of doped Mn ions in CoCr{sub 2−x}Mn{sub x}O{sub 4} (x = 0–2) series has been derived separately from structure and magnetic measurement. It shows that parts of the doped Mn ions occupy the A (Co) sites when x < 0.5. And then, it takes the two B (Cr) sites in turn before and after x = 1.3. This site preference behavior results in a role conversion of the magnetic contributors and, thus, leads to the composition dependent magnetic compensation. Temperature induced compensation and negative magnetization have also been found in several samples, which is attributed to the large energy barrier between the ferromagnetic and antiferromagnetic spin arrangement. A structure transition from cubic to tetragonal symmetry has been detected.

  14. Calculations of structural, elastic, electronic, magnetic and phonon properties of FeNiMnAl by the first principles

    SciTech Connect (OSTI)

    U?ur, ?ule; ?yigr, Ahmet

    2014-10-06

    The electronic, elastic and dynamical properties of the quaternary alloy FeNiMnAl have been investigated using a pseudopotential plane wave method within the generalized gradient approximation (GGA). We determined the lattice parameters and the bulk modulus B. In addition, the elastic properties such as elastic constans (C{sub 11}, C{sub 12} and C{sub 44}), the shear modulus G, the young modulus E, the poisson's ratio ? and the B/G ratio are also given. The FeNiMnAl Heusler alloy exhibit a ferromagnetic half-metallic behavior with the total magnetic moment of 4.02 ?{sub B}. The phonon dispersion of FeNiMnAl has been performed using the density functional theory and the direct method with 222 supercell.

  15. Electronic phase separation in lanthanum manganites: Evidence from {sup 55}Mn NMR

    SciTech Connect (OSTI)

    Allodi, G.; De Renzi, R.; Guidi, G.; Licci, F.; Pieper, M.W.

    1997-09-01

    {sup 55}Mn NMR experiments were carried out at 1.3{endash}4.2 K on six samples of lanthanum manganites, with a hole doping concentration ranging from the antiferromagnetic-insulator to the ferromagnetic-conductor region of the phase diagram. The dependence of the resonance frequencies on external fields is either as expected for ferromagnets (FM) or for antiferromagnets (AF). No indication of a canted phase could be detected. FM and AF resonances were found to coexist in all samples and are grouped in three broad bands, whose frequencies do not depend in first order on hole concentration. Strong evidence of interaction between AF and FM regions was provided by longitudinal relaxation experiments in several samples. An explanation of this behavior is offered in terms of intrinsic phase separation of the holes into FM microdomains. We determine the {sup 55}Mn hyperfine coupling to be isotropic in all cases, with A=6.2T/{mu}{sub B} for the on-site term in the AF domains. {copyright} {ital 1997} {ital The American Physical Society}

  16. Itinerant Antiferromagnetism in FeMnP0.8Si0.2

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Sales, Brian C.; Susner, Michael A.; Conner, Benjamin S.; Yan, Jiaqiang Q.; May, Andrew F.

    2015-09-25

    Compounds based on the Fe2P structure have continued to attract interest because of the interplay between itinerant and localized magnetism in a noncentrosymmetric crystal structure, and because of the recent developments of these materials for magnetocaloric applications. We report the growth and characterization of millimeter-sized single crystals of FeMnP0.8Si0.2 with the Fe2P structure. Single-crystal x-ray diffraction, magnetization, resistivity, and Hall and heat capacity data are reported. The crystals exhibit itinerant antiferromagnetic order below 158 K with no hint of ferromagnetic behavior in the magnetization curves and with the spins ordered primarily in the ab plane. The room-temperature resistivity is closemore » to the Ioffe-Regel limit for a metal. Single-crystal x-ray diffraction indicates a strong preference for Mn to occupy the larger pyramidal 3g site. The cation site preference in the as-grown crystals and the antiferromagnetism were not changed after high-temperature anneals and a rapid quench to room temperature« less

  17. Nanofiber of Mn{sub 3}O{sub 4}: Fabrication and application as supercapacitor electrode

    SciTech Connect (OSTI)

    Bhagwan, Jai; Sharma, Yogesh; Yadav, K. L.

    2015-06-24

    Mn{sub 3}O{sub 4}–nanofiber with high aspect ratio is prepared by a simple electrospinning process. The thermal, structural and morphological characterizations are carried out by TGA, XRD and FESEM, respectively. To assess the property of nanofiber for the use in supercapacitors, cyclic voltammetry (CV) and galvanostatic charging-discharging (GCD) are performed in 2M KOH electrolyte with the potential window ranging from +0.42V to −0.45V. Effect of polymer concentration and electric field intensity on the diameter of as-spun nanofiber was studied. Further, appropriate heating rate was used for sintering to obtain aligned nanofiber. High specific capacitance of 150(±5) F g{sup −1} is obtained by Mn{sub 3}O{sub 4} nanofibers. The rate performance is also found to be good. This improved performance in terms of high specific capacitance and rate capability is ascribed to the nanofabric morphology which provides more active sites and easy access path for ions/electrons.

  18. Thermochemical generation of hydrogen and oxygen from water. [NaMnO/sub 2/ and TiO/sub 2/

    DOE Patents [OSTI]

    Robinson, P.R.; Bamberger, C.E.

    1980-02-08

    A thermochemical cyclic process for the production of hydrogen exploits the reaction between sodium manganate (NaMnO/sub 2/) and titanium dioxide (TiO/sub 2/) to form sodium titanate (Na/sub 2/TiO/sub 3/), manganese (II) titanate (MnTiO/sub 3/) and oxygen. The titanate mixture is treated with sodium hydroxide, in the presence of steam, to form sodium titanate, sodium manganate (III), water and hydrogen. The sodium titanate-manganate (III) mixture is treated with water to form sodium manganate (III), titanium dioxide and sodium hydroxide. Sodium manganate (III) and titanium dioxide are recycled following dissolution of sodium hydroxide in water.

  19. Influence of defects on the structural and magnetic properties of multifunctional La2NiMnO6 thin films

    SciTech Connect (OSTI)

    Guo, HZ; Burgess, J; Ada, E; Street, S; Gupta, A.; Iliev, M N; Kellock, A J; Magen Dominguez, Cesar; Varela del Arco, Maria; Pennycook, Stephen J

    2008-01-01

    Thin films of the double perovskite La2NiMnO6 (LNMO) have been grown on various lattice-matched substrates (SrTiO3, LaAlO3, NdGaO3 and MgO) by pulsed laser deposition under varying oxygen background pressure (25 - 800 mTorr). The out-of-plane lattice constant of the LNMO film initially decreases with increasing pressure, likely caused by a reduction in the defect concentration and improved structural ordering, before leveling off at higher pressures. Scanning transmission electron microscopy results show that the films are epitaxial, and the interface is sharp and coherent. While very few defects are observed by STEM in a film grown at high oxygen pressure (800 mTorr), a film grown at a lower pressure (100 mTorr) shows the formation of defects that extend throughout the thickness except for a very thin layer near the interface. The Raman spectra of the films are dominated by two broad peaks at around 540 cm-1 and 685 cm-1, which are assigned to the antisymmetric stretching (AS) and symmetric stretching (S) modes of MnO6 and NiO6 octahedra, respectively. The Raman peaks of the LNMO thin films grown in 800 mTorr background O2 are blue shifted in comparison to those of LNMO bulk, and the shift increases with decreasing film thickness, indicating the increased influence of strain. The critical thickness for strain relaxation as determined from the Raman spectra is between 40 - 80 nm. The strain is observed to have a negligible influence on the magnetic properties for films grown at high oxygen pressures. However, films grown at low pressures exhibit degraded magnetic properties, which can be attributed to a combination of B-site cation disorder and an increase in the concentration of Mn3+ and Ni3+ Jahn-Teller ions caused by oxygen defects. With increasing oxygen pressure during growth, the paramagnetic-ferromagnetic transition temperature (~280 K) gets sharper and the saturation magnetization at low temperatures is enhanced. Based on electron energy loss spectroscopy

  20. Spectroscopic and magnetic properties of Mn doped GaN epitaxial films grown by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Vidyasagar, R.; Lin, Y.-T.; Tu, L.-W.

    2012-12-15

    Graphical abstract: We report here that micro-Raman scattering spectrum for Mn doped GaN thin film has displayed a new peak manifested at 578 cm{sup −1}, by which it is attributed to interior LVM originated by the incorporation of Mn ions in place of Ga sites. Mn doped GaN thin film also showed the typical negative magnetoresistance up to ∼50 K, revealing that the film showed magnetic ordering of spins below 50 K. Display Omitted Highlights: ► GaN and Mn doped GaN single phase wurtzite structures grown by PAMBE. ► The phase purity of the epilayers investigated by HRXRD, HRSEM and EDX. ► The red shift in near band edge emission has been observed using micro-PL. ► A new peak related LVM at 578 cm{sup −1} in micro-Raman scattering measurements confirmed Mn doped into GaN. ► Negative-magnetoresistance investigations have showed that the film has T{sub c} < 50 K. -- Abstract: Spectroscopic and magnetic properties of Mn doped GaN, and GaN epitaxial films have been investigated by employing micro-photoluminescence, micro-Raman, and temperature dependent magneto-resistance measurements. The HR-XRD profiles have shown that the epitaxial films are in hexagonal wurtzite structures. Morphology and composition of the films have been examined by field emission scanning electron microscopy, and energy-dispersive X-ray analysis. Micro-photoluminescence spectrum displayed a dominant near band edge emission at 362 nm, which is assigned to near band edge transition within the hexagonal structure of GaN. Raman scattering profiles showed a new vibrational mode at 578 cm{sup −1}, which is attributed to the vacancy-related local vibrational mode of Mn occupying the Ga site. Temperature dependent negative magnetoresistance measurements provide a direct evidence of magnetic ordering below 50 K for the Mn doped GaN thin film.

  1. Suppression of the thermal hysteresis in magnetocaloric MnAs thin film by highly charged ion bombardment

    SciTech Connect (OSTI)

    Trassinelli, M. Marangolo, M.; Eddrief, M.; Etgens, V. H.; Gafton, V.; Hidki, S.; Lacaze, E.; Lamour, E.; Prigent, C.; Rozet, J.-P.; Steydli, S.; Zheng, Y.; Vernhet, D.

    2014-02-24

    We present the investigation on the modifications of structural and magnetic properties of MnAs thin film epitaxially grown on GaAs induced by slow highly charged ions bombardment under well-controlled conditions. The ion-induced defects facilitate the nucleation of one phase with respect to the other in the first-order magneto-structural MnAs transition, with a consequent suppression of thermal hysteresis without any significant perturbation on the other structural and magnetic properties. In particular, the irradiated film keeps the giant magnetocaloric effect at room temperature opening new perspective on magnetic refrigeration technology for everyday use.

  2. A determination of the oxygen non-stoichiometry of the oxygen storage material YBaMn{sub 2}O{sub 5+δ}

    SciTech Connect (OSTI)

    Jeamjumnunja, Kannika; Gong, Wenquan; Makarenko, Tatyana; Jacobson, Allan J.

    2015-10-15

    The A-site ordered double-perovskite oxide, YBaMn{sub 2}O{sub 5+δ}, has been of recent interest for possible application as an oxygen storage material. In the present study, the oxygen non-stoichiometry of YBaMn{sub 2}O{sub 5+δ} has been determined as a function of pO{sub 2} at 650, 700 and 750 °C by Coulometric titration at near-equilibrium conditions. The results confirm that this perovskite oxide has three distinct phases on oxidation/reduction with δ≈0, 0.5 and 1. The stabilities of the YBaMn{sub 2}O{sub 5+δ} phases span a wide range of oxygen partial pressures (∼10{sup −20}≤pO{sub 2}(atm)≤∼1 ) depending on temperature. The phases interconvert at higher pO{sub 2} values at higher temperatures. The partial molar free energies (Δμ{sub O}) corresponding to the oxidation of YBaMn{sub 2}O{sub 5} to YBaMn{sub 2}O{sub 5.5} and of YBaMn{sub 2}O{sub 5.5} to YBaMn{sub 2}O{sub ∼6} were determined. The value of Δμ{sub O} in both oxidation steps becomes less negative with increasing temperature. At some T and pO{sub 2} conditions, YBaMn{sub 2}O{sub 5+δ} is unstable with respect to decomposition to BaMnO{sub 3−δ} and YMnO{sub 3}. This instability is anticipated from the previous studies of the synthesis of YBaMn{sub 2}O{sub 5+δ} but is more apparent in the present experiments which are necessarily slow in order to achieve equilibrium with respect to the oxygen content. - Highlights: • Determination of the oxygen non-stoichiometry of YBaMn{sub 2}O{sub 5+δ} as a function of pO{sub 2} and T. • Establishments of pO{sub 2} ranges of stability of O{sub 5} and O{sub 5.5} at 650 °C, 700 °C and 750 °C. • Discovery of the kinetic instability of YBaMn{sub 2}O{sub 5+δ} with respect to decomposition to BaMnO{sub 3}−{sub x} and YMnO{sub 3}. • Evaluation of the thermodynamics of the oxidation of YBaMnO{sub 5}.

  3. Electronic and magnetic properties of double perovskite Dy{sub 2}MnCoO{sub 6} by first-principles calculation

    SciTech Connect (OSTI)

    Ganeshraj, C.; Santhosh, P. N.

    2014-05-07

    Using first-principles calculation, we investigate electronic and magnetic properties of Dy{sub 2}MnCoO{sub 6}. A detailed structural optimization has been done and found that the orthorhombic structure with Mn (Co) ions aligning along the longest axis type is the most stable structure. Within the generalized gradient approximation, the spin polarized calculations predict Dy{sub 2}MnCoO{sub 6} to be a half-metallic with ferromagnetic interaction between Mn and Co ions and antiferromagnetic interaction between Dy and Mn/Co ions. We also investigate the effect of Hubbard parameter (U) on the ground state magnetic structure. For all values of Hubbard U parameter the Co ions have nonzero magnetic moment; they do not lie in low-spin state, as in DyCoO{sub 3}.

  4. Electrochemically induced deposition method to prepare {gamma}-MnO{sub 2}/multi-walled carbon nanotube composites as electrode material in supercapacitors

    SciTech Connect (OSTI)

    Fan Zhen

    2008-08-04

    The {gamma}-MnO{sub 2}/multi-walled carbon nanotube ({gamma}-MnO{sub 2}/MWNT) composite has been prepared by electrochemically induced deposition method. The morphology and crystal structure of the composite were investigated by X-ray diffraction and scanning electron microscopy, respectively. The capacitive properties of the {gamma}-MnO{sub 2}/MWNT composite have been investigated by cyclic voltammetry (CV). A specific capacitance (based on {gamma}-MnO{sub 2}) as high as 579 F g{sup -1} is obtained at a scan rate of 10 mV s{sup -1} in 0.1 M Na{sub 2}SO{sub 4} aqueous solution. Additionally, the {gamma}-MnO{sub 2}/MWNT composite electrode shows excellent long-term cycle stability (only 2.4% decrease of the specific capacitance is observed after 500 CV cycles)

  5. CdSe/ZnSe quantum dot with a single Mn{sup 2+} ionA new system for a single spin manipulation

    SciTech Connect (OSTI)

    Smole?ski, T.

    2015-03-21

    We present a magneto-optical study of individual self-assembled CdSe/ZnSe quantum dots doped with single Mn{sup 2+} ions. Properties of the studied dots are analyzed analogously to more explored system of Mn-doped CdTe/ZnTe dots. Characteristic sixfold splitting of the neutral exciton emission line as well as its evolution in the magnetic field are described using a spin Hamiltonian model. Dynamics of both exciton recombination and Mn{sup 2+} spin relaxation are extracted from a series of time-resolved experiments. Presence of a single dopant is shown not to affect the average excitonic lifetime measured for a number of nonmagnetic and Mn-doped dots. On the other hand, non-resonant pumping is demonstrated to depolarize the Mn{sup 2+} spin in a quantum dot placed in external magnetic field. This effect is utilized to determine the ion spin relaxation time in the dark.

  6. Induced Ti magnetization at La0.7Sr0.3MnO3 and BaTiO3 interfaces

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Liu, Yaohua; Tornos, J.; te Velthuis, S. G. E.; Freeland, J. W.; Zhou, H.; Steadman, P.; Bencok, P.; Leon, C.; Santamaria, J.

    2016-04-01

    In artificial multiferroics hybrids consisting of ferromagnetic La0.7Sr0.3MnO3 (LSMO) and ferroelectric BaTiO3 epitaxial layers, net Ti moments are found from polarized resonant soft x-ray reflectivity and absorption. Moreover, the Ti dichroic reflectivity follows the Mn signal during the magnetization reversal, indicating exchange coupling between the Ti and Mn ions. But, the Ti dichroic reflectivity shows stronger temperature dependence than the Mn dichroic signal. Besides a reduced ferromagnetic exchange coupling in the interfacial LSMO layer, this may also be attributed to a weak Ti-Mn exchange coupling that is insufficient to overcome the thermal energy at elevated temperatures.

  7. Radiation-induced instability of MnS precipitates and its possible consequences on irradiation-induced stress corrosion cracking of austenitic stainless steels

    SciTech Connect (OSTI)

    Chung, H.M.; Sanecki, J.E.; Garner, F.A.

    1996-12-01

    Irradiation-assisted stress corrosion cracking (IASCC) is a significant materials issue for the light water reactor (LWR) industry and may also pose a problem for fusion power reactors that will use water as coolant. A new metallurgical process is proposed that involves the radiation-induced release into solution of minor impurity elements not usually thought to participate in IASCC. MnS-type precipitates, which contain most of the sulfur in stainless steels, are thought to be unstable under irradiation. First, Mn transmutes strongly to Fe in thermalized neutron spectra. Second, cascade-induced disordering and the inverse Kirkendall effect operating at the incoherent interfaces of MnS precipitates are thought to act as a pump to export Mn from the precipitate into the alloy matrix. Both of these processes will most likely allow sulfur, which is known to exert a deleterious influence on intergranular cracking, to re-enter the matrix. To test this hypothesis, compositions of MnS-type precipitates contained in several unirradiated and irradiated heats of Type 304, 316, and 348 stainless steels (SSs) were analyzed by Auger electron spectroscopy. Evidence is presented that shows a progressive compositional modification of MnS precipitates as exposure to neutrons increases in boiling water reactors. As the fluence increases, the Mn level in MnS decreases, whereas the Fe level increases. The S level also decreases relative to the combined level of Mn and Fe. MnS precipitates were also found to be a reservoir of other deleterious impurities such as F and O which could be also released due to radiation-induced instability of the precipitates.

  8. KINETICS OF Mn-BASED SORBENTS FOR HOT COAL GAS DESULFURIZATION

    SciTech Connect (OSTI)

    K.A. SADECKI; M.T. HEPWORTH

    1997-06-15

    Manganese-based sorbents have been investigated for the removal of hydrogen sulfide (the primary sulfur bearing compound) from hot coal gases. Four formulations of Mn-based sorbents were tested in an ambient-pressure fixed-bed reactor to determine steady state H2S concentrations, breakthrough times and effectiveness of the sorbent when subjected to cyclic sulfidation and regeneration testing. In previous reports, the sulfidation and regeneration results from cyclic testing done at 550 and 600 °C were presented. Manganese-based sorbents with molar ratios > 1:1 Mn:Substrate were effective in reducing the H2S concentration in simulated coal gases to less than 100 ppmv over five cycles. Actual breakthrough time for formulation C6-2-1100 was as high as 73% of breakthrough time based on wt% Mn in sorbent at 600 °C. Regeneration tests determined that loaded pellets can be essentially completely regenerated in air/steam mixture at 750 °C with minimal sulfate formation. In this report, the performance of the leading formulation (designated C6-2) was investigated for high temperature removal of H2S from simulated coal-derived fuel gas under varying sorbent induration temperature, reaction temperature, and superficial gas velocity. Sulfidation experiments were performed in an ambient pressure fixed-bed reactor between 500 °C and 600 °C. Four tests were conducted with each test consisting of four cycles of sulfidation and regeneration. Results showed that the induration temperature of the sorbent and the reaction temperature greatly affected the H2S removal capacity of the sorbent while the superficial gas velocity between 1090 and 1635 cm/min had minimal affect on the sorbent's breakthrough capacity. Sorbent also showed 30 to 53% loss of its strength over four cycles of sulfidation and regeneration. The former being sorbent indurated at 1115 °C and the prior being sorbent indurated at 1100 °C.

  9. Removal of Ca2+ from the Oxygen-Evolving Complex in Photosystem II Has Minimal Effect on the Mn4O5 Core Structure: A Polarized Mn X-ray Absorption Spectroscopy Study

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Lohmiller, Thomas; Shelby, Megan L.; Long, Xi; Yachandra, Vittal K.; Yano, Junko

    2015-05-19

    We studied Ca2+ -depleted and Ca2+ -reconstituted spinach photosystem II using polarized X-ray absorption spectroscopy of oriented PS II preparations to investigate the structural and functional role of the Ca2+ ion in the Mn4O5Ca cluster of the oxygen-evolving complex (OEC). Samples were prepared by low pH/citrate treatment as one-dimensionally ordered membrane layers and poised in the Ca2+ -depleted S1 (S1') and S2 (S2') states, the S2'YZ• state, at which point the catalytic cycle of water oxidation is inhibited, and the Ca2+ -reconstituted S1 state. Polarized Mn K-edge XANES and EXAFS spectra exhibit pronounced dichroism. Polarized EXAFS data of all statesmore » of Ca2+ -depleted PS II investigated show only minor changes in distances and orientations of the Mn-Mn vectors compared to the Ca2+ -containing OEC, which may be attributed to some loss of rigidity of the core structure. Thus, removal of the Ca2+ ion does not lead to fundamental distortion or rearrangement of the tetranuclear Mn cluster, which indicates that the Ca2+ ion in the OEC is not critical for structural maintenance of the cluster, at least in the S1 and S2 states, but fulfills a crucial catalytic function in the mechanism of the water oxidation reaction. On the basis of this structural information, reasons for the inhibitory effect of Ca2+ removal are discussed, attributing to the Ca2+ ion a fundamental role in organizing the surrounding (substrate) water framework and in proton-coupled electron transfer to YZ• (D1-Tyr161).« less

  10. Synthesis, crystal structure, and vibrational spectroscopic and UV-visible studies of Cs{sub 2}MnP{sub 2}O{sub 7}

    SciTech Connect (OSTI)

    Kaoua, Saida; Krimi, Saida; Pechev, Stanislav; Gravereau, Pierre; Chaminade, Jean-Pierre; Couzi, Michel; El Jazouli, Abdelaziz

    2013-02-15

    A new member of the A{sub 2}MP{sub 2}O{sub 7} diphosphate family, Cs{sub 2}MnP{sub 2}O{sub 7}, has been synthesized and structurally characterized. The crystal structure was determined by single crystal X-Ray diffraction. Cs{sub 2}MnP{sub 2}O{sub 7} crystallizes in the orthorhombic system, space group Pnma ( Music-Sharp-Sign 62), with the unit cell parameters a=16.3398(3), b=5.3872(1), c=9.8872(2) A, Z=4 and V=870.33(3) A{sup 3}. The structure parameters were refined to a final R{sub 1}/wR{sub 2}=0.0194/0.0441 for 1650 observed reflections. The 2D framework of Cs{sub 2}MnP{sub 2}O{sub 7} structure consists of P{sub 2}O{sub 7} and MnO{sub 5} units. The corner-shared MnO{sub 5} and P{sub 2}O{sub 7} units are alternately arranged along the b axis to form [(MnO)P{sub 2}O{sub 7}]{sub {infinity}} chains. These chains are interconnected by an oxygen atom to form sheets parallel to the (b, c) plane. The cesium atoms are located between the sheets in 9- and 10-fold coordinated sites. The infrared and Raman vibrational spectra have been investigated. A factor group analysis leads to the determination of internal modes of (P{sub 2}O{sub 7}) groups. UV-visible spectrum consists of weak bands, between 340 and 700 nm, assigned to the forbidden d-d transitions of Mn{sup 2+} ion, and of a strong band around 250 nm, attributed to the O--Mn charge transfer. - Graphical abstract: Structure of Cs{sub 2}MnP{sub 2}O{sub 7}: The 2D structure of Cs{sub 2}MnP{sub 2}O{sub 7} is built from P{sub 2}O{sub 7} diphosphate groups and MnO{sub 5} square pyramids which share corners and form [(MnO)P{sub 2}O{sub 7}]{sub {infinity}} chains along b axis. These chains are interconnected by an oxygen atom to form wavy (MnP{sub 2}O{sub 7}){sup 2-} sheets parallel to the (b, c) plane. The cesium ions are located between these sheets in the inter-layers space, in zigzag positions. Highlights: Black-Right-Pointing-Pointer A new diphosphate, Cs{sub 2}MnP{sub 2}O{sub 7}, has been synthesized and structurally

  11. Magnetic properties of MnSb inclusions formed in GaSb matrix directly during molecular beam epitaxial growth

    SciTech Connect (OSTI)

    Lawniczak-Jablonska, Krystyna; Wolska, Anna; Klepka, Marcin T.; Kret, Slawomir; Kurowska, Boguslawa; Kowalski, Bogdan J.; Twardowski, Andrzej; Wasik, Dariusz; Kwiatkowski, Adam; Sadowski, Janusz

    2011-04-01

    Despite of intensive search for the proper semiconductor base materials for spintronic devices working at room temperature no appropriate material based on ferromagnetic semiconductors has been found so far. We demonstrate that the phase segregated system with MnSb hexagonal inclusions inside the GaSb matrix, formed directly during the molecular beam epitaxial growth reveals the ferromagnetic properties at room temperature and is a good candidate for exploitation in spintronics. Furthermore, the MnSb inclusions with only one crystalline structure were identified in this GaMn:MnSb granular material. The SQUID magnetometry confirmed that this material exhibits ferromagnetic like behavior starting from helium up to room temperature. Moreover, the magnetic anisotropy was found which was present also at room temperature, and it was proved that by choosing a proper substrate it is possible to control the direction of easy axis of inclusions' magnetization moment between in-plane and out-of-plane; the latter is important in view of potential applications in spintronic devices.

  12. Structural, optical, and magnetic properties of Mn and Fe-doped Co{sub 3}O{sub 4} nanoparticles

    SciTech Connect (OSTI)

    Stella, C. Soundararajan, N.; Ramachandran, K.

    2015-08-15

    Mn and Fe-doped Co{sub 3}O{sub 4} nanoparticles were prepared by a simple precipitation method. The synthesized particles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and vibrating sample magnetometer (VSM) techniques. XRD analysis showed the cubic structure of Co{sub 3}O{sub 4}. SEM and TEM images confirmed the formation of interconnected nanoparticles. Mn and Fe-doped Co{sub 3}O{sub 4} showed broad absorption in the visible region compared to undoped sample and the band gap values are red shifted. Five Raman active modes were observed from the Raman spectra. FTIR spectra confirmed the spinel structure of Co{sub 3}O{sub 4} and the doping of Mn and Fe shifts the vibrational modes to lower wave number region. The magnetic measurements confirmed that Fe-doped Co{sub 3}O{sub 4} shows a little ferromagnetic behavior compared to undoped and Mn-doped Co{sub 3}O{sub 4}, which could be related to the uncompensated surface spins and the finite size effects.

  13. Excess Ni-doping induced enhanced room temperature magneto-functionality in Ni-Mn-Sn based shape memory alloy

    SciTech Connect (OSTI)

    Pramanick, S.; Giri, S.; Majumdar, S.; Chatterjee, S.

    2014-09-15

    Present work reports on the observation of large magnetoresistance (??30% at 80 kOe) and magnetocaloric effect (?12?Jkg{sup ?1}K{sup ?1} for 050 kOe) near room temperature (?290?K) on the Ni-excess ferromagnetic shape memory alloy Ni{sub 2.04}Mn{sub 1.4}Sn{sub 0.56}. The sample can be thought of being derived from the parent Ni{sub 2}Mn{sub 1.4}Sn{sub 0.6} alloy, where excess Ni was doped at the expense of Sn. Such Ni doping enhances the martensitic transition temperature and for the Ni{sub 2.04}Mn{sub 1.4}Sn{sub 0.56} it is found to be optimum (288?K). The doped alloy shows enhanced magneto-functional properties as well as reduced saturation magnetization as compared to the undoped counterpart at low temperature. A probable increment of antiferromagnetic correlation between Mn-atoms on Ni substitution can be accounted for the enhanced magneto-functional properties as well as reduction in saturation moment.

  14. Magnetic BiMn-α phase synthesis prediction: First-principles calculation, thermodynamic modeling and nonequilibrium chemical partitioning

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zhou, S. H.; Liu, C.; Yao, Y. X.; Du, Y.; Zhang, L. J.; Wang, C. -Z.; Ho, K. -M.; Kramer, M. J.

    2016-04-29

    BiMn-α is promising permanent magnet. Due to its peritectic formation feature, there is a synthetic challenge to produce single BiMn-α phase. The objective of this study is to assess driving force for crystalline phase pathways under far-from-equilibrium conditions. First-principles calculations with Hubbard U correction are performed to provide a robust description of the thermodynamic behavior. The energetics associated with various degrees of the chemical partitioning are quantified to predict temperature, magnetic field, and time dependence of the phase selection. By assessing the phase transformation under the influence of the chemical partitioning, temperatures, and cooling rate from our calculations, we suggestmore » that it is possible to synthesize the magnetic BiMn-α compound in a congruent manner by rapid solidification. The external magnetic field enhances the stability of the BiMn-α phase. In conclusion, the compositions of the initial compounds from these highly driven liquids can be far from equilibrium.« less

  15. Controlled fabrication and tunable photoluminescence properties of Mn{sup 2+} doped grapheneZnO composite

    SciTech Connect (OSTI)

    Luan, Xinglong; Zhang, Yihe Tong, Wangshu; Shang, Jiwu; An, Qi; Huang, Hongwei

    2014-11-15

    Highlights: GrapheneZnO composites were synthesized by a mixed solvothermal method. ZnO quantum dots are distributed uniformly on the graphene sheets. A possible hypothesis is raised for the influence of graphene oxide on the nucleation of ZnO. Mn{sup 2+} doped grapheneZnO composites were fabricated and the emission spectra can be tuned by doping. - Abstract: GrapheneZnO composites (GZnO) with controlled morphology and photoluminescence property were synthesized by a mixed solvothermal method. Mixed solvent were composed by dimethyl sulfoxide and ethylene glycol. Fourier transform infrared spectroscopy, transmission electron microscopy and photoluminescence spectra were used to characterize GZnO. Graphene as a substrate can help the distribution and the dispersity of ZnO, and a possible model of the interaction between graphene oxide and ZnO particles is proposed. At the same time, graphene also reduce the size of ZnO particles to about 5 nm. Furthermore, Mn{sup 2+} ions dopes GZnO successfully by the mixed solvothermal synthesis and the doping of Mn{sup 2+} makes GZnO shift red from 465 nm to 548 nm and 554 nm in the emission spectrum. The changes of the emission spectrum by the adding of Mn{sup 2+} make GZnO have tunable photoluminescence spectrum which is desirable for practical applications.

  16. CaMn2Sb2: Spin waves on a frustrated antiferromagnetic honeycomb lattice

    SciTech Connect (OSTI)

    McNally, D. E.; Simonson, J. W.; Kistner-Morris, J. J.; Smith, G. J.; Hassinger, J. E.; DeBeer-Schmidt, L.; Kolesnikov, A. I.; Zaliznyak, I.; Aronson, M. C.

    2015-05-22

    We present inelastic neutron scattering measurements of the antiferromagnetic insulator CaMn2Sb2:, which consists of corrugated honeycomb layers of Mn. The dispersion of magnetic excitations has been measured along the H and L directions in reciprocal space, with a maximum excitation energy of ≈ 24 meV. These excitations are well described by spin waves in a Heisenberg model, including first and second neighbor exchange interactions, J1 and J2, in the Mn plane and also an exchange interaction between planes. The determined ratio J2/J1 ≈ 1/6 suggests that CaMn2Sb2: is the first example of a compound that lies very close to the mean field tricritical point, known for the classical Heisenberg model on the honeycomb lattice, where the N´eel phase and two different spiral phases coexist. The magnitude of the determined exchange interactions reveal a mean field ordering temperature ≈ 4 times larger than the reported N´eel temperature TN = 85 K, suggesting significant frustration arising from proximity to the tricritical point.

  17. Unusual magnetic hysteresis and the weakened transition behavior induced by Sn substitution in Mn{sub 3}SbN

    SciTech Connect (OSTI)

    Sun, Ying, E-mail: sunying@buaa.edu.cn [Center for Condensed Matter and Materials Physics, Department of Physics, Beihang University, Beijing 100191 (China); International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Guo, Yanfeng; Li, Jun; Wang, Xia [Superconducting Properties Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Tsujimoto, Yoshihiro [Materials Processing Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan); Wang, Cong [Center for Condensed Matter and Materials Physics, Department of Physics, Beihang University, Beijing 100191 (China); Feng, Hai L.; Sathish, Clastin I.; Yamaura, Kazunari, E-mail: yamaura.kazunari@nims.go.jp [Superconducting Properties Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Matsushita, Yoshitaka [Analysis Station, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan)

    2014-01-28

    Substitution of Sb with Sn was achieved in ferrimagnetic antiperovskite Mn{sub 3}SbN. The experimental results indicate that with an increase in Sn concentration, the magnetization continuously decreases and the crystal structure of Mn{sub 3}Sb{sub 1-x}Sn{sub x}N changes from tetragonal to cubic phase at around x of 0.8. In the doping series, step-like anomaly in the isothermal magnetization was found and this behavior was highlighted at x?=?0.4. The anomaly could be attributed to the magnetic frustration, resulting from competition between the multiple spin configurations in the antiperovskite lattice. Meantime, H{sub c} of 18 kOe was observed at x?=?0.3, which is probably the highest among those of manganese antiperovskite materials reported so far. With increasing Sn content, the abrupt change of resistivity and the sharp peak of heat capacity in Mn{sub 3}SbN were gradually weakened. The crystal structure refinements indicate the weakened change at the magnetic transition is close related to the change of c/a ratio variation from tetragonal to cubic with Sn content. The results derived from this study indicate that the behavior of Mn{sub 3}Sb{sub 1-x}Sn{sub x}N could potentially enhance its scientific and technical applications, such as spin torque transfer and hard magnets.

  18. High Curie temperature of Ce-Fe-Si compounds with ThMn12 structure

    SciTech Connect (OSTI)

    Zhou, C; Pinkerton, FE; Herbst, JF

    2015-01-15

    We report the discovery of ternary CeFe(12-x)Si(x)compounds possessing the ThMn12 structure. The samples were prepared by melt spinning followed by annealing. In contrast to other known Ce Fe-based binary and ternary compounds, CeFe12-xSix compounds exhibit exceptionally high Curie temperatures whose values increase with added Si substitution. The highest T. = 583 K in CeFe10Si2 rivals that of the well-established Nd2Fe14B compound. We ascribe the T-c behavior to a combination of Si-induced 3d band structure changes and partial Ce3+ stabilization. (C) 2014 Published by Elsevier Ltd.

  19. Raman spectroscopy of InGaAs/GaAs nanoheterostructures δ-doped with Mn

    SciTech Connect (OSTI)

    Plankina, S. M.; Vikhrova, O. V.; Danilov, Yu. A.; Zvonkov, B. N.; Kalentyeva, I. L.; Nezhdanov, A. V.; Chunin, I. I.; Yunin, P. A.

    2015-01-15

    The results of complex studies of InGaAs/GaAs nanoheterostructures δ-doped with Mn are reported. The structures are grown by metal-organic vapor-phase epitaxy in combination with laser deposition. By confocal Raman spectroscopy, it is shown that the low-temperature δ-doped GaAs cap layers are of higher crystal quality compared to uniformly doped layers. Scattering of light in the coupled phonon-plasmon mode is observed. The appearance of this mode is conditioned by the diffusion of manganese from the δ-layer. The thickness of the cap layer is found to be d{sub c} ≈ 9–20 nm, optimal for attainment of the highest photoluminescence intensity of the quantum well and the highest layer concentration of holes by doping with manganese.

  20. Evidence of martensitic phase transitions in magnetic Ni-Mn-In thin films

    SciTech Connect (OSTI)

    Sokolov, A.; Zhang, Le; Dubenko, I.; Samanta, T.; Ali, N.; Stadler, S.

    2013-02-18

    Ni{sub 50}Mn{sub 35}In{sub 15} Heusler alloy thin films (with thicknesses of about 10 nm) have been grown on single crystal MgO and SrTiO{sub 3} (STO) (100) substrates using a laser-assisted molecular beam epitaxy method. Films of mixed austenitic and martensitic phases and of pure martensitic phase have been detected for those grown on MgO and STO substrates, respectively. Thermomagnetic curves were measured using a SQUID magnetometer and are consistent with those of off-stoichiometric In-based bulk Heusler alloys, including a martensitic transition at T = 315 K for films grown on MgO. The differences in the properties of the films grown on MgO and STO are discussed.

  1. Highly mobile type II twin boundary in Ni-Mn-Ga five-layered martensite

    SciTech Connect (OSTI)

    Sozinov, A.; Lanska, N.; Soroka, A.; Straka, L.

    2011-09-19

    Twin relationships and stress-induced reorientation were studied in Ni{sub 2}Mn{sub 1.14}Ga{sub 0.86} single crystal with five-layered modulated martensite crystal structure. Very low twinning stress of about 0.1 MPa was found for twin boundaries which deviated a few degrees from the (011) crystallographic plane. However, twin boundaries oriented exactly parallel to the (011) plane exhibited considerably higher level of twinning stress, above 1 MPa. X-ray diffraction experiments and calculations based on approximation of the martensite crystal lattice as a tetragonal lattice with a slight monoclinic distortion identified the two different kinds of twin interfaces as type II and type I twin boundaries.

  2. The magnetic ordering in high magnetoresistance Mn-doped ZnO thin films

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Venkatesh, S.; Baras, A.; Lee, J. -S.; Roqan, I. S.

    2016-03-24

    Here, we studied the nature of magnetic ordering in Mn-doped ZnO thin films that exhibited ferromagnetism at 300 K and superparamagnetism at 5 K. We directly inter-related the magnetisation and magnetoresistance by invoking the polaronpercolation theory and variable range of hopping conduction below the metal-to-insulator transition. By obtaining a qualitative agreement between these two models, we attribute the ferromagnetism to the s-d exchange-induced spin splitting that was indicated by large positive magnetoresistance (~40 %). Low temperature superparamagnetism was attributed to the localization of carriers and non-interacting polaron clusters. This analysis can assist in understanding the presence or absence of ferromagnetismmore » in doped/un-doped ZnO.« less

  3. High temperature dielectric relaxation anomaly of Y? and Mn? doped barium strontium titanate ceramics

    SciTech Connect (OSTI)

    Yan, Shiguang; Mao, Chaoliang E-mail: xldong@mail.sic.ac.cn; Wang, Genshui; Yao, Chunhua; Cao, Fei; Dong, Xianlin E-mail: xldong@mail.sic.ac.cn

    2014-10-14

    Relaxation like dielectric anomaly is observed in Y? and Mn? doped barium strontium titanate ceramics when the temperature is over 450 K. Apart from the conventional dielectric relaxation analysis method with Debye or modified Debye equations, which is hard to give exact temperature dependence of the relaxation process, dielectric response in the form of complex impedance, assisted with Cole-Cole impedance model corrected equivalent circuits, is adopted to solve this problem and chase the polarization mechanism in this paper. Through this method, an excellent description to temperature dependence of the dielectric relaxation anomaly and its dominated factors are achieved. Further analysis reveals that the exponential decay of the Cole distribution parameter n with temperature is confirmed to be induced by the microscopic lattice distortion due to ions doping and the interaction between the defects. At last, a clear sight to polarization mechanism containing both the intrinsic dipolar polarization and extrinsic distributed oxygen vacancies hopping response under different temperature is obtained.

  4. High spin polarization in CoFeMnGe equiatomic quaternary Heusler alloy

    SciTech Connect (OSTI)

    Bainsla, Lakhan; Suresh, K. G.; Nigam, A. K.; Manivel Raja, M.; Varaprasad, B. S. D. Ch. S.; Takahashi, Y. K.; Hono, K.

    2014-11-28

    We report the structure, magnetic property, and spin polarization of CoFeMnGe equiatomic quaternary Heusler alloy. The alloy was found to crystallize in the cubic Heusler structure (prototype LiMgPdSn) with considerable amount of DO{sub 3} disorder. Thermal analysis result indicated the Curie temperature is about 750 K without any other phase transformation up to melting temperature. The magnetization value was close to that predicted by the Slater-Pauling curve. Current spin polarization of P = 0.70 ± 0.01 was deduced using point contact andreev reflection measurements. The temperature dependence of electrical resistivity has been fitted in the temperature range of 5–300 K in order to check for the half metallic behavior. Considering the high spin polarization and Curie temperature, this material appears to be promising for spintronic applications.

  5. Structural controlled magnetic anisotropy in Heusler L1{sub 0}-MnGa epitaxial thin films

    SciTech Connect (OSTI)

    Wang Kangkang; Lu Erdong; Smith, Arthur R.; Knepper, Jacob W.; Yang Fengyuan

    2011-04-18

    Ferromagnetic L1{sub 0}-MnGa thin films have been epitaxially grown on GaN, sapphire, and MgO substrates using molecular beam epitaxy. Using diffraction techniques, the epitaxial relationships are determined. It is found that the crystalline orientation of the films differ due to the influence of the substrate. By comparing the magnetic anisotropy to the structural properties, a clear correlation could be established indicating that the in-plane and out-of-plane anisotropy is directly determined by the crystal orientation of the film and could be controlled via selection of the substrates. This result could be helpful in tailoring magnetic anisotropy in thin films for spintronic applications.

  6. Electric field-induced magnetic switching in Mn:ZnO film

    SciTech Connect (OSTI)

    Ren, S. X.; Sun, G. W.; Zhao, J.; Dong, J. Y.; Zhao, X.; Chen, W.; Wei, Y.; Ma, Z. C.

    2014-06-09

    A large magnetic modulation, accompanied by stable bipolar resistive switching (RS) behavior, was observed in a Mn:ZnO film by applying a reversible electric field. A significant enhancement of the ferromagnetism of the film, to about five times larger than that in the initial (as-grown) state (IS), was obtained by switching the film into the low resistance state. X-ray photoelectron spectroscopy demonstrated the existence of abundant oxygen vacancies in the IS of the film. We suggest that this electric field-induced magnetic switching effect originates with the migration and redistribution of oxygen vacancies during RS. Our work indicates that electric switching is an effective and simple method to increase the ferromagnetism of diluted magnetic oxide films. This provides a promising direction for research in spintronic devices.

  7. Characterization of LiMn2O4 cathodes by electrochemical strain microscopy

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Alikin, D. O.; Ievlev, A. V.; Luchkin, S. Yu.; Turygin, A. P.; Shur, V. Ya.; Kalinin, S. V.; Kholkin, A. L.

    2016-03-15

    Electrochemical strain microscopy (ESM) is a scanning probe microscopy(SPM) method in which the local electrodiffusion is probed via application of AC voltage to the SPM tip and registration of resulting electrochemical strain. In this study, we implemented ESM to measure local strain in bulk LiMn2O4 cathodes of a commercial Li-battery in different states of charge to investigate distribution of Li-ion mobility and concentration. Ramped AC ESM imaging and voltage spectroscopy were used to find the most reliable regime of measurements allowing separating and diminishing different contributions to ESM. This is not a trivial task due to complex geometry of themore » sample and various obstacles resulting in less predictable contributions of different origins into ESM response: electrostatic tip–surface interactions, charge injection, electrostriction, and flexoelectricity. Finally, understanding and control of these contributions is an important step towards quantitative interpretation of ESM data.« less

  8. NaNi sub 3 Mn sub 2 alloy as a tritium storage material

    SciTech Connect (OSTI)

    Ide, T.; Okuno, K.; Konishi, S.; Sakai, F.; Fukui, H.; Enoeda, M.; Naruse, Y.; Anderson, J.L.; Bartlit, J.R.; Los Alamos National Lab., NM )

    1989-01-01

    An all metal apparatus has been constructed and installed in the main cell of the Tritium System Assembly (TSTA) at Los Alamos National Laboratory, as a separate experiment, to handle about 2600 Ci of tritium for study of metal tritides of potential application for storing tritium in fusion fuel processing. The apparatus is similar to that used for protium/deuterium gas but some modifications were made to assure safe handling of tritium. The pressure-composition isotherms for the LaNi{sub 3}Mn{sub 2}-protium (H), deuterium (D) and tritium (T) system were measured to study isotopic effects in the temperature range of 60 {degree}C to 250 {degree}C, the pressure range below 120 kPa. 2 refs., 10 figs.

  9. Strain-induced dimensionality crossover of precursor modulations in Ni{sub 2}MnGa

    SciTech Connect (OSTI)

    Nie, Zhihua E-mail: ydwang@neu.edu.cn; Wang, Yandong E-mail: ydwang@neu.edu.cn; Shang, Shunli; Wang, Yi; Liu, Zi-Kui; Zeng, Qiaoshi; Ren, Yang; Liu, Dongmei; Yang, Wenge

    2015-01-12

    Precursor modulations often occur in functional materials like magnetic shape memory alloys, ferroelectrics, and superconductors. In this letter, we have revealed the underlying mechanism of the precursor modulations in ferromagnetic shape memory alloys Ni{sub 2}MnGa by combining synchrotron-based x-ray diffraction experiments and first-principles phonon calculations. We discovered the precursor modulations along [011] direction can be eliminated with [001] uniaxial loading, while the precursor modulations or premartensite can be totally suppressed by hydrostatic pressure condition. The TA{sub 2} phonon anomaly is sensitive to stress induced lattice strain, and the entire TA{sub 2} branch is stabilized along the directions where precursor modulations are eliminated by external stress. Our discovery bridges precursor modulations and phonon anomalies, and sheds light on the microscopic mechanism of the two-step superelasticity in precursor martensite.

  10. Magnetic-field-induced transformation in FeMnGa alloys

    SciTech Connect (OSTI)

    Zhu, W.; Liu, E. K.; Feng, L.; Tang, X. D.; Chen, J. L.; Wu, G. H.; Liu, H. Y.; Meng, F. B.; Luo, H. Z.

    2009-11-30

    A kind of ferromagnetic shape memory alloy with off-stoichiometric composition of Heusler alloy Fe{sub 2}MnGa has been synthesized. By optimizing composition, the martensitic transformation has been modified to occur at about 163 K accompanying spontaneous magnetization, which enables a magnetic field-induced structural transition from a paramagnetic parent phase to a ferromagnetic martensite with high magnetization of 93.8 emu/g. The material performs a quite large lattice distortion through the transformation, (c-a)/c=33.5%, causing a shape memory strain upto 3.6%. Such large lattice distortions strongly influence the electron structures, and thus some special physical behavior related to the transport and conductive properties is investigated.

  11. The manifestation of spin-phonon coupling in CaMnO{sub 3}

    SciTech Connect (OSTI)

    Goian, V. Kamba, S.; Borodavka, F.; Nuzhnyy, D.; Savinov, M.; Belik, A. A.

    2015-04-28

    Recently predicted presence of spin-phonon coupling in the CaMnO{sub 3} is experimentally confirmed in infrared (IR), Raman and time-domain THz spectra. Most of phonon frequencies seen below 350?cm{sup ?1} exhibit significant shifts on cooling below antiferromagnetic phase transition at T{sub N}???120?K. Moreover, several new modes activate in the IR and Raman spectra on cooling below T{sub N}. Sum of phonon contributions to static permittivity exhibits small but reliable anomaly at T{sub N}. On the other hand, the spin-phonon coupling is not manifested in temperature dependence of radio-frequency permittivity, because intrinsic permittivity is screened by extrinsic contribution from conductivity, which enhances the permittivity to giant values.

  12. Magnetic structure and spin excitations in BaMn2Bi2

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Calder, Stuart A.; Saparov, Bayrammurad I; Cao, H. B.; Niedziela, Jennifer L.; Lumsden, Mark D.; Sefat, Athena Safa; Christianson, Andrew D.

    2014-02-19

    We present a single crystal neutron scattering study of BaMn2Bi2, a recently synthesized material with the same ThCr2Si2type structure found in several Fe-based unconventional superconducting materials. We show long range magnetic order, in the form of a G-type antiferromagnetic structure, to exist up to 390 K with an indication of a structural transition at 100 K. Utilizing inelastic neutron scattering we observe a spin-gap of 16 meV, with spin-waves extending up to 55 meV. We find these magnetic excitations are well fit to a J1-J2-Jc Heisenberg model and present values for the exchange interactions. The spin wave spectrum appears tomore » be unchanged by the 100 K structural phase transition.« less

  13. Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr18 FCC solid solution alloy

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Wu, Z.; Bei, H.

    2015-07-01

    Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with amore » composition of FeNiMnCr18 was successfully developed. This near-equiatomic FeNiMnCr18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.« less

  14. Unraveling the voltage fade mechanism in layer Li-Mn-rich electrode: formation of the tetrahedral cations for spinel conversion

    SciTech Connect (OSTI)

    Mohanty, Debasish; Li, Jianlin; Abraham, Daniel P; Huq, Ashfia; Payzant, E Andrew; Wood III, David L; Daniel, Claus

    2014-01-01

    Discovery of high-voltage layered lithium-and manganese-rich (LMR) composite oxide electrode has dramatically enhanced the energy density of current Li-ion energy storage systems. However, practical usage of these materials is currently not viable because of their inability to maintain a consistent voltage profile (voltage fading) during subsequent charge-discharge cycles. This report rationalizes the cause of this voltage fade by providing the evidence of layer to spinel-like (LSL) structural evolution pathways in the host Li1.2Mn0.55Ni0.15Co0.1O2 LMR composite oxide. By employing neutron powder diffraction, and temperature dependent magnetic susceptibility, we show that LSL structural rearrangement in LMR oxide occurs through a tetrahedral cation intermediate via: i) diffusion of lithium atoms from octahedral to tetrahedral sites of the lithium layer [(LiLioct LiLitet] which is followed by the dispersal of the lithium ions from the adjacent octahedral site of the metal layer to the tetrahedral sites of lithium layer [LiTM oct LiLitet]; and ii) migration of Mn from the octahedral sites of the transition metal layer to the permanent octahedral site of lithium layer via tetrahedral site of lithium layer [MnTMoct MnLitet MnLioct)]. The findings opens the door to the potential routes to mitigate this atomic restructuring in the high-voltage LMR composite oxide cathodes by manipulating the composition/structure for practical use in high-energy-density lithium-ion batteries.

  15. Synthesis and characterization of R{sub 2}MnTiO{sub 7} (R = Y and Er) pyrochlores oxides

    SciTech Connect (OSTI)

    Martnez-Coronado, R.; Alonso, J.A.; Fernndez, M.T.

    2013-09-01

    Graphical abstract: - Abstract: New pyrochlore-like phases of composition R{sub 2}MnTiO{sub 7} (R = Er and Y) have been synthesized by a soft-chemistry procedure involving citrates of the different metal ions followed by thermal treatments at moderate temperatures (850 C for 12 h in air). A characterization by X-ray diffraction and neutron powder diffraction (NPD) has been carried out in order to determine the crystal structure features: these phyrochlores are cubic, space group Fd-3m, defining an intrinsically frustrated three-dimensional system. The Rietveld-refinement from NPD data at room temperature evidences an antisite cation disorder (distribution of Mn between A and B positions) that is accompanied by an increment of the oxygen-vacancy concentration due to the reduction of Mn{sup 4+} at the B position to Mn{sup 2+} at the A position. Thermogravimetric analysis (TGA) was useful to evaluate the stability of these oxides in reducing conditions up to 500 C. Magnetic susceptibility measurements indicate a ferromagnetic behavior, due to the random distribution of Mn{sup 4+} ions in the octahedral sublattice. At lower temperatures there is a polarization of the R{sup +3} magnetic moments, which also participate in the magnetic structure. Aiming to evaluate these materials as possible electrodes for solid oxide fuel cells (SOFC) we determined that the thermal expansion coefficients between 100 and 900 C perfectly match with those of the usual electrolytes; however, these pyrochlore oxides display a semiconductor-like behavior with poor conductivity values, e.g. 6 10{sup ?3} cm{sup ?1} at 850 C for Er, which would prevent its use as MIEC (mixed ionic-electronic conductors) oxides in SOFC devices.

  16. First principles treatment of structural, optical, and thermoelectric properties of Li{sub 7}MnN{sub 4} as electrode for a Li secondary battery

    SciTech Connect (OSTI)

    Khan, Wilayat; Reshak, A.H.

    2015-01-15

    The electronic structure, electronic charge density and linear optical properties of the metallic Li{sub 7}MnN{sub 4} compound, having cubic symmetry, are calculated using the full potential linearized augmented plane wave (FP-LAPW) method. The calculated band structure and density of states using the local density, generalized gradient and EngelVosko approximations, depict the metallic nature of the cubic Li{sub 7}MnN{sub 4} compound. The bands crossing the Fermi level in the calculated band structure are mainly from the Mn-d states with small support of N-p states. In addition, the Mn-d states at the Fermi level enhance the density of states, which is very useful for the electronic transport properties. The valence electronic charge density depicts strong covalent bond between Mn and two N atoms and polar covalent bond between Mn and Li atoms. The frequency dependent linear optical properties like real and imaginary part of the dielectric function, optical conductivity, reflectivity and energy loss function are calculated on the basis of the computed band structure. Both intra-band and inter-band transitions contribute to the calculated optical parameters. Using the BoltzTraP code, the thermoelectric properties like electrical and thermal conductivity, Seebeck coefficient, power coefficient and heat capacity of the Li{sub 7}MnN{sub 4} are also calculated as a function of temperature and studied.

  17. The role of the (111) texture on the exchange bias and interlayer coupling effects observed in sputtered NiFe/IrMn/Co trilayers

    SciTech Connect (OSTI)

    Castro, I. L.; Nascimento, V. P.; Passamani, E. C.; Takeuchi, A. Y.; Larica, C.; Tafur, M.; Pelegrini, F.

    2013-05-28

    Magnetic properties of sputtered NiFe/IrMn/Co trilayers grown on different seed layers (Cu or Ta) deposited on Si (100) substrates were investigated by magnetometry and ferromagnetic resonance measurements. Exchange bias effect and magnetic spring behavior have been studied by changing the IrMn thickness. As shown by X-ray diffraction, Ta and Cu seed layers provoke different degrees of (111) fcc-texture that directly affect the exchange bias and indirectly modify the exchange spring coupling behavior. Increasing the IrMn thickness, it was observed that the coupling angle between the Co and NiFe ferromagnetic layers increases for the Cu seed system, but it reduces for the Ta case. The results were explained considering (i) different anisotropies of the Co and IrMn layers induced by the different degree of the (111) texture and (ii) the distinct exchange bias set at the NiFe/IrMn and IrMn/Co interfaces in both systems. The NiFe and Co interlayer coupling angle is strongly correlated with both exchange bias and exchange magnetic spring phenomena. It was also shown that the highest exchange bias field occurs when an unstressed L1{sub 2} IrMn structure is stabilized.

  18. Electrical conductivity anomaly and X-ray photoelectron spectroscopy investigation of YCr{sub 1?x}Mn{sub x}O{sub 3} negative temperature coefficient ceramics

    SciTech Connect (OSTI)

    Zhang, Bo; University of Chinese Academy of Sciences, Beijing 100049 ; Zhao, Qing; Chang, Aimin E-mail: wuy@alfred.edu; Li, Yiyu; Liu, Yin; Wu, Yiquan E-mail: wuy@alfred.edu

    2014-03-10

    Electrical conductivity anomaly of perovskite-type YCr{sub 1?x}Mn{sub x}O{sub 3} negative temperature coefficient (NTC) ceramics produced by spark plasma sintering (SPS) has been investigated by using defect chemistry theory combination with X-ray photoelectron spectroscopy (XPS) analysis. From the results of the ln?-1/T curves and the XPS analysis, it can be considered that YCr{sub 1?x}Mn{sub x}O{sub 3} ceramics exhibit the hopping conductivity. The major carriers in YCrO{sub 3} are holes, which are compensated by the oxygen vacancies produced due to the introduction of Mn ions. The Mn{sup 4+} ion contents increase monotonically in the range of 0.2???x???0.5. The resistivity increases at first and then decreases with increasing Mn contents, which has the same varying tendency with activation energy. The electrical conductivity anomaly appearing in these ceramics may be due to the variation of Cr{sup 4+} and Mn{sup 4+} ions concentration as Mn content changes.

  19. Cd{sub 1−x}Mn{sub x}Te ultrasmall quantum dots growth in a silicate glass matrix by the fusion method

    SciTech Connect (OSTI)

    Dantas, Noelio Oliveira; Lima Fernandes, Guilherme de; Almeida Silva, Anielle Christine; Baffa, Oswaldo; Gómez, Jorge Antônio

    2014-09-29

    In this study, we synthesized Cd{sub 1−x}Mn{sub x}Te ultrasmall quantum dots (USQDs) in SiO{sub 2}-Na{sub 2}CO{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3} glass system using the fusion method. Growth of these Cd{sub 1−x}Mn{sub x}Te USQDs was confirmed by optical absorption, atomic force microscopy (AFM), magnetic force microscopy (MFM), scanning transmission electron microscopy (TEM), and electron paramagnetic resonance (EPR) measurements. The blueshift of absorption transition with increasing manganese concentration gives evidence of incorporation of manganese ions (Mn{sup 2+}) in CdTe USQDs. AFM, TEM, and MFM confirmed, respectively, the formation of high quality Cd{sub 1−x}Mn{sub x}Te USQDs with uniformly distributed size and magnetic phases. Furthermore, EPR spectra showed six lines associated to the S = 5/2 spin half-filled d-state, characteristic of Mn{sup 2+}, and confirmed that Mn{sup 2+} are located in the sites core and surface of the CdTe USQD. Therefore, synthesis of high quality Cd{sub 1−x}Mn{sub x}Te USQDs may allow the control of optical and magnetic properties.

  20. Effect of CoFe insertion in Co{sub 2}MnSi/CoFe/n-GaAs junctions on spin injection properties

    SciTech Connect (OSTI)

    Ebina, Yuya; Akiho, Takafumi; Liu, Hong-xi; Yamamoto, Masafumi; Uemura, Tetsuya

    2014-04-28

    The CoFe thickness (t{sub CoFe}) dependence of spin injection efficiency was investigated for Co{sub 2}MnSi/CoFe/n-GaAs junctions. The ?V{sub NL}/I value, which is a measure of spin injection efficiency, strongly depended on t{sub CoFe}, where ?V{sub NL} is the amplitude of a nonlocal spin-valve signal, and I is an injection current. Importantly, the maximum value of ?V{sub NL}/I for a Co{sub 2}MnSi/CoFe/n-GaAs junction was one order of magnitude higher than that for a CoFe/n-GaAs junction, indicating that a Co{sub 2}MnSi electrode works as a highly polarized spin source. No clear spin signal, on the other hand, was observed for a Co{sub 2}MnSi/n-GaAs junction due to diffusion of Mn atoms into the GaAs channel. Secondary ion mass spectrometry analysis indicated that the CoFe insertion effectively suppressed the diffusion of Mn into GaAs, resulting in improved spin injection properties compared with those for a Co{sub 2}MnSi/n-GaAs junction.

  1. The effect of Ca-substitution in La-site on the magnetic properties of La{sub 2}CoMnO{sub 6}

    SciTech Connect (OSTI)

    Li, Qiu-hang; Li, Na; Hu, Jian-zhong; Han, Qi; Ma, Qing-shan; Ge, Lei; Xiao, Biao; Xu, Ming-xiang

    2014-07-21

    Double perovskite La{sub 2-x}Ca{sub x}CoMnO{sub 6} (x?=?0, 0.1, 0.2, 0.5) ceramics samples were synthesized by the standard solid-state reaction method. The crystal structures have been confirmed to be monoclinic perovskite structure with space group of P2{sub 1}/n at room temperature by the powder x-ray diffraction (Cu-K?). The grains of the samples are relatively dense and distribute in random directions from the scanning electron microscope patterns. Holes are doped into La{sub 2}CoMnO{sub 6} with the substitution of the Ca{sup 2+} ions in La-site, and further lead to the valences of Mn ions and Co ions transforming from Mn{sup 4+} and Co{sup 2+} to Mn{sup 3+} and Co{sup 3+}, respectively. Ferromagnetic coupling of Mn{sup 4+}-O{sup 2}-Co{sup 2+} and antiferromagnetic coupling of Mn{sup 3+}-O{sup 2}-Co{sup 3+} are coexistent in La{sub 2-x}Ca{sub x}CoMnO{sub 6} system, which correspond to two transitions existed in field-cooling magnetization versus temperature curves. Curie temperature of La{sub 2-x}Ca{sub x}CoMnO{sub 6} system decreases with the increasing of Ca-substitution amount. The coexistence of different magnetic phases leads to the exchange bias effect.

  2. Effect of L1{sub 2} ordering in antiferromagnetic Ir-Mn epitaxial layer on exchange bias of FePd films

    SciTech Connect (OSTI)

    Chang, Y. C.; Duh, J. G. E-mail: lin.yg@nsrrc.org.tw; Hsiao, S. N. E-mail: lin.yg@nsrrc.org.tw; Liu, S. H.; Su, S. H.; Chiu, K. F.; Hsieh, W. C.; Chen, S. K.; Lin, Y. G. E-mail: lin.yg@nsrrc.org.tw; Lee, H. Y.; Sung, C. K.

    2015-05-07

    Two series of samples of single-layer IrMn and IrMn/FePd bilayer films, deposited on a single-crystal MgO substrate at different IrMn deposition temperatures (T{sub s} = 300–700 °C), were investigated using magnetron sputtering. L1{sub 2} ordering was revealed for the 30 nm-thick IrMn epitaxial (001) films with T{sub s} ≥ 400 °C, determined by synchrotron radiation x-ray diffractometry (XRD). XRD results also provide evidence of the epitaxial growth of the IrMn films on MgO substrate. Increasing T{sub s} from 400 to 700 °C monotonically increases the ordering parameter of L1{sub 2} phases from 0.17 to 0.81. An in-plane exchange bias field (H{sub eb}) of 22 Oe is obtained in a 10 nm-thick FePd film that is deposited on the disordered IrMn films. As the L1{sub 2} ordering of the IrMn layers increases, the H{sub eb} gradually decreases to 0 Oe, meaning that the exchange bias behavior vanishes. The increased surface roughness, revealed by atomic force microscopy, of the epitaxial IrMn layers with increasing T{sub s} cannot be the main cause of the decrease in H{sub eb} due to the compensated surface spins regardless of the disordered and ordered (001) IrMn layers. The change of antiferromagnetic structure from the A1 to the L1{sub 2} phase was correlated with the evolution of H{sub eb}.

  3. Synthesis of murdochite-type Ni{sub 6}MnO{sub 8} with variable specific surface areas and the application in methane oxidation

    SciTech Connect (OSTI)

    Taguchi, Hideki; Tahara, Shohei; Okumura, Mikoto; Hirota, Ken

    2014-07-01

    To synthesize a murdochite-type Ni{sub 6}MnO{sub 8} with variable specific surface areas, an oxalate precursor was calcined at 350500 C in flowing argon, and the calcined sample was heated to 600 C in air. The lattice constant of the Ni{sub 6}MnO{sub 8} did not depend on the calcination temperature of the precursor, while the specific surface area decreased from 8.4 m{sup 2}/g to 2.6 m{sup 2}/g when increasing the calcination temperature of the precursor. The methane (CH{sub 4}) oxidation data indicated that the temperature corresponding to the 50% conversion (T{sub 50%}) of Ni{sub 6}MnO{sub 8} calcined at 350 C or 400 C was lower than that of all other Ni{sub 6}MnO{sub 8} specimens. However, the intrinsic conversion of Ni{sub 6}MnO{sub 8} calcined at 350 C, which is defined as conversion per specific surface area, was half of that of all other Ni{sub 6}MnO{sub 8} specimens. The degree of crystallinity and catalytic performance of the Ni{sub 6}MnO{sub 8} calcined at 400 C were high. - Graphical abstract: The conversion of CH{sub 4} into CO{sub 2} and H{sub 2}O on Ni{sub 6}MnO{sub 8}, which was heated at 600 C in air after the calcination of the precursor at 350 C, 400 C, 450 C, or 500 C in flowing argon, was measured. Since the specific surface area was strongly affected by the calcination temperature of the precursor, intrinsic conversion (IC) was defined as conversion per the specific surface area. For comparison, the IC value on Ni{sub 6}MnO{sub 8} synthesized by the direct calcination of the precursor at 600 C in air is plotted. - Highlights: The oxalate precursor was calcined at 350500 C in flowing argon. Murdochite-type Ni{sub 6}MnO{sub 8} was obtained by heating the calcined sample in air. The specific surface area of Ni{sub 6}MnO{sub 8} varied with the calcination temperature. The degree of crystallinity and catalysis of Ni{sub 6}MnO{sub 8} calcined at 400 C were high.

  4. Strong room-temperature ferromagnetism of high-quality lightly Mn-doped ZnO grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Zuo Zheng; Zhou Huimei; Olmedo, Mario J.; Kong Jieying; Liu Jianlin; Beyermann, Ward P.; Zheng Jianguo; Xin Yan

    2012-09-01

    Strong room-temperature ferromagnetism is demonstrated in single crystalline Mn-doped ZnO grown by molecular beam epitaxy. With a low Mn concentration of 2 Multiplication-Sign 10{sup 19} cm{sup -3}, Mn-doped ZnO films exhibited room-temperature ferromagnetism with a coercivity field larger than 200 Oe, a large saturation moment of 6 {mu}{sub B}/ion, and a large residue moment that is {approx}70% of the saturation magnetization. Isolated ions with long range carrier mediated spin-spin coupling may be responsible for the intrinsic ferromagnetism.

  5. In-plane tunneling anisotropic magnetoresistance in (Ga,Mn)As/GaAs Esaki diodes in the regime of the excess current

    SciTech Connect (OSTI)

    Shiogai, J.; Ciorga, M. Utz, M.; Schuh, D.; Bougeard, D.; Weiss, D.; Kohda, M.; Nitta, J.; Nojima, T.

    2015-06-29

    We investigate the angular dependence of the tunneling anisotropic magnetoresistance in (Ga,Mn)As/n-GaAs spin Esaki diodes in the regime where the tunneling process is dominated by the excess current through midgap states in (Ga,Mn)As. We compare it to similar measurements performed in the regime of band-to-band tunneling. Whereas the latter show biaxial symmetry typical for magnetic anisotropy observed in (Ga,Mn)As samples, the former is dominated by uniaxial anisotropy along the 〈110〉 axes.

  6. Atomic moments in Mn2CoAl thin films analyzed by X-ray magnetic circular dichroism

    SciTech Connect (OSTI)

    Jamer, M.; Sterbinsky, G.; Assaf, B.; Arena, D.; Heiman, D.

    2014-12-05

    Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. The results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value. (auth)

  7. Atomic moments in Mn2CoAl thin films analyzed by X-ray magnetic circular dichroism

    SciTech Connect (OSTI)

    Jamer, M. E.; Assaf, B. A.; Sterbinsky, G. E.; Arena, D. A.; Heiman, D.

    2014-12-05

    Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. Results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value.

  8. Magneto-transport in LaTi{sub 1−x}Mn{sub x}O{sub 3}/SrTiO{sub 3} oxide heterostructures

    SciTech Connect (OSTI)

    Kumar, Pramod Dogra, Anjana Budhani, R. C.

    2014-04-24

    We report the growth of ultrathin film of Mn doped LaTiO{sub 3} on TiO{sub 2} terminated SrTiO{sub 3} (001) substrate by pulsed laser deposition (PLD) and their electrical transport characteristics including magnetoresistance (MR). Though the replacement of Mn in LaTiO{sub 3} at the Ti site in dilute limit does not affect the metallic behaviour of films but variation in resistance is observed. Normalised resistance behaviour is explained on the basis of variation in charge carriers and increased interaction between Mn atoms in the system under investigation.

  9. Sign Reversal of the MN-O Bond Compressibility in La{sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7} Below T{sub C}: Exchange Striction in the Ferromagnetic State

    DOE R&D Accomplishments [OSTI]

    Argyriou, D. N.; Mitchell, J. F.; Chmaissem, O.; Short, S.; Jorgensen, J. D.; Goodenough, J. B.

    1997-03-01

    The crystal structure of the layered perovskite La{sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7} has been studied under hydrostatic pressure up to {approximately} 6 kbar, in the paramagnetic and ferromagnetic states, with neutron powder diffraction. The compressibility of the Mn-O apical bonds in the double layer of MnO{sub 6} octahedra changes sign from the paramagnetic insulator (PI) to the ferromagnetic metal (FM) state; in the Fm state the Mn-O-Mn linkage between MnO{sub 2} planes expands under applied pressure, whereas they contract in the PI state. This counterintuative behavior is interpreted in terms of exchange striction, which reflect the competition between super- and double-exchange. An increase of the Mn-moment with applied pressure in the FM state is consistent with a positive dT{sub C}/dP, as well as a cant angle {theta}{sub 0} between the magnetizations of neighboring MnO{sub 2} sheets that decreases with pressure.

  10. Magnetic Transitions in the Spin-5/2 Frustrated Magnet BiMn2PO6 and Strong Lattice Softening in BiMn2PO6 and BiZn2PO6 Below 200 K

    SciTech Connect (OSTI)

    Nath, R; Ranjith, K M; Roy, B; Johnston, D C; Furukawa, Y; Tsirlin, A A

    2014-07-01

    The crystallographic, magnetic, and thermal properties of polycrystalline BiMn2PO6 and its nonmagnetic analog BiZn2PO6 are investigated by x-ray diffraction, magnetization M, magnetic susceptibility ?, heat capacity Cp, and P31 nuclear magnetic resonance (NMR) measurements versus applied magnetic field H and temperature T as well as by density-functional band theory and molecular-field calculations. Both compounds show a strong monotonic lattice softening on cooling, where the Debye temperature decreases by a factor of two from ?D?650 K at T=300 K to ?D?300 K at T=2 K. The ?(T) data for BiMn2PO6 above 150 K follow a Curie-Weiss law with a Curie constant consistent with a Mn+2 spin S=5/2 with g factor g=2 and an antiferromagnetic (AFM) Weiss temperature ?CW??78 K. The ? data indicate long-range AFM ordering below TN?30 K, confirmed by a sharp ?-shaped peak in Cp(T) at 28.8 K. The magnetic entropy at 100 K extracted from the Cp(T) data is consistent with spin S=5/2 for the Mn+2 cations. The band-theory calculations indicate that BiMn2PO6 is an AFM compound with dominant interactions J1/kB?6.7 K and J3/kB?5.6 K along the legs and rungs of a Mn two-leg spin-ladder, respectively. However, sizable and partially frustrating interladder couplings lead to an anisotropic three-dimensional magnetic behavior with long-range AFM ordering at TN?30 K observed in the ?, Cp, and NMR measurements. A second magnetic transition at ?10 K is observed from the ? and NMR measurements but is not evident in the Cp data. The Cp data at low T suggest a significant contribution from AFM spin waves moving in three dimensions and the absence of a spin-wave gap. A detailed analysis of the NMR spectra indicates commensurate magnetic order between 10 and 30 K, while below 10 K additional features appear that may arise from an incommensurate modulation and/or spin canting. The commensurate order is consistent with microscopic density functional calculations that yield a collinear Nel-type AFM spin

  11. Enhance D. C. resistivity of Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} ceramic by acceptor (Mn) doping

    SciTech Connect (OSTI)

    Sharma, Hakikat Arya, G. S.; Pramar, Kusum; Negi, N. S.

    2015-05-15

    In the present work, we prepared Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and Mn (2 and 3 at % on Ti site) doped Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} ceramic by sol- gel method. The samples were characterized by X-ray diffraction (XRD). The XRD patterns reveled that Mn ions did not change the perovskite structure of BST (70/30). The dielectric measurements proved that dielectric constant decreased with Mn doping. The dc resistivity was studied by using I-V measurements. The dc resistivity of the BST increased with Mn doping, which suppressed the leakage current.

  12. Properties of molecular beam epitaxy grown Eu{sub x}(transition metal){sub y} films (transition metals: Mn, Cr)

    SciTech Connect (OSTI)

    Balin, K.; Nowak, A.; Gibaud, A.; Szade, J.; Celinski, Z.

    2011-04-01

    The electronic and crystallographic structures, as well as the magnetic properties, of Eu{sub x}(transition metal){sub y} (transition metals: Mn, Cr) thin films grown by molecular beam epitaxy were studied. Relative changes of the Eu/Mn and Eu/Cr ratios derived from the XPS lines, as well as x-ray reflectivity, indicate mixing of the Eu/Mn and Eu/Cr layers. Valency transitions from Eu{sup 2+} to Eu{sup 3+} were observed in both systems for most studied stoichiometries. A transition to a magnetically ordered phase was observed at 15 K, 40 K, and 62 K for selected films in the Eu-Mn system, and at 50 K for the film with a Eu/Cr ratio of 0.5.

  13. Bicolor Mn-doped CuInS{sub 2}/ZnS core/shell nanocrystals for white light-emitting diode with high color rendering index

    SciTech Connect (OSTI)

    Huang, Bo; Dai, Qian; Zhang, Huichao; Liao, Chen; Cui, Yiping; Zhang, Jiayu; Zhuo, Ningze; Jiang, Qingsong; Shi, Fenghua; Wang, Haibo

    2014-09-07

    We synthesized bicolor Mn-doped CuInS{sub 2} (CIS)/ZnS core/shell nanocrystals (NCs), in which Mn{sup 2+} ions and the CIS core were separated with a ZnS layer, and both Mn{sup 2+} ions and CIS cores could emit simultaneously. Transmission electron microscopy and powder X-ray diffraction measurements indicated the epitaxial growth of ZnS shell on the CuInS{sub 2} core, and electron paramagnetic resonance spectrum indicated that Mn{sup 2+} ions were on the lattice points of ZnS shell. By integrating these bicolor NCs with commercial InGaN-based blue-emitting diodes, tricolor white light-emitting diodes with color rendering index of 83 were obtained.

  14. The effects of high magnetic field on the morphology and microwave electromagnetic properties of MnO{sub 2} powder

    SciTech Connect (OSTI)

    Jia Zhang [Department of Materials Processing Engineering, School of Materials Science and Engineering, Dalian University of Technology, Linggong Road 2, Ganjingzi District, Dalian 116085, Liaoning Province (China); Duan Yuping, E-mail: duanyp@dlut.edu.c [Department of Materials Processing Engineering, School of Materials Science and Engineering, Dalian University of Technology, Linggong Road 2, Ganjingzi District, Dalian 116085, Liaoning Province (China); Li Shuqing, E-mail: lsq6668@126.co [Beijing Aeronautical Manufacturing Technology Research Institute, 1 Jun Zhuang east Road, Chaoyang District, Beijing 100024 (China); Li Xiaogang, E-mail: lixiaogang99@263.ne [School of Materials Science and Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083 (China); Liu Shunhua [Department of Materials Processing Engineering, School of Materials Science and Engineering, Dalian University of Technology, Linggong Road 2, Ganjingzi District, Dalian 116085, Liaoning Province (China)

    2010-07-15

    MnO{sub 2} with a sea urchin-like ball chain shape was first synthesized in a high magnetic field via a simple chemical process, and a mechanism for the formation of this grain shape was discussed. The as-synthesized samples were characterized by XRD, SEM, TEM, and vector network analysis. The dielectric constant and the loss tangent clearly decreased under a magnetic field. The magnetic loss tangent and the imaginary part of the magnetic permeability increased substantially. Furthermore, the theoretically calculated values of reflection loss showed that the absorption peaks shifted to a higher frequency with increases in the magnetic field strength. - Graphical abstract: MnO{sub 2} with a sea urchin-like ball chain shape is first synthesized in a high magnetic field via a simple hydrothermal route.

  15. Epitaxial Mn{sub 2.5}Ga thin films with giant perpendicular magnetic anisotropy for spintronic devices

    SciTech Connect (OSTI)

    Wu Feng; Mizukami, Shigemi; Watanabe, Daisuke; Miyazaki, Terunobu; Naganuma, Hiroshi; Oogane, Mikihiko; Ando, Yasuo

    2009-03-23

    We report on epitaxial growth and magnetic properties of Mn{sub 2.5}Ga thin films, which were deposited on Cr/MgO single crystal substrates by magnetron sputtering. X-ray diffraction results revealed the epitaxial relationships as Mn{sub 2.5}Ga(001)[100] parallel Cr(001)[110] parallel MgO(001)[100]. The presence of (002) and (011) superlattice peaks indicates that the films were crystallized into DO{sub 22} ordered structures. The perpendicular magnetic anisotropy (PMA) properties were found to be related to the extent of DO{sub 22} chemical ordering. A giant PMA (K{sub u}{sup eff}=1.2x10{sup 7} erg/cm{sup 3}) and low saturation magnetization (M{sub s}=250 emu/cm{sup 3}) can be obtained for the film with highest chemical ordering parameter (S=0.8)

  16. Conditions for spin-gapless semiconducting behavior in Mn{sub 2}CoAl inverse Heusler compound

    SciTech Connect (OSTI)

    Galanakis, I.; zdo?an, K.; ?a??o?lu, E.; Blgel, S.

    2014-03-07

    Employing ab initio electronic structure calculations, we investigate the conditions for spin-gapless semiconducting (SGS) behavior in the inverse Mn{sub 2}CoAl Heusler compound. We show that tetragonalization of the lattice, which can occur during films growth, keeps the SGS character of the perfect cubic compound. On the contrary, atomic swaps even between sites with different local symmetry destroy the SGS character giving rise to a half-metallic state. Furthermore, the occurrence of Co-surplus leads also to half-metallicity. Thus, we propose that in order to achieve SGS behavior during the growth of Mn{sub 2}CoAl (and similar SGS Heusler compounds) thin films, one should minimize the occurrence of defects, while small deformations of the lattice, due to the lattice mismatch with the substrate, do not play a crucial role.

  17. Alternating magnetic anisotropy of Li2(Li1–xTx)N (T = Mn, Fe, Co, and Ni)

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Jesche, A.; Ke, L.; Jacobs, J. L.; Harmon, B.; Houk, R. S.; Canfield, P. C.

    2015-05-11

    Substantial amounts of the transition metals Mn, Fe, Co, and Ni can be substituted for Li in single crystalline Li2(Li1–xTx)N. Isothermal and temperature-dependent magnetization measurements reveal local magnetic moments with magnitudes significantly exceeding the spin-only value. The additional contributions stem from unquenched orbital moments that lead to rare-earth-like behavior of the magnetic properties. Accordingly, extremely large magnetic anisotropies have been found. Most notably, the magnetic anisotropy alternates as easy plane→easy axis→easy plane→easy axis when progressing from T = Mn → Fe → Co → Ni. This behavior can be understood based on a perturbation approach in an analytical, single-ion model.more » As a result, the calculated magnetic anisotropies show surprisingly good agreement with the experiment and capture the basic features observed for the different transition metals.« less

  18. Intrinsic quantum anomalous Hall effect in the kagome lattice Cs2LiMn3F12

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Xu, Gang; Lian, Biao; Zhang, Shou -Cheng

    2015-10-27

    In a kagome lattice, the time reversal symmetry can be broken by a staggered magnetic flux emerging from ferromagnetic ordering and intrinsic spin-orbit coupling, leading to several well-separated nontrivial Chern bands and intrinsic quantum anomalous Hall effect. Based on this idea and ab initio calculations, we propose the realization of the intrinsic quantum anomalous Hall effect in the single layer Cs2Mn3F12 kagome lattice and on the (001) surface of a Cs2LiMn3F12 single crystal by modifying the carrier coverage on it, where the band gap is around 20 meV. Furthermore, a simplified tight binding model based on the in-plane ddσ antibondingmore » states is constructed to understand the topological band structures of the system.« less

  19. Alternating magnetic anisotropy of Li 2 ( Li 1 - x T x ) N ( T = Mn , Fe , Co , and Ni )

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Jesche, A.; Ke, L.; Jacobs, J. L.; Harmon, B.; Houk, R. S.; Canfield, P. C.

    2015-05-01

    Substantial amounts of the transition metals Mn, Fe, Co, and Ni can be substituted for Li in single crystalline Li?(Li1-xTx)N. Isothermal and temperature-dependent magnetization measurements reveal local magnetic moments with magnitudes significantly exceeding the spin-only value. The additional contributions stem from unquenched orbital moments that lead to rare-earth-like behavior of the magnetic properties. Accordingly, extremely large magnetic anisotropies have been found. Most notably, the magnetic anisotropy alternates as easy plane?easy axis?easy plane?easy axis when progressing from T = Mn ? Fe ? Co ? Ni. This behavior can be understood based on a perturbation approach in an analytical, single-ion model.moreThe calculated magnetic anisotropies show surprisingly good agreement with the experiment and capture the basic features observed for the different transition metals.less

  20. Annealing effects on the structural and magnetic properties of off-stoichiometric Fe-Mn-Ga ferromagnetic shape memory alloys

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Chen, Yan; Bei, Hongbin; Dela Cruz, Clarina R; Wang, Yandong; An, Ke

    2016-05-07

    Annealing plays an important role in modifying structures and properties of ferromagnetic shape memory alloys (FSMAs). The annealing effect on the structures and magnetic properties of off-stoichiometric Fe45Mn26Ga29 FSMA has been investigated at different elevated temperatures. Rietveld refinements of neutron diffraction patterns display that the formation of the γ phase in Fe45Mn26Ga29 annealed at 1073 K increases the martensitic transformation temperature and reduces the thermal hysteresis in comparison to the homogenized sample. The phase segregation of a Fe-rich cubic phase and a Ga-rich cubic phase occurs at the annealing temperature of 773 K. The atomic occupancies of the alloys aremore » determined thanks to the neutron's capability of differentiating transition metals. The annealing effects at different temperatures introduce a different magnetic characteristic that is associated with distinctive structural changes in the crystal.« less

  1. Metallic transport and large anomalous Hall effect at room temperature in ferrimagnetic Mn{sub 4}N epitaxial thin film

    SciTech Connect (OSTI)

    Shen, Xi; Shigematsu, Kei; Chikamatsu, Akira Fukumura, Tomoteru; Hirose, Yasushi; Hasegawa, Tetsuya

    2014-08-18

    We report the electrical transport properties of ferrimagnetic Mn{sub 4}N (001) epitaxial thin films grown by pulsed laser deposition on MgO (001) substrates. The Mn{sub 4}N thin films were tetragonally distorted with a ratio of out-of-plane to in-plane lattice constants of 0.987 and showed perpendicular magnetic anisotropy with an effective magnetic anisotropy constant of 0.16 MJ/m{sup 3}, which is comparable with that of a recently reported molecular-beam-epitaxy-grown film. The thin films exhibited metallic transport with a room temperature resistivity of 125 μΩ cm in addition to a large anomalous Hall effect with a Hall angle tangent of 0.023.

  2. Giant spontaneous Hall effect in zero-moment Mn{sub 2}Ru{sub x}Ga

    SciTech Connect (OSTI)

    Thiyagarajah, Naganivetha; Lau, Yong-Chang; Betto, Davide; Borisov, Kiril; Coey, J. M. D.; Stamenov, Plamen; Rode, Karsten

    2015-03-23

    Spin-dependent transport properties of Mn{sub 2}Ru{sub x}Ga thin-films are studied as function of the Ru concentration and the substrate-induced strain. The large spontaneous Hall angle of 7.7% twenty times bigger than in other 3d metals is a signature of its half-metallicity. The compensation temperature where the magnetization of the two inequivalent antiferromagnetically coupled Mn sublattices cancel can be tuned by varying x or the biaxial strain. This zero-moment half metal is free from demagnetizing forces and creates no stray field, effectively removing two obstacles to integrating magnetic elements in densely packed, nanometer-scale memory elements, and millimeter-wave generators.

  3. Enhanced magnetic hysteresis in Ni-Mn-Ga single crystal and its influence on magnetic shape memory effect

    SciTech Connect (OSTI)

    Heczko, O. Drahokoupil, J.; Straka, L.

    2015-05-07

    Enhanced magnetic hysteresis due to boron doping in combination with magnetic shape memory effect in Ni-Mn-Ga single crystal results in new interesting functionality of magnetic shape memory (MSM) alloys such as mechanical demagnetization. In Ni{sub 50.0}Mn{sub 28.5}Ga{sub 21.5} single crystal, the boron doping increased magnetic coercivity from few Oe to 270?Oe while not affecting the transformation behavior and 10?M martensite structure. However, the magnetic field needed for MSM effect also increased in doped sample. The magnetic behavior is compared to undoped single crystal of similar composition. The evidence from the X-ray diffraction, magnetic domain structure, magnetization loops, and temperature evolution of the magnetic coercivity points out that the enhanced hysteresis is caused by stress-induced anisotropy.

  4. Extended investigation of intermartensitic transitions in Ni-Mn-Ga magnetic shape memory alloys: A detailed phase diagram determination

    SciTech Connect (OSTI)

    akir, Asli; Aktrk, Seluk; Righi, Lara

    2013-11-14

    Martensitic transitions in shape memory Ni-Mn-Ga Heusler alloys take place between a high temperature austenite and a low temperature martensite phase. However, intermartensitic transformations have also been encountered that occur from one martensite phase to another. To examine intermartensitic transitions in magnetic shape memory alloys in detail, we carried out temperature dependent magnetization, resistivity, and x-ray diffraction measurements to investigate the intermartensitic transition in Ni{sub 50}Mn{sub 50x}Ga{sub x} in the composition range 12?x?25 at. %. Rietveld refined x-ray diffraction results are found to be consistent with magnetization and resistivity data. Depending on composition, we observe that intermartensitic transitions occur in the sequences 7M?L1{sub 0},?5M?7M, and 5M?7M?L1{sub 0} with decreasing temperature. The L1{sub 0} non-modulated structure is most stable at low temperature.

  5. Magneto-transport properties of oriented Mn{sub 2}CoAl films sputtered on thermally oxidized Si substrates

    SciTech Connect (OSTI)

    Xu, G. Z.; Du, Y.; Zhang, X. M.; Liu, E. K.; Wang, W. H. Wu, G. H.; Zhang, H. G.

    2014-06-16

    Spin gapless semiconductors are interesting family of materials by embracing both magnetism and semiconducting due to their unique band structure. Its potential application in future spintronics requires realization in thin film form. In this Letter, we report fabrication and transport properties of spin gapless Mn{sub 2}CoAl films prepared on thermally oxidized Si substrates by magnetron sputtering deposition. The films deposited at 673 K are well oriented to (001) direction and display a uniform-crystalline surface. Magnetotransport measurements on the oriented films reveal a semiconducting-like resistivity, small anomalous Hall conductivity, and linear magnetoresistance representative of the transport signatures of spin gapless semiconductors. The magnetic properties of the films have also been investigated and compared to that of bulk Mn{sub 2}CoAl, showing small discrepancy induced by the composition deviation.

  6. Alternating magnetic anisotropy of Li2(Li1xTx)N(T=Mn,Fe,Co,andNi)

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Jesche, A.; Ke, L.; Jacobs, J. L.; Harmon, B.; Houk, R. S.; Canfield, P. C.

    2015-05-11

    Substantial amounts of the transition metals Mn, Fe, Co, and Ni can be substituted for Li in single crystalline Li2(Li1xTx)N. Isothermal and temperature-dependent magnetization measurements reveal local magnetic moments with magnitudes significantly exceeding the spin-only value. The additional contributions stem from unquenched orbital moments that lead to rare-earth-like behavior of the magnetic properties. Accordingly, extremely large magnetic anisotropies have been found. Most notably, the magnetic anisotropy alternates as easy plane?easy axis?easy plane?easy axis when progressing from T = Mn ? Fe ? Co ? Ni. This behavior can be understood based on a perturbation approach in an analytical, single-ion model.moreAs a result, the calculated magnetic anisotropies show surprisingly good agreement with the experiment and capture the basic features observed for the different transition metals.less

  7. Temperature-induced martensite in magnetic shape memory Fe{sub 2}MnGa observed by photoemission electron microscopy

    SciTech Connect (OSTI)

    Jenkins, Catherine; Scholl, Andreas; Kainuma, R.; Elmers, Hans-Joachim; Omori, Toshihiro

    2012-01-18

    The magnetic domain structure in single crystals of a Heusler shape memory compound near the composition Fe{sub 2}MnGa was observed during phase transition by photoelectron emission microscopy at Beamline 11.0.1.1 of the Advanced Light Source. The behavior is comparable with recent observations of an adaptive martensite phase in prototype Ni{sub 2}MnGa, although the pinning in the recent work is an epitaxial interface and in this work the e#11;ective pinning plane is a boundary between martensitic variants that transform in a self-accommodating way from the single crystal austenite phase present at high temperatures. Temperature dependent observations of the twinning structure give information as to the coupling behavior between the magnetism and the structural evolution.

  8. Solvothermal synthesis of Zn{sub 2}GeO{sub 4}:Mn{sup 2+} nanophosphor in water/diethylene glycol system

    SciTech Connect (OSTI)

    Takeshita, Satoru; Honda, Joji; Isobe, Tetsuhiko; Sawayama, Tomohiro; Niikura, Seiji

    2012-05-15

    The influence of aging of the suspension containing the amorphous precusors on structural, compositional and photoluminescent properties is studied to understand the mechanism on the formation of Zn{sub 2}GeO{sub 4}:Mn{sup 2+} nanoparticles during the solvothermal reaction in the water/diethylene glycol mixed solvent. Aging at 200 Degree-Sign C for 20 min forms the crystalline Zn{sub 2}GeO{sub 4} nanorods and then they grow up to {approx} 50 nm in mean length after aging for 240 min. Their interplanar spacing of (410) increases with increasing the aging time. The photoluminescence intensity corresponding to the d-d transition of Mn{sup 2+} increases with increasing the aging time up to 120 min, and then decreases after aging for 240 min. The photoluminescence lifetime decreases with increasing the aging time, indicating the locally concentrated Mn{sup 2+} ions. These results reveal that Mn{sup 2+} ions gradually replace Zn{sup 2+} ions near surface through repeating dissolusion and precipitation processes during prolonged aging after the complete crystallization of Zn{sub 2}GeO{sub 4}. - Graphical abstract: TEM images of Zn{sub 2}GeO{sub 4}:Mn{sup 2+} nanoparticles aged at 200 Degree-Sign C for different aging times in the mixed solvent of water and diethylene glycol. Highlights: Black-Right-Pointing-Pointer Mechanism on formation of Zn{sub 2}GeO{sub 4}:Mn{sup 2+} nanophosphor under solvothermal condition. Black-Right-Pointing-Pointer Zn{sub 2}GeO{sub 4} nanorods crystallize via amorphous precursors. Black-Right-Pointing-Pointer Gradual substitution of Mn{sup 2+} during prolonged aging. Black-Right-Pointing-Pointer Such an inhomogeneous Mn{sup 2+} doping process results in concentration quenching.

  9. Characterization of precipitation behaviors in a non-stoichiometric Cu-24.5at.%Al-19.4at.%Mn alloy

    SciTech Connect (OSTI)

    Jeng, S.C.

    2011-02-15

    Scanning and transmission electron microscopy examinations of Cu-24.5at.% Al-19.4at.%Mn (similar to Cu{sub 2.2}Mn{sub 0.8}Al) alloy were performed after aging at temperatures ranging from 350 deg. C to 700 deg. C for various durations. It was observed that only {gamma}-brass type and L-J phases were formed after aging at or below 400 deg. C. On the other hand, the {beta}-Mn phase was formed after aging at temperatures ranging from 500 deg. C to 650 deg. C. It is noteworthy that the precipitation behaviors of the {gamma}-brass type and {beta}-Mn phases are different at different aging temperatures. This remarkable result differs from those reported in previous studies on the Cu{sub 3-X}Mn{sub X}Al alloys with X {<=} 1. - Research Highlights: {yields}Precipitation behaviors in a Cu{sub 2.2}Mn{sub 0.8}Al alloy shows different results from those reported in previous studies on the Cu-A-lMn alloys. {yields}The {gamma}-brass type precipitate occurs at temperatures ranging from 350 deg. C to 500 deg. C revealing different precipitation characteristics. {yields}The {beta}-Mn phase formed after aging at 500 deg. C to 650 deg. C shows different precipitation behaviors as well. {yields}L-J phase having an orthorhombic structure could be always observed in the as-quenched and aged conditions.

  10. Role of W and Mn for reliable 1X nanometer-node ultra-large-scale integration Cu interconnects proved by atom probe tomography

    SciTech Connect (OSTI)

    Shima, K.; Shimizu, H.; Momose, T.; Shimogaki, Y.; Tu, Y.; Takamizawa, H.; Shimizu, Y.; Inoue, K.; Nagai, Y.

    2014-09-29

    We used atom probe tomography (APT) to study the use of a Cu(Mn) as a seed layer of Cu, and a Co(W) single-layer as reliable Cu diffusion barriers for future interconnects in ultra-large-scale integration. The use of Co(W) layer enhances adhesion of Cu to prevent electromigration and stress-induced voiding failures. The use of Cu(Mn) as seed layer may enhance the diffusion barrier performance of Co(W) by stuffing the Cu diffusion pass with Mn. APT was used to visualize the distribution of W and Mn in three dimensions with sub-nanometer resolution. W was found to segregate at the grain boundaries of Co, which prevents diffusion of Cu via the grain boundaries. Mn was found to diffuse from the Cu(Mn) layer to Co(W) layer and selectively segregate at the Co(W) grain boundaries with W, reinforcing the barrier properties of Co(W) layer. Hence, a Co(W) barrier coupled with a Cu(Mn) seed layer can form a sufficient diffusion barrier with film that is less than 2.0-nm-thick. The diffusion barrier behavior was preserved following a 1-h annealing at 400 °C. The underlayer of the Cu interconnects requires a large adhesion strength with the Cu, as well as low electrical resistivity. The use of Co(W) has previously been shown to satisfy these requirements, and addition of Mn is not expected to deteriorate these properties.

  11. Structural, morphological, and magnetic characterization of In{sub 1-x}Mn{sub x}As quantum dots grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Ferri, F. A.; Marega, E. Jr.; Coelho, L. N.; Kunets, V. P.; Salamo, G. J.

    2012-08-01

    In this paper, we present a method to order low temperature (LT) self-assembled ferromagnetic In{sub 1-x}Mn{sub x}As quantum dots (QDs) grown by molecular beam epitaxy (MBE). The ordered In{sub 1-x}Mn{sub x}As QDs were grown on top of a non-magnetic In{sub 0.4}Ga{sub 0.6}As/GaAs(100) QDs multi-layered structure. The modulation of the chemical potential, due to the stacking, provides a nucleation center for the LT In{sub 1-x}Mn{sub x}As QDs. For particular conditions, such as surface morphology and growth conditions, the In{sub 1-x}Mn{sub x}As QDs align along lines like chains. This work also reports the characterization of QDs grown on plain GaAs(100) substrates, as well as of the ordered structures, as function of Mn content and growth temperature. The substitutional Mn incorporation in the InAs lattice and the conditions for obtaining coherent and incoherent structures are discussed from comparison between Raman spectroscopy and x-ray analysis. Ferromagnetic behavior was observed for all structures at 2 K. We found that the magnetic moment axis changes from [110] in In{sub 1-x}Mn{sub x}As over GaAs to [1-10] for the ordered In{sub 1-x}Mn{sub x}As grown over GaAs template.

  12. Mn-doped ZnFe{sub 2}O{sub 4} nanoparticles with enhanced performances as anode materials for lithium ion batteries

    SciTech Connect (OSTI)

    Tang, Xiaoqin; Hou, Xianhua; Yao, Lingmin; Hu, Shejun; Liu, Xiang; Xiang, Liangzhong

    2014-09-15

    Highlights: • Mn-doped ZnFe{sub 2}O{sub 4} nanoparticles have been synthesized by hydrothermal method. • Zn{sub 0.96}Mn{sub 0.04}Fe{sub 2}O{sub 4} electrode shows the highest reversible capacity of 1157 mA h g{sup −1}. • The Zn{sub 0.96}Mn{sub 0.04}Fe{sub 2}O{sub 4} electrode shows promising cycling stability. - Abstract: Nanocrystalline Zn{sub 1−x}Mn{sub x}Fe{sub 2}O{sub 4} (x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) have been successfully synthesized by one-step hydrothermal method. The morphologies and electrochemical performance of Mn-doped ZnFe{sub 2}O{sub 4} in various proportions were investigated at room temperature, respectively. The Zn{sub 1−x}Mn{sub x}Fe{sub 2}O{sub 4} (x = 0.04) electrode in the as-synthesized samples showed the highest specific capacity of 1547 mA h g{sup −1} and 1157 mA h g{sup −1} in the initial discharge/charge process, with a coulombic efficiency of 74.8%. Additionally, excellent cycling stability was performed with a 1214 mA h g{sup −1} capacity retention at a current density of 100 mA g{sup −1} after 50 cycles. The corresponding mechanism was proposed which indicated that the Mn-doped ZnFe{sub 2}O{sub 4} nanoparticles experienced an aggregation thermochemical reaction among ZnO, MnO and Fe{sub 2}O{sub 3} subparticles.

  13. Magnetism in La₂O₃(Fe₁₋xMnx)₂Se₂ tuned by Fe/Mn ratio

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Lei, Hechang; Bozin, Emil S.; Llobet, A.; Ivanovski, V.; Koteski, V.; Belosevic-Cavor, J.; Cekic, B.; Petrovic, C.

    2012-09-17

    We report the evolution of structural and magnetic properties in La₂O₃(Fe₁₋xMnx)₂Se₂. Heat capacity and bulk magnetization indicate an increased ferromagnetic component of the long-range magnetic order and possible increased degree of frustration. Atomic disorder on Fe(Mn) sites suppresses the temperature of the long-range order whereas intermediate alloys show a rich magnetic phase diagram.

  14. Correlating Local Structure with Electrochemical Activity in Li2MnO3

    SciTech Connect (OSTI)

    Nanda, Jagjit; Sacci, Robert L.; Veith, Gabriel M.; Dixit, Hemant M.; Cooper, Valentino R.; Pezeshki, Alan M.; Ruther, Rose E.

    2015-07-31

    Li2MnO3 is of interest as one component of the composite lithium-rich oxides, which are under development for high capacity, high voltage cathodes in lithium ion batteries. Despite such practical importance, the mechanism of electrochemical activity in Li2MnO3 is contested in the literature, as are the effects of long-term electrochemical cycling. Here, Raman spectroscopy and mapping are used to follow the chemical and structural changes that occur in Li2MnO3. Both conventional slurry electrodes and thin films are studied as a function of the state of charge (voltage) and cycle number. Thin films have similar electrochemical properties as electrodes prepared from slurries, but allow for spectroscopic investigations on uniform samples without carbon additives. Spectral changes correlate well with electrochemical activity and support a mechanism whereby capacity is lost upon extended cycling due to the formation of new manganese oxide phases. Raman mapping of both thin film and slurry electrodes charged to different voltages reveals significant variation in the local structure. Poor conductivity and slow kinetics associated with a two-phase reaction mechanism contribute to the heterogeneity.

  15. Kinetics of MN-based sorbents for hot coal gas desulfurization. Semiannual report, December 15, 1996--March 15, 1997

    SciTech Connect (OSTI)

    Hepworth, M.T.

    1997-03-01

    Manganese-based sorbents have been investigated for the removal of hydrogen sulfide (the primary sulfur bearing compound) from hot coal gases prior to its use in combined cycle turbines. Four formulations of Mn-based sorbents were tested in an ambient-pressure fixed-bed reactor to determine steady state H{sub 2}S concentrations, breakthrough times and effectiveness of the sorbent when subjected to cyclic sulfidation and regeneration testing. In previous reports, the sulfidation and regeneration results from cyclic testing done at 600{degrees}C were presented. Manganese-based sorbents with molar ratios >1:1 Mn:substrate were effective in reducing the H{sub 2}S concentration in simulated coal gases to less than 100 ppmv over five cycles. Actual breakthrough time for formulation C6-2-1100 was as high as 73% of breakthrough time based on wt% Mn in sorbent. Regeneration tests determined that loaded pellets can be fully regenerated in air/steam mixture at 750{degrees}C with minimal sulfate formation. In this report, the results from the cyclic crush strength tests, sulfur profile test, and cyclic testing done after 5 cycles showed decreases in strength from 12.6% to 57.9%. Cyclic testing at 550{degrees}C showed pre-breakthrough concentrations as low as 10 ppmv. Cyclic testing done at 2 L/min and 3 L/min did not show any significant difference in pre-breakthrough concentrations or capacity.

  16. Kinetics of Mn-based sorbents for hot coal gas desulfurization. Quarterly report, September 15 - December 15, 1996

    SciTech Connect (OSTI)

    Hepworth, M.T.

    1996-12-31

    Manganese-based sorbents have been investigated for the removal of hydrogen sulfide (the primary sulfur bearing compound) from hot coal gases prior to its use in combined cycle turbines. Four formulations of Mn-based sorbents were tested in an ambient-pressure fixed-bed reactor to determine steady state H{sub 2}S concentrations, breakthrough times and effectiveness of the sorbent when subjected to cyclic sulfidation and regeneration testing. In a previous report, the sulfidation results were presented. Manganese-based sorbents with molar ratios > 1:1 Mn:Substrate were effective in reducing the H{sub 2}S concentration in simulated coal gases to less than 100 ppmv over five cycles. Actual breakthrough time for formulation C6-2-1100 was as high as 73% of breakthrough time based on wt% Mn in sorbent. In this report, the regeneration results will be presented. Regeneration tests determined that loaded pellets can be fully regenerated in air/steam mixture at 750{degrees}C with minimal sulfate formation. 16 refs., 9 figs., 5 tabs.

  17. Determination of elastic properties of a MnO{sub 2} coating by surface acoustic wave velocity dispersion analysis

    SciTech Connect (OSTI)

    Sermeus, J.; Glorieux, C.; Sinha, R.; Vereecken, P. M.; Vanstreels, K.

    2014-07-14

    MnO{sub 2} is a material of interest in the development of high energy-density batteries, specifically as a coating material for internal 3D structures, thus ensuring rapid energy deployment. Its electrochemical properties have been mapped extensively, but there are, to the best of the authors' knowledge, no records of the elastic properties of thin film MnO{sub 2}. Impulsive stimulated thermal scattering (ISTS), also known as the heterodyne diffraction or transient grating technique, was used to determine the Young's modulus (E) and porosity (?) of a 500?nm thick MnO{sub 2} coating on a Si(001) substrate. ISTS is an all optical method that is able to excite and detect surface acoustic waves (SAWs) on opaque samples. From the measured SAW velocity dispersion, the Young's modulus and porosity were determined to be E?=?25??1?GPa and ?=421%, respectively. These values were confirmed by independent techniques and determined by a most-squares analysis of the carefully fitted SAW velocity dispersion. This study demonstrates the ability of the presented technique to determine the elastic parameters of a thin, porous film on an anisotropic substrate.

  18. Nuclear and magnetic supercells in the multiferroic candidate: Pb3TeMn3P2O14

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Silverstein, Harlyn J.; Zhao, Haidong; Wiebe, Christopher; Huq, Ashfia

    2015-01-01

    The dugganites, Te6+-containing members of the langasite series, have attracted recent interest due to their complex low-temperature magnetic unit cells, magnetodielectric, and potentially multiferroic properties. For Pb2+-containing dugganites, a large monoclinic supercell was reported and was found to have a profound effect on the low temperature magnetism and spin excitation spectra. Pb3TeMn3P2O14 is another dugganite previously shown to distort away from the canonical P321 langasite unit cell, although this supercell was never fully solved. Here we report the full crystal and magnetic structure solution of Pb3TeMn3P2O14 using synchrotron x-ray and neutron diffraction data: a large trigonal supercell is observed inmore » this material, which is believed to be the first supercell of its kind in the langasite family. Here, the magnetic structure, high-magnetic field behavior, and dielectric properties of Pb3TeMn3P2O14 are presented. In addition to showing weak magnetoelectric behavior similar to other langasites, it was found that a phase transition occurs at 3 T near the antiferromagnetic transition temperature. (C) 2014 Elsevier Inc. All rights reserved.« less

  19. Magnetoelectric coupling tuned by competing single iron anisotropies in Mn1-xNixTiO3

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Chi, Songxue; Ye, Feng; Zhou, Haidong D.; Choi, E. S.; Hwang, J.; Cao, Huibo; Fernandez-Baca, Jaime A.

    2014-01-01

    A flop of electric polarization from Pc to Pa is observed in MnTiO3 as a spin flop transtion is triggered by a c-axis magnetic field, Hc=7 T. The critical magnetic field for Pa is significantly reduced in Mn1-xNixTiO3 (x=0.33). Neutron diffraction measurements revealed similar magnetic arrangements for the two compositions where the ordered spins couple antiferromagnetically with their nearest intra- and inter-planar neighbors. In the x=0.33 system, the single ion anisotropies of Mn2+ and Ni2+ compete and give rise to an additional spin reorientation transition at TR. A magnetic field, Hc, aligns the spins along c for TRN. The rotationmore » of the collinear spins away from the c-axis for TR alters the magnetic point symmetry and gives rise to new ME susceptibility tensor form. Such linear ME response provides satisfactory explanation for behavior of field-induced electric polarization in both compositions. As the Ni content increases to x=0.5 and 0.68, the ME effect disappears as a new magnetic phase emerges.« less

  20. Observation of the large magnetocaloric effect and suppression of orbital entropy change in Fe-doped MnV{sub 2}O{sub 4}

    SciTech Connect (OSTI)

    Huang, Z. H.; Luo, X. E-mail: ypsun@issp.ac.cn; Hu, L.; Tan, S. G.; Liu, Y.; Yuan, B.; Chen, J.; Song, W. H.; Sun, Y. P. E-mail: ypsun@issp.ac.cn

    2014-01-21

    We present the structural and magnetic properties of Mn{sub 1−x}Fe{sub x}V{sub 2}O{sub 4} (x = 0.1, 0.2, and 0.3), and investigate the magnetocaloric effect in those compounds. The ferrimagnetic spin ordering is enhanced with the Fe doping at Mn site of MnV{sub 2}O{sub 4}, while the orbital ordering is suppressed. Large magnetic entropy changes up to 3.8 J/kg K as well as the relative cooling power up to 110 J/kg at the field change of 0-2 T for Mn{sub 1−x}Fe{sub x}V{sub 2}O{sub 4} are calculated from the isothermal magnetization measurements. The large orbital entropy change of MnV{sub 2}O{sub 4} is suppressed by the Fe doping, while the spin entropy contribution arising from the strong spin-orbit coupling remains. Moreover, the doping of Fe broadens the temperature span of the large magnetic entropy change and increases the relative cooling power of MnV{sub 2}O{sub 4} by 2.4 times.

  1. Nanometer-scale electrochemical patterning of LiMn2O4 surfaces by an atomic force microscope operating in air

    SciTech Connect (OSTI)

    Kostecki, Robert; Bonhomme, Frederic; Servant, Laurent; Argoul, Francoise; McLarnon, Frank

    2001-06-22

    Electrochemical nanometer-scale patterning of the surface of a conducting lithium manganese oxide (LiMn{sub 2}O{sub 4}) by scanning probe microscopy (SPM) was studied. The ability to produce nanometer-size patterns of chemically modified oxide or nanometer-sized alterations of the oxide morphology is demonstrated and discussed with reference to possible mechanisms. It is demonstrated that unlike the SPM-based surface oxidation of metals and semiconductors, the LiMn{sub 2}O{sub 4} surface is altered via electrochemically generated species. We show that a localized surface chemical change can be confined to a depth which depends on the oxide-tip voltage difference and ambient humidity. In situ Raman microscopy measurements of localized electrochemical reaction products suggest complex mechanisms of processes induced at the LiMn{sub 2}O{sub 4} surface, such as delithiation through Li-proton exchange and disproportionation of LiMn{sub 2}O{sub 4} to MnO{sub 2} and soluble Mn{sup 2+} species.

  2. X-ray magnetic spectroscopy of MBE-grown Mn-doped Bi{sub 2}Se{sub 3} thin films

    SciTech Connect (OSTI)

    Collins-McIntyre, L. J.; Watson, M. D.; Zhang, S. L.; Coldea, A. I.; Hesjedal, T.; Baker, A. A.; Harrison, S. E.; Pushp, A.; Kellock, A. J.; Parkin, S. S. P.; Laan, G. van der

    2014-12-15

    We report the growth of Mn-doped Bi{sub 2}Se{sub 3} thin films by molecular beam epitaxy (MBE), investigated by x-ray diffraction (XRD), atomic force microscopy (AFM), SQUID magnetometry and x-ray magnetic circular dichroism (XMCD). Epitaxial films were deposited on c-plane sapphire substrates by co-evaporation. The films exhibit a spiral growth mechanism typical of this material class, as revealed by AFM. The XRD measurements demonstrate a good crystalline structure which is retained upon doping up to ?7.5 atomic-% Mn, determined by Rutherford backscattering spectrometry (RBS), and show no evidence of the formation of parasitic phases. However an increasing interstitial incorporation of Mn is observed with increasing doping concentration. A magnetic moment of 5.1 ?{sub B}/Mn is obtained from bulk-sensitive SQUID measurements, and a much lower moment of 1.6 ?{sub B}/Mn from surface-sensitive XMCD. At ?2.5 K, XMCD at the Mn L{sub 2,3} edge, reveals short-range magnetic order in the films and indicates ferromagnetic order below 1.5 K.

  3. Crystallographic, magnetic, and electronic structures of ferromagnetic shape memory alloys Ni{sub 2}XGa (X=Mn,Fe,Co) from first-principles calculations

    SciTech Connect (OSTI)

    Bai, J.; Raulot, J. M.; Zhang, Y. D.; Esling, C.; Zhao, X.; Zuo, L.

    2011-01-01

    The crystallographic, magnetic and electronic structures of the ferromagnetic shape memory alloys Ni{sub 2}XGa (X=Mn, Fe, and Co), are systematically investigated by means of the first-principles calculations within the framework of density functional theory using the VIENNA AB INITIO SOFTWARE PACKAGE. The lattice parameters of both austenitic and martensitic phases in Ni{sub 2}MnGa have been calculated. The formation energies of the cubic phase of Ni{sub 2}XGa are estimated, and show a destabilization tendency if Mn atom is substituted by Fe or Co. From Ni{sub 2}MnGa to Ni{sub 2}CoGa, the down spin total density of states (DOS) at Fermi level is gradually increasing, whereas that of the up spin part remains almost unchanged. This is the main origin of the difference of the magnetic moment in these alloys. The partial DOS is dominated by the Ni and Mn 3d states in the bonding region below E{sub F}. There are two bond types existing in Ni{sub 2}XGa: one is between neighboring Ni atoms in Ni{sub 2}MnGa; the other is between Ni and X atoms in Ni{sub 2}FeGa and Ni{sub 2}CoGa alloys.

  4. Low temperature growth of Co{sub 2}MnSi films on diamond semiconductors by ion-beam assisted sputtering

    SciTech Connect (OSTI)

    Nishiwaki, M.; Ueda, K. Asano, H.

    2015-05-07

    High quality Schottky junctions using Co{sub 2}MnSi/diamond heterostructures were fabricated. Low temperature growth at ∼300–400 °C by using ion-beam assisted sputtering (IBAS) was necessary to obtain abrupt Co{sub 2}MnSi/diamond interfaces. Only the Co{sub 2}MnSi films formed at ∼300–400 °C showed both saturation magnetization comparable to the bulk values and large negative anisotropic magnetoresistance, which suggests half-metallic nature of the Co{sub 2}MnSi films, of ∼0.3% at 10 K. Schottky junctions formed using the Co{sub 2}MnSi films showed clear rectification properties with rectification ratio of more than 10{sup 7} with Schottky barrier heights of ∼0.8 eV and ideality factors (n) of ∼1.2. These results indicate that Co{sub 2}MnSi films formed at ∼300–400 °C by IBAS are a promising spin source for spin injection into diamond semiconductors.

  5. Electrode Materials with the Na0.44MnO2 Structure: Effect ofTitanium Substitution on Physical and Electrochemical Properties

    SciTech Connect (OSTI)

    Doeff, Marca M; Saint, Juliette A.; Doeff, Marca M; Wilcox, James D.

    2008-03-10

    The physical and electrochemical properties of LixMnO2 and LixTi0.11Mn0.89O2 synthesized from precursors made by glycine-nitrate combustion (GNC) and solid-state synthesis methods (SS) are examined in this paper. The highest specific capacities in lithium cells are obtained for SS-LixMnO2 electrodes at low current densities, but GNC-LixTi0.11Mn0.89O2 electrodes show the best high rate performance. These results can be explained by changes in the voltage characteristics and differences in the particle morphologies induced by the Ti-substitution and synthesis method. Ti-substitution also results in a decrease in the electronic conductivity, but greatly improves the thermal properties and imparts dissolution resistance to the electrode. For these reasons, it is preferable to use LixTi0.11MnO0.89O2 in lithium battery configurations rather than LixMnO2. Suggestions for improving the electrochemical performance of the Ti-substituted variant are given based on the results described herein.

  6. Structural investigations on Co{sub 3-x}Mn{sub x}TeO{sub 6}; (0 < x ? 2); High temperature ferromagnetism and enhanced low temperature anti-ferromagnetism

    SciTech Connect (OSTI)

    Singh, Harishchandra; Sinha, A. K. E-mail: hng@rrcat.gov.in; Ghosh, Haranath E-mail: hng@rrcat.gov.in; Singh, M. N.; Rajput, Parasmani; Prajapat, C. L.; Singh, M. R.; Ravikumar, G.

    2014-08-21

    In the quest of materials with high temperature ferromagnetism and low temperature anti-ferromagnetism, we prepare Co{sub 3-x}Mn{sub x}TeO{sub 6}; (0?Mn concentration using Synchrotron X-ray diffraction (SXRD) and X-ray absorption near edge structure measurements in corroboration with magnetism are presented. Phase diagram obtained from Rietveld Refinement on SXRD data as a function of Mn concentration indicates doping disproportionate mixing of both monoclinic (C2/c) and rhombohedral (R 3{sup }) structure for x?Mn-O) bond lengths for x???0.5. Co and Mn K-edge XANES spectra reveal that both Co and Mn are in mixed oxidation state, Co{sup 2+}/Mn{sup 2+} and Co{sup 3+}/Mn{sup 3+}. Relative ratios of Co{sup 3+}/Co{sup 2+} and Mn{sup 3+}/Mn{sup 2+} obtained using Linear combination fit decrease with increasing x (for x???0.5). These structural and spectroscopic evidences are used to provide possible interpretation of the observed paramagnetic to ferromagnetic transition at around 185?K followed by an enhanced antiferromagnetic transition ?45?K for x?=?0.5.

  7. Magnetic Response of Mn(III)F(salen) at Low Temperatures

    SciTech Connect (OSTI)

    Park, J. - H.; Risset, O. N.; Shiddiq, M.; Peprah, M. K.; Knowles, E. S.; Andrus, Matthew; Beedle, C. C.; Ehlers, Georg; Podlesnyak, Andrey A; Cizmar, E.; Nagler, Stephen E; Hill, S.; Talham, Daniel R.; Meisel, Mark W.

    2014-01-01

    The low temperature magnetic response of Mn(III)F(salen), salen = H14C16N2O2, an S = 2 linear-chain system, has been studied. Using a single crystal with the field applied perpendicular to the chain direction, torque magnetometry, down to 20 mK and up to 18 T, revealed a feature at 3.8 T when T 400 mK. ESR ( 200 GHz) studies, using single crystals at 4 K and in 5 T, have not detected any signal. In 10 mT, the temperature dependence of the susceptibility of powder-like samples can be reasonably fit when J/kB = 50 K and g = 2. In addition, these data are unchanged for P 1.0 GPa. Using a randomly-oriented, powder-like, deuterated (12 of 14 H replaced by D) sample of 2.2 g at 270 mK, neutron scattering data, acquired with the Cold Neutron Chopper Spectrometer at the Spallation Neutron Source, show several well defined excitations that may be from the zero-field energy levels of antiferromagnetic S = 2 spins with g = 2, J/kB = 50 K, D/kB = 2.8 K, and E/kB = 0.5 K.

  8. Stress induced anisotropy in CoFeMn soft magnetic nanocomposites

    SciTech Connect (OSTI)

    Leary, A. M. Keylin, V.; McHenry, M. E.; Ohodnicki, P. R.

    2015-05-07

    The use of processing techniques to create magnetic anisotropy in soft magnetic materials is a well-known method to control permeability and losses. In nanocomposite materials, field annealing below the Curie temperature results in uniaxial anisotropy energies up to ?2?kJ/m{sup 3}. Higher anisotropies up to ?10?kJ/m{sup 3} result after annealing Fe-Si compositions under stress due to residual stress in the amorphous matrix acting on body centered cubic crystals. This work describes near zero magnetostriction Co{sub 80?x?y}Fe{sub x}Mn{sub y}Nb{sub 4}B{sub 14}Si{sub 2} soft magnetic nanocomposites, where x and y?

  9. Pressure dependence of the magnetic ground states in MnP

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Matsuda, Masaaki; Ye, Feng; Dissanayake, Sachith E.; Cheng, J. -G.; Chi, Songxue; Ma, Jie; Zhou, H. D.; Yan, Jia -Qiang; Kasamatsu, S.; Sugino, O.; et al

    2016-03-17

    MnP, a superconductor under pressure, exhibits a ferromagnetic order below TC~290 K followed by a helical order with the spins lying in the ab plane and the helical rotation propagating along the c axis below Ts~50 K at ambient pressure. We performed single-crystal neutron diffraction experiments to determine the magnetic ground states under pressure. Both TC and Ts are gradually suppressed with increasing pressure and the helical order disappears at ~1.2 GPa. At intermediate pressures of 1.8 and 2.0 GPa, the ferromagnetic order first develops and changes to a conical or two-phase (ferromagnetic and helical) structure with the propagation alongmore » the b axis below a characteristic temperature. At 3.8 GPa, a helical magnetic order appears below 208 K, which hosts the spins in the ac plane and the propagation along the b axis. The period of this b axis modulation is shorter than that at 1.8 GPa. Here, our results indicate that the magnetic phase in the vicinity of the superconducting phase may have a helical magnetic correlation along the b axis.« less

  10. Pressure-Induced Enhanced Magnetic Anisotropy in Mn(N(CN)2)2

    SciTech Connect (OSTI)

    Quintero, P. A.; Rajan, D.; Peprah, M. K.; Brinzari, T. V.; Fishman, Randy Scott; Talham, Daniel R.; Meisel, Mark W.

    2015-01-01

    Using DC and AC magnetometry, the pressure dependence of the magnetization of the threedimensional antiferromagnetic coordination polymer Mn(N(CN)2)2 was studied up to 12 kbar and down to 8 K. The magnetic transition temperature, Tc, increases dramatically with applied pressure (P), where a change from Tc(P = ambient) = 16:0 K to Tc(P = 12:1 kbar) = 23:5 K was observed. In addition, a marked difference in the magnetic behavior is observed above and below 7.1 kbar. Specifically, for P < 7:1 kbar, the differences between the field-cooled and zero-field-cooled (fc-zfc) magnetizations, the coercive field, and the remanent magnetization decrease with increasing pressure. However, for P > 7:1 kbar, the behavior is inverted. Additionally, for P > 8:6 kbar, minor hysteresis loops are observed. All of these effects are evidence of the increase of the superexchange interaction and the appearance of an enhanced exchange anisotropy with applied pressure.

  11. Structural, magnetic, and transport properties of sputtered hexagonal MnNiGa thin films

    SciTech Connect (OSTI)

    Li, Yueqing; Liu, E. K.; Wu, G. H.; Wang, Wenhong; Liu, Zhongyuan

    2014-12-14

    We report on a systematical study of the structure, magnetism, and magnetotransport behavior of the hexagonal MnNiGa films deposited on thermally oxidized Si (001) substrates by magnetron sputtering. X-ray diffractions reveal that all the films deposited at different temperatures crystallized in hexagonal Ni{sub 2}In-type structure (space group P6{sub 3}/mmc). Scanning electron microscopy observations show that the surface morphology of the films varies with deposition temperature, and energy dispersive spectroscopy analysis shows compositions of the films remain nearly unchanged, independent of the deposition temperature. Magnetic measurements indicate that all films are ferromagnetic and exhibit a magnetic anisotropy behavior. The magnetoresistance (MR) exhibits a negative temperature- and field-dependent behavior. The possible origin of the negative MR is discussed. Furthermore, we found that the Hall effect is dominated by an anomalous Hall effect (AHE) only due to skew scattering independent of the deposition temperature of films. Moreover, the anomalous Hall resistivity presents a non-monotonously temperature-dependent behavior.

  12. Thermal-history dependent magnetoelastic transition in (Mn,Fe){sub 2}(P,Si)

    SciTech Connect (OSTI)

    Miao, X. F. Dijk, N. H. van; Brück, E.; Caron, L.; Gercsi, Z.; Daoud-Aladine, A.

    2015-07-27

    The thermal-history dependence of the magnetoelastic transition in (Mn,Fe){sub 2}(P,Si) compounds has been investigated using high-resolution neutron diffraction. As-prepared samples display a large difference in paramagnetic-ferromagnetic (PM-FM) transition temperature compared to cycled samples. The initial metastable state transforms into a lower-energy stable state when the as-prepared sample crosses the PM-FM transition for the first time. This additional transformation is irreversible around the transition temperature and increases the energy barrier which needs to be overcome through the PM-FM transition. Consequently, the transition temperature on first cooling is found to be lower than on subsequent cycles characterizing the so-called “virgin effect.” High-temperature annealing can restore the cycled sample to the high-temperature metastable state, which leads to the recovery of the virgin effect. A model is proposed to interpret the formation and recovery of the virgin effect.

  13. Orbital two-channel Kondo effect in epitaxial ferromagnetic L10-MnAl films

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zhu, L. J.; Nie, S. H.; Xiong, P.; Schlottmann, P.; Zhao, J. H.

    2016-02-24

    The orbital two-channel Kondo effect displaying exotic non-Fermi liquid behaviour arises in the intricate scenario of two conduction electrons compensating a pseudo-spin-1/2 impurity of two-level system. Despite extensive efforts for several decades, no material system has been clearly identified to exhibit all three transport regimes characteristic of the two-channel Kondo effect in the same sample, leaving the interpretation of the experimental results a subject of debate. Here we present a transport study suggestive of a robust orbital two-channel Kondo effect in epitaxial ferromagnetic L10-MnAl films, as evidenced by a magnetic field-independent resistivity upturn with a clear transition from logarithmic- tomore » square-root temperature dependence and deviation from it in three distinct temperature regimes. Lastly, our results also provide an experimental indication of the presence of two-channel Kondo physics in a ferromagnet, pointing to considerable robustness of the orbital two-channel Kondo effect even in the presence of spin polarization of the conduction electrons.« less

  14. Polar-graded multiferroic SrMnO3 thin films

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Lupini, Andrew R.; Guzman, Roger; Maurel, Laura; Langenberg, Eric; Algarabel, Pedro A.; Pardo, Jose A.; Magen, Cesar

    2016-03-21

    Engineering defects and strains in oxides provides a promising route for the quest of thin film materials with coexisting ferroic orders, multiferroics, with efficient magnetoelectric coupling at room temperature. Precise control of the strain gradient would enable custom tailoring of the multiferroic properties but presently remains challenging. Here we explore the existence of a polar-graded state in epitaxially strained antiferromagnetic SrMnO3 thin films, whose polar nature was predicted theoretically and recently demonstrated experimentally. By means of aberration-corrected scanning transmission electron microscopy we map the polar rotation of the ferroelectric polarization with atomic resolution, both far from and near the domainmore » walls, and find flexoelectricity resulting from vertical strain gradients. The origin of this particular strain state is a gradual distribution of oxygen vacancies across the film thickness, according to electron energy loss spectroscopy. Furthermore, we present a chemistry-mediated route to induce polar rotations in oxygen-deficient multiferroic films, resulting in flexoelectric polar rotations and with potentially enhanced piezoelectricity.« less

  15. Phase diagram and magnetocaloric effects in Ni{sub 50}Mn{sub 35}(In{sub 1?x}Cr{sub x}){sub 15} and (Mn{sub 1?x}Cr{sub x})NiGe{sub 1.05} alloys

    SciTech Connect (OSTI)

    Quetz, Abdiel Muchharla, Baleeswaraiah; Dubenko, Igor; Talapatra, Saikat; Ali, Naushad; Samanta, Tapas; Stadler, Shane

    2014-05-07

    The magnetocaloric and thermomagnetic properties of Ni{sub 50}Mn{sub 35}(In{sub 1?x}Cr{sub x}){sub 15} and (Mn{sub 1?x}Cr{sub x}) NiGe{sub 1.05} systems for 0???x???0.105 and 0???x???0.1, respectively, have been studied by x-ray diffraction, differential scanning calorimetry, and magnetization measurements. Partial substitution of Cr for Mn in (Mn{sub 1?x}Cr{sub x})NiGe{sub 1.05} results in a first order magnetostructural transition from a hexagonal paramagnetic to an orthorhombic paramagnetic phase near T{sub M}???380?K (for x?=?0.07). Partial substitution of Cr for In in Ni{sub 50}Mn{sub 35}(In{sub 1?x}Cr{sub x}){sub 15} shifts the magnetostructural transition to a higher temperature (T?=?T{sub M}???450?K) for x?=?0.1. Large magnetic entropy changes of ?S?=??12 (J/(kgK)) and ?S?=??11 (J/(kgK)), both for a magnetic field change of 5?T, were observed in the vicinity of T{sub M} for (Mn{sub 1?x}Cr{sub x})NiGe{sub 1.05} and Ni{sub 50}Mn{sub 35}(In{sub 1?x}Cr{sub x}){sub 15}, respectively.

  16. Manipulating the ferromagnetism in narrow-bandwidth Pr{sub 1-x}Ca{sub x}MnO{sub 3} (0 ≤ x ≤ 0.6) by means of the Mn-Ru t{sub 2g} ferromagnetic super-exchanges

    SciTech Connect (OSTI)

    Wang, Y. L.; Liu, M. F.; Xie, Y. L.; Yan, Z. B.; Dong, S.; Liu, J.-M.

    2015-09-28

    The concurrent ferromagnetic and metal-insulator transitions via the double-exchange route and electronic phase separation scenario represent the core ingredients of the physics of manganites. In this work, a Ca{sup 2+} and Ru{sup 4+} co-substitution of Pr{sup 3+} and Mn{sup 3+} in narrow-bandwidth and insulating PrMnO{sub 3}, namely, Pr{sub 1-x}Ca{sub x}Mn{sub 1-x}Ru{sub x}O{sub 3} (PCMRO, x ≤ 0.6), is carried out in order to investigate an alternative approach to effectively manipulate the ferromagnetism of PrMnO{sub 3}-based manganites. It is revealed that PCMRO over the whole substitution range is homogeneous solid solution with increased lattice distortion. The preference of Ru{sup 4+} valence state and the absence of Mn{sup 4+} valence state disable the Mn{sup 3+}-Mn{sup 4+} e{sub g}-orbital double-exchange, and the random occupation of Ru{sup 4+} in the lattice excludes the charge ordering and electronic phase separation. While all these consequences should favor antiferromagnetic insulating states, nevertheless, a high-temperature ferromagnetic transition is triggered by the co-substitution and the magnetization can reach up to ∼1.0 μ{sub B}/f.u. at x ∼ 0.2–0.3, much bigger than the moment (<0.1 μ{sub B}/f.u.) of Pr{sub 1−x}Ca{sub x}MnO{sub 3} in the weak ferromagnetic insulator state. It is suggested that this strong ferromagnetism is substantially ascribed to the Mn{sup 3+}-Ru{sup 4+} t{sub 2g}-orbital ferromagnetic super-exchange, and a simple geometric network illustration of the magnetism and electrical transport is presented.

  17. Redox Exchange Induced MnO2 Nanoparticle Enrichment in Poly(3,4-ethylenedioxythiophene) Nanowires for Electrochemical Energy Storage

    SciTech Connect (OSTI)

    Liu, R.; Duay, Jonathon; Lee, Sang Bok

    2010-06-30

    MnO2 nanoparticle enriched poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires are fabricated by simply soaking the PEDOT nanowires in potassium permanganate (KMnO4) solution. The structures of these MnO2 nanoparticle enriched PEDOT nanowires are characterized by SEM and TEM, which show that the MnO2 nanoparticles have uniform sizes and are finely dispersed in the PEDOT matrix. The chemical constituents and bonding of these composite nanowires are characterized by energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, and infrared spectroscopy, which indicate that the formation and dispersion of these MnO2 nanoparticles into the nanoscale pores of the PEDOT nanowires are most likely triggered by the reduction of KMnO4 via the redox exchange of permanganate ions with the functional group on PEDOT. Varying the concentrations of KMnO4 and the reaction time controls the loading amount and size of the MnO2 nanoparticles. Cyclic voltammetry and galvanostatic charge-discharge are used to characterize the electrochemical properties of these MnO2 nanoparticle loaded PEDOT nanowires. Due to their extremely high exposed surface area with nanosizes, the pristine MnO2 nanoparticles in these MnO2 nanoparticle enriched PEDOT nanowires show very high specific capacitance (410 F/g) as the supercapacitor electrode materials as well as high Li+ storage capacity (300 mAh/g) as cathode materials of Li ion battery, which boost the energy storage capacity of PEDOT nanowires to 4 times without causing excessive volume expansion in the polymer. The highly conductive and porous PEDOT matrix facilitates fast charge/discharge of the MnO2 nanoparticles and prevents them from agglomerating. These synergic properties enable the MnO2 nanoparticle enriched PEDOT nanowires to be promising electrode materials for supercapacitors and

  18. Insight into the Atomic Structure of High-Voltage Spinel LiNi0.5Mn1.5O4 Cathode Material in the First Cycle

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Huang, Xuejie; Yu, Xiqian; Lin, Mingxiang; Ben, Liubin; Sun, Yang; Wang, Hao; Yang, Zhenzhong; Gu, Lin; Yang, Xiao -Qing; Zhao, Haofei; et al

    2014-12-22

    Application of high-voltage spinel LiNi0.5Mn1.5O4 cathode material is the closest and the most realistic approach to meeting the midterm goal of lithium-ion batteries for electric vehicles (EVs) and plug-in hybrid electric vehicles (HEVs). However, this application has been hampered by long-standing issues, such as capacity degradation and poor first-cycle Coulombic efficiency of LiNi0.5Mn1.5O4 cathode material. Although it is well-known that the structure of LiNi0.5Mn1.5O4 into which Li ions are reversibly intercalated plays a critical role in the above issues, performance degradation related to structural changes, particularly in the first cycle, are not fully understood. Here, we report detailed investigations ofmore » local atomic-level and average structure of LiNi0.5Mn1.5O4 during first cycle (3.5–4.9 V) at room temperature. We observed two types of local atomic-level migration of transition metals (TM) ions in the cathode of a well-prepared LiNi0.5Mn1.5O4//Li half-cell during first charge via an aberration-corrected scanning transmission electron microscopy (STEM). Surface regions (~2 nm) of the cycled LiNi0.5Mn1.5O4 particles show migration of TM ions into tetrahedral Li sites to form a Mn3O4-like structure. However, subsurface regions of the cycled particles exhibit migration of TM ions into empty octahedral sites to form a rocksalt-like structure. The migration of these TM ions are closely related to dissolution of Ni/Mn ions and building-up of charge transfer impedance, which contribute significantly to the capacity degradation and the poor first-cycle Coulombic efficiency of spinel LiNi0.5Mn1.5O4 cathode material. Accordingly, we provide suggestions of effective stabilization of LiNi0.5Mn1.5O4 structure to obtain better electrochemical performance.« less

  19. Combined effects of Bi deficiency and Mn substitution on the structural transformation and functionality of BiFeO{sub 3} films

    SciTech Connect (OSTI)

    Chen, Jingyi; Wang, Yao Deng, Yuan

    2014-11-07

    Mn-doped BiFeO{sub 3} films with Mn contents of 5 and 10 mol. % were prepared via a chemical route. A carefully controlled amount of Bi deficiency was introduced to further tune the lattice structure and the functionality of multiferroic BiFeO{sub 3}. The crystal structure of Bi{sub 1−δ}Fe{sub 1−x}Mn{sub x}O{sub 3} films was investigated by X-ray diffraction and Raman spectra; a rhombohedral-to-orthorhombic phase transition was revealed. The observed double hysteresis loops and two capacitance maxima from polarization vs electric field and capacitance-voltage measurements indicate an antiferroelectric-like behavior. Additionally, the coexistence of ferroelectric (FE) and antiferroelectric (AFE) phases in Bi{sub 1−δ}Fe{sub 1−x}Mn{sub x}O{sub 3} films was revealed from the domain structures obtained by piezoelectric force microscopy. The effects of Mn substitution in conjunction with Bi deficiency on the FE-AFE phase transition and electrical behavior of BiFeO{sub 3} films are discussed in detail. Meanwhile, magnetic and photoluminescence measurements on the films illustrate that Mn substitution gives rise to the net magnetic moment and the defects induced by both Bi deficiency and Mn substitution influence the electronic structure of BiFeO{sub 3} films. This study thus shows a simple and effective way to control the functionalities of BiFeO{sub 3} films.

  20. Structural and Electrochemical Investigation of Li(Ni0.4Co0.2-yAlyMn0.4)O2 Cathode Material

    SciTech Connect (OSTI)

    Rumble, C.; Conry, T.E.; Doeff, Marca; Cairns, Elton J.; Penner-Hahn, James. E.; Deb, Aniruddha

    2010-02-02

    Li(Ni{sub 0.4}Co{sub 0.2-y}Al{sub y}Mn{sub 0.4})O{sub 2} with y=0.05 was investigated to understand the effect of replacement of the cobalt by aluminum on the structural and electrochemical properties. The effect of the substitution was studied by in-situ X-ray absorption spectroscopy (XAS), utilizing a novel in situ electrochemical cell, specifically designed for long-term X-ray experiments. The cell was cycled at a moderate rate through a typical Li-ion battery operating voltage range (1.0-4.7 V). XAS measurements were performed at different states-of-charge (SOC) during cycling, at the Ni, Co, and the Mn edges, revealing details about the response of the cathode to Li insertion and extraction processes. The extended X-ray absorption fine structure region of the spectra revealed the changes of bond distance and coordination number of Ni, Co, and Mn absorbers as a function of the SOC of the material. The oxidation states of the transition metals in the system are Ni{sup 2+}, Co{sup 3+}, and Mn{sup 4+} in the as-made material (fully discharged), while during charging the Ni{sup 2+} is oxidized to Ni{sup 4+} through an intermediate stage of Ni{sup 3+}, Co{sup 3+} is oxidized towards Co{sup 4+} and Mn was found to be electrochemically inactive and remains as Mn{sup 4+}. The EXAFS results during cycling show that the Ni-O changes the most, followed by Co-O and Mn-O varies the least. These measurements on this cathode material confirmed that the material retains its symmetry and good structural short-range order leading to the superior cycling reported earlier.

  1. Effect of Mn doping on structural and magnetic susceptibility of C-type rare earth nano oxides Er{sub 2?x}Mn{sub x}O{sub 3}

    SciTech Connect (OSTI)

    Heiba, Zein K.; Taif University, Faculty of Science, Physics Department ; Mohamed, Mohamed Bakr; Fuess, H.

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ? Er{sub 2?x}Mn{sub x}O{sub 3} (0.0 ? x ? 0.20) prepared by solgel method. ? The change in lattice parameter is not linear with x due to the change in crystallite size with doping. ? Anomalous concentration dependence is found in magnetic susceptibility. ? The effective magnetic moment ?{sub eff} is found to decrease with composition parameter x. ? Superexchange interactions between Er ions depending on the amount of Mn or Er in different sites. -- Abstract: The manganese doped rare earth oxides Er{sub 2?x}Mn{sub x} O{sub 3} (0.0 ? x ? 0.20) were synthesized by a solgel process and analyzed by X-ray diffraction using Rietveld refinement methods. A single phase solid solution is formed up to x = 0.15 while for x ? 0.2 a manganese oxide phase appears in the diffraction pattern. Preferential cationic distribution between the non-equivalent sites 8b and 24d of space group Ia3{sup } is found for all samples but to a different extent. The octahedral volume and average bond length of Er{sub 1}-O for 8b site decrease while both octahedral volume and bond length of Er{sub 2}-O for 24d site increase. Magnetization measurements were done in the temperature range 5300 K. The effective magnetic moment ?{sub eff} is found to decrease with composition parameter x, except for sample x = 0.05 where the magnetization is enhanced. The Curie-Weiss paramagnetic temperatures indicate antiferromagnetic interaction.

  2. Crystal chemical modeling of the Li ion distribution in Li{sub x}Mn{sub 2}O{sub 4}

    SciTech Connect (OSTI)

    Rohrer, C.L.; Rohrer, G.S.

    1996-12-31

    The Monte Carlo bond valence method was used to model the local atomic structure of Li{sub x}Mn{sub 2}O{sub 4} (x = 0.25 and x = 1.0). The results predict that Mn{sup +3} and Mn{sup +4} are randomly distributed at the octahedral positions and that the Mn{sup +3}-O bond distance is 2.02 {Angstrom} while the Mn{sup +4}-O distance is 1.91 {Angstrom}. As the Li content decreases, the cell contracts due to the higher concentration of shorter bonds. Based on maps that show the distribution of crystal chemically equivalent sites, we conclude that the Li ion diffusion paths go through 48f sites, that Li might be more mobile for the case of x = 1.0 than for x = 0.25 (due to the expanded cell volume), and that for x > 1, the 16c position is the most likely Li site.

  3. Magnetic and structural properties of ferromagnetic Fe5PB2 and Fe5SiB2 and effects of Co and Mn substitutions

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    McGuire, Michael A.; Parker, David S.

    2015-10-22

    Crystallographic and magnetic properties of Fe5PB2, Fe4CoPB2, Fe4MnPB2, Fe5SiB2, Fe4CoSiB2, and Fe4MnSiB2 are reported. All adopt the tetragonal Cr5B3 structure-type and are ferromagnetic at room temperature with easy axis of magnetization along the c-axis. The spin reorientation in Fe5SiB2 is observed as an anomaly in the magnetization near 170 K, and is suppressed by substitution of Co or Mn for Fe. The silicides are found to generally have larger magnetic moments than the phosphides, but the data suggests smaller magnetic anisotropy in the silicides. Cobalt substitution reduces the Curie temperatures by more than 100 K and ordered magnetic moments bymore » 16-20%, while manganese substitution has a much smaller effect. This suggests Mn moments align ferromagnetically with the Fe and that Co does not have an ordered moment in these structures. Anisotropic thermal expansion is observed in Fe5PB2 and Fe5SiB2, with negative thermal expansion seen along the c-axis of Fe5SiB2. First principles calculations of the magnetic properties of Fe5SiB2 and Fe4MnSiB2 are reported. The results, including the magnetic moment and anisotropy, and are in good agreement with experiment.« less

  4. Influence of Mn concentration on magnetic topological insulator MnxBi2−xTe3 thin-film Hall-effect sensor

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Ni, Y.; Zhang, Z.; Nlebedim, I. C.; Hadimani, R. L.; Jiles, D. C.

    2015-06-11

    Hall-effect (HE) sensors based on high-quality Mn-doped Bi2Te3 topological insulator (TI) thin films have been systematically studied in this paper. Improvement of Hall sensitivity is found after doping the magnetic element Mn into Bi2Te3. The sensors with low Mn concentrations, MnxBi2-xTe3, x = 0.01 and 0.08 show the linear behavior of Hall resistance with sensitivity about 5 Ω/T. And their Hall sensitivity shows weak dependence on temperature. For sensors with high Mn concentration (x = 0.23), the Hall resistance with respect to magnetic field shows a hysteretic behavior. Moreover, its sensitivity shows almost eight times as high as that ofmore » the HE sensors with low Mn concentration. The highest sensitivity can reach 43 Ω/T at very low magnetic field. This increase of Hall sensitivity is caused by the occurrence of anomalous HE (AHE) after ferromagnetic phase transition. Our work indicates that the magnetic-element-doped TIs with AHE are good candidates for HE sensors.« less

  5. Electronic structures and magnetic stabilities of 2D Mn-doped GaAs nanosheets: The role of long-range exchange interactions and doping strategies

    SciTech Connect (OSTI)

    Lan, Mu; Xiang, Gang Zhang, Xi

    2014-08-28

    We investigate the structural, electronic and magnetic properties of Mn atoms doped two-dimensional (2D) hexagonal GaAs nanosheets (GaAsNSs) using both first-principle calculations and Monte Carlo simulations. The first-principle molecular dynamics is first used to test the structural stability of Mn-doped GaAsNS ((Ga,Mn)AsNS). The analysis of spin-resolved electronic structures and determination of magnetic exchange interactions based on density functional theory (DFT) calculations reveals the existence of long-range exchange interaction in the system. Finally, Metropolis Monte Carlo simulation is employed to estimate Curie temperatures (T{sub C}s) of (Ga,Mn)AsNSs with different doping concentrations by different doping strategies. The results indicate that a T{sub C} up to 82 K can be obtained in regularly-doped (Ga,Mn)AsNSs and doping strategies have prominent impact on T{sub C}s of the systems, which emphasizes the importance of both long-range interactions and doping strategies in reduced dimensional diluted magnetic semiconductors (DMSs)

  6. Influence of Mn concentration on magnetic topological insulator MnxBi2−xTe3 thin-film Hall-effect sensor

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Ni, Y.; Zhang, Z.; Nlebedim, I. C.; Hadimani, R. L.; Jiles, D. C.

    2015-06-11

    Hall-effect (HE) sensors based on high-quality Mn-doped Bi2Te3 topological insulator (TI) thin films have been systematically studied in this paper. Improvement of Hall sensitivity is found after doping the magnetic element Mn into Bi2Te3. The sensors with low Mn concentrations, MnxBi2-xTe3, x = 0.01 and 0.08 show the linear behavior of Hall resistance with sensitivity about 5 Ω/T. And their Hall sensitivity shows weak dependence on temperature. For sensors with high Mn concentration (x = 0.23), the Hall resistance with respect to magnetic field shows a hysteretic behavior. Moreover, its sensitivity shows almost eight times as high as that ofmore »the HE sensors with low Mn concentration. The highest sensitivity can reach 43 Ω/T at very low magnetic field. This increase of Hall sensitivity is caused by the occurrence of anomalous HE (AHE) after ferromagnetic phase transition. Our work indicates that the magnetic-element-doped TIs with AHE are good candidates for HE sensors.« less

  7. Structural phase transition and magnetism in hexagonal SrMnO{sub 3} by magnetization measurements and by electron, x-ray, and neutron diffraction studies

    SciTech Connect (OSTI)

    Daoud-Aladine, A.; Chapon, L. C.; Knight, K. S.; Martin, C.; Hervieu, M.; Brunelli, M.; Radaelli, P. G.

    2007-03-01

    The structural and magnetic properties of the hexagonal four-layer form of SrMnO{sub 3} have been investigated by combining magnetization measurements, electron diffraction, and high-resolution synchrotron x-ray and neutron powder diffraction. Below 350 K, there is subtle structural phase transition from hexagonal symmetry (space group P6{sub 3}/mmc) to orthorhombic symmetry (space group C222{sub 1}) where the hexagonal metric is preserved. The second-order phase transition involves a slight tilting of the corner-sharing Mn{sub 2}O{sub 9} units composed of two face-sharing MnO{sub 6} octahedra and the associated displacement of Sr{sup 2+} cations. The phase transition is described in terms of symmetry-adapted displacement modes of the high symmetry phase. Upon further cooling, long range magnetic order with propagation vector k=(0,0,0) sets in below 300 K. The antiferromagnetic structure, analyzed using representation theory, shows a considerably reduced magnetic moment indicating the crucial role played by direct exchange between Mn centers of the Mn{sub 2}O{sub 9} units.

  8. Preparation of magnetic photocatalyst nanoparticlesTiO{sub 2}/SiO{sub 2}/MnZn ferriteand its photocatalytic activity influenced by silica interlayer

    SciTech Connect (OSTI)

    Laohhasurayotin, Kritapas; Pookboonmee, Sudarat; Viboonratanasri, Duangkamon; Kangwansupamonkon, Wiyong

    2012-06-15

    Highlights: ? TiO{sub 2}/SiO{sub 2}/MnZn ferrite acts as magnetic photocatalyst nanoparticle. ? SiO{sub 2} interlayer is used to prevent electron migration between photocatalyst and magnetic core. ? TiO{sub 2}/MnZn ferrite without SiO{sub 2} interlayer shows poor magnetic and photocatalytic property. -- Abstract: A magnetic photocatalyst, TiO{sub 2}/SiO{sub 2}/MnZn ferrite, was prepared by stepwise synthesis involving the co-precipitation of MnZn ferrite as a magnetic core, followed by a coating of silica as the interlayer, and titania as the top layer. The particle size and distribution of magnetic nanoparticles were found to depend on the addition rate of reagent and dispersing rate of reaction. The X-ray diffractometer and transmission electron microscope were used to examine the crystal structures and the morphologies of the prepared composites. Vibrating sample magnetometer was also used to reveal their superparamagnetic property. The UVVis spectrophotometer was employed to monitor the decomposition of methylene blue in the photocatalytic efficient study. It was found that at least a minimum thickness of the silica interlayer around 20 nm was necessary for the inhibition of electron transference initiated by TiO{sub 2} and MnZn ferrite.

  9. Moment mapping of body-centered-cubic Fe{sub x}Mn{sub 1−x} alloy films on MgO(001)

    SciTech Connect (OSTI)

    Idzerda, Y. U. Bhatkar, H.; Arenholz, E.

    2015-05-07

    The alloy composition and elemental magnetic moments of bcc single crystal films of compositionally graded Fe{sub x}Mn{sub 1−x} films (20 nm thick films with 0.8 ≤ x ≤ 0.9) grown on MgO(001) are spatially mapped using X-ray absorption spectroscopy and magnetic circular dichroism. Electron diffraction measurements on single composition samples confirmed that the structure of Fe{sub x}Mn{sub 1−x} films remained epitaxial and in the bcc phase from 0.65 ≤ x ≤ 1, but rotated 45° with respect to the MgO(001) surface net. This is beyond the bulk bcc stability limit of x = 0.88. The Fe moment is found to gradually reduce with increasing Mn content with a very abrupt decline at x = 0.85, a slightly higher composition than observed in the bulk. Surprisingly, the Mn exhibits a very small net moment (<0.1 μ{sub B}) at all compositions, suggesting a complex Mn spin structure.

  10. Kinetics of Mn-based sorbents for hot coal gas desulfurization. Quarterly report, December 15, 1993--March 15, 1997

    SciTech Connect (OSTI)

    Hepworth, M.T.

    1997-03-03

    Manganese-based sorbents have been investigated for the removal of hydrogen sulfide (the primary sulfur bearing compound) from hot coal gases prior to its use in combined cycle turbines. Four formulations of Mn-based sorbents were tested in an ambient-pressure fixed-bed reactor to determine steady state H{sub 2}S concentrations, breakthrough times and effectiveness of the sorbent when subjected to cyclic sulfidation and regeneration testing. In previous reports, the sulfidation and regeneration results from cyclic testing done at 600{degrees}C were presented. Manganese-based sorbents, with molar ratios > 1:1 Mn:Substrate were effective in reducing the H{sub 2}S concentration in simulated coal gases to less than 100 ppmv over five cycles. Actual breakthrough time for formulation C6-2-1100 was as high as 73% of breakthrough time based on wt% Mn in sorbent. Regeneration tests determined that loaded pellets can be fully regenerated in air/steam mixture at 750{degrees}C with minimal sulfate formation. In this report, the results from cyclic crush strength tests, Sulfur profile tests and cyclic testing at 550{degrees}C and lower flowrate cyclic testing are presented. Crush strength testing done after 5 cycles showed decreases in strength from 12.6% to 57.9%. Cyclic testing at 550{degrees}C showed pre breakthrough concentrations as low as 10 ppmv. Cyclic testing done at 2 L/min and 3 L/min did not show any significant difference in pre breakthrough concentrations or capacity.

  11. Temperature dependence of spin-orbit torque effective fields in the diluted magnetic semiconductor (Ga,Mn)As

    SciTech Connect (OSTI)

    Howells, B.; Edmonds, K. W.; Campion, R. P.; Gallagher, B. L.

    2014-07-07

    We report on a study of the temperature-dependence of current-induced effective magnetic fields due to spin-orbit interactions in the diluted ferromagnetic semiconductor (Ga,Mn)As. Contributions from the effective fields as well as from the anomalous Nernst effect are evident in the difference between transverse resistance measurements as a function of an external magnetic field for opposite orientations of the applied current. We separately extract these contributions by fitting to a model of coherently rotating magnetization. The component of the effective field with Dresselhaus symmetry is substantially enhanced with increasing temperature, while no significant temperature-dependence is observed for the component with Rashba symmetry.

  12. Proton pump inhibitors suppress iNOS-dependent DNA damage in Barrett's esophagus by increasing Mn-SOD expression

    SciTech Connect (OSTI)

    Thanan, Raynoo; Ma, Ning; Iijima, Katsunori; Abe, Yasuhiko; Koike, Tomoyuki; Shimosegawa, Tooru; Pinlaor, Somchai; Hiraku, Yusuke; Oikawa, Shinji; Murata, Mariko; Kawanishi, Shosuke

    2012-05-04

    Highlights: Black-Right-Pointing-Pointer Inflammation by Barrett's esophagus (BE) is a risk factor of its adenocarcinoma (BEA). Black-Right-Pointing-Pointer 8-Nitroguanine and 8-oxodG are inflammation-related DNA lesions. Black-Right-Pointing-Pointer DNA lesions and iNOS expression were higher in the order, BEA > BE > normal tissues. Black-Right-Pointing-Pointer Proton pump inhibitors suppress DNA damage by increasing Mn-SOD via Nrf2 activation. Black-Right-Pointing-Pointer DNA lesions can be useful biomarkers to predict risk of BEA in BE patients. -- Abstract: Barrett's esophagus (BE), an inflammatory disease, is a risk factor for Barrett's esophageal adenocarcinoma (BEA). Treatment of BE patients with proton pump inhibitors (PPIs) is expected to reduce the risk of BEA. We performed an immunohistochemical study to examine the formation of nitrative and oxidative DNA lesions, 8-nitroguanine and 8-oxo-7,8-dihydro-2 Prime -deoxygaunosine (8-oxodG), in normal esophageal, BE with pre- and post-treatment by PPIs and BEA tissues. We also observed the expression of an oxidant-generating enzyme (iNOS) and its transcription factor NF-{kappa}B, an antioxidant enzyme (Mn-SOD), its transcription factor (Nrf2) and an Nrf2 inhibitor (Keap1). The immunoreactivity of DNA lesions was significantly higher in the order of BEA > BE > normal tissues. iNOS expression was significantly higher in the order of BEA > BE > normal tissues, while Mn-SOD expression was significantly lower in the order of BEA < BE < normal tissues. Interestingly, Mn-SOD expression and the nuclear localization of Nrf2 were significantly increased, and the formation of DNA lesions was significantly decreased in BE tissues after PPIs treatment for 3-6 months. Keap1 and iNOS expression was not significantly changed by the PPIs treatment in BE tissues. These results indicate that 8-nitroguanine and 8-oxodG play a role in BE-derived BEA. Additionally, PPIs treatment may trigger the activation and nuclear translocation

  13. Effect of Heat-Treatment on the Phases of Ni-Mn-Ga Magnetic Shape Memory Alloys

    SciTech Connect (OSTI)

    Huq, Ashfia; Ari-Gur, Pnina; Kimmel, Giora; Richardson, James W; Sharma, Kapil

    2009-01-01

    The Heusler alloys Ni50Mn25+xGa25-x display magnetic shape memory effect (MSM) with very fast and large reversible strain under magnetic fields. This large strain and the speed of reaction make MSM alloys attractive as smart materials. Our crystallographic investigation of these alloys, focused on non-stoichiometric composition with excess of manganese. Using neutron diffraction, we revealed the necessary processing parameters to achieve and preserve the homogeneous metastable one-phase martensitic structure that is needed for an MSM effect at room temperature.

  14. Energy harvesting using martensite variant reorientation mechanism in a NiMnGa magnetic shape memory alloy

    SciTech Connect (OSTI)

    Karaman, I.; Basaran, B.; Karaca, H. E.; Karsilayan, A. I.; Chumlyakov, Y. I.

    2007-04-23

    Magnetic shape memory alloys demonstrate significant potential for harvesting waste mechanical energy utilizing the Villari effect. In this study, a few milliwatts of power output are achieved taking advantage of martensite variant reorientation mechanism in Ni{sub 51.1}Mn{sub 24}Ga{sub 24.9} single crystals under slowly fluctuating loads (10 Hz) without optimization in the power conversion unit. Effects of applied strain range, bias magnetic field, and loading frequency on the voltage output are revealed. Anticipated power outputs under moderate frequencies are predicted showing that the power outputs higher than 1 W are feasible.

  15. Octonary resistance states in La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 multiferroic tunnel junctions

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Yue -Wei Yin; Tao, Jing; Huang, Wei -Chuan; Liu, Yu -Kuai; Yang, Sheng -Wei; Dong, Si -Ning; Zhu, Yi -Mei; Li, Qi; Li, Xiao -Guang

    2015-10-06

    General drawbacks of current electronic/spintronic devices are high power consumption and low density storage. A multiferroic tunnel junction (MFTJ), employing a ferroelectric barrier layer sandwiched between two ferromagnetic layers, presents four resistance states in a single device and therefore provides an alternative way to achieve high density memories. Here, an MFTJ device with eight nonvolatile resistance states by further integrating the design of noncollinear magnetization alignments between the ferromagnetic layers is demonstrated. Through the angle-resolved tunneling magnetoresistance investigations on La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 junctions, it is found that, besides collinear parallel/antiparallel magnetic configurations, the MFTJ shows at least two other stable noncollinear (45°more » and 90°) magnetic configurations. As a result, combining the tunneling electroresistance effect caused by the ferroelectricity reversal of the BaTiO3 barrier, an octonary memory device is obtained, representing potential applications in high density nonvolatile storage in the future.« less

  16. Electrochemical performance of polyaniline coated LiMn{sub 2}O{sub 4} cathode active material for lithium ion batteries

    SciTech Connect (OSTI)

    ?ahan, Halil Dokan, Fatma K?l?c Ayd?n, Abdlhamit zdemir, Burcu zdemir, Nazl? Patat, ?aban

    2013-12-16

    LiMn{sub 2}O{sub 4} compound are synthesized by combustion method using glycine as a fuel at temperature (T), 800C which was coated by a polyaniline. The goal of this procedure is to promote better electronic conductivity of the LiMn{sub 2}O{sub 4} particles in order to improve their electrochemical performance for their application as cathodes in secondary lithium ion batteries. The structures of prepared products have been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). To investigate the effect of polyaniline coating galvanostatic charge-discharge cycling (148 mA g{sup ?1}) studies are made in the voltage range of 3.5-4.5 V vs. Li at room temperature. Electrochemical performance of the LiMn{sub 2}O{sub 4} was significantly improved by the polaniline coating.

  17. Self-assembly of compositionally modulated Ga{sub 1−x}Mn{sub x}As multilayers during molecular beam epitaxy

    SciTech Connect (OSTI)

    Gallardo-Hernández, S.; Martinez-Velis, I.; Ramirez-Lopez, M.; Lopez-Lopez, M.; Kudriatsev, Y.; Escobosa-Echavarria, A.; Luiz Morelhao, S.

    2013-11-04

    GaMnAs structures were grown on GaAs(100) substrates by molecular beam epitaxy employing different growth parameters. We studied manganese incorporation employing secondary ion mass spectrometry (SIMS). At a growth temperature of 300 °C, we observed a self-assembled modulation of the manganese concentration. SIMS depth profiles were analyzed employing a depth resolution function taking into account sputtering-induced broadening of the original distribution and segregation. We found a Mn segregation length along the growth direction of ∼4 nm. The presence of GaMnAs multilayers was corroborated by high-resolution x-ray diffraction. Spinodal decomposition is a possible mechanism for the spontaneous formation of the multilayer structure.

  18. Magnetooptical study of Zeeman effect in Mn modulation-doped InAs/InGaAs/InAlAs quantum well structures

    SciTech Connect (OSTI)

    Terent'ev, Ya. V.; Danilov, S. N.; Plank, H.; Loher, J.; Schuh, D.; Bougeard, D.; Weiss, D.; Ganichev, S. D.; Durnev, M. V.; Ivanov, S. V.; Tarasenko, S. A.; Rozhansky, I. V.; Yakovlev, D. R.

    2015-09-21

    We report on a magneto-photoluminescence (PL) study of Zeeman effect in Mn modulation-doped InAs/InGaAs/InAlAs quantum wells (QW). Two PL lines corresponding to the radiative recombination of photoelectrons with free and bound-on-Mn holes have been observed. In the presence of a magnetic field applied in the Faraday geometry, both lines split into two circularly polarized components. While temperature and magnetic field dependence of the splitting are well described by the Brillouin function, providing an evidence for exchange interaction with spin polarized manganese ions, the value of the splitting exceeds by two orders of magnitude the value of the giant Zeeman splitting estimated for the average Mn density in QW obtained by the secondary ion mass spectroscopy.

  19. A study of the phase transition and magnetocaloric effect in multiferroic La{sub 2}MnNiO{sub 6} single crystals

    SciTech Connect (OSTI)

    Balli, M. Jandl, S.; Fournier, P.; Gospodinov, M. M.

    2014-05-07

    Magnetic and magnetocaloric properties of single crystal double perovskite La{sub 2}MnNiO{sub 6} have been investigated in details. Its ordered phase with a high Curie temperature (T{sub C} = 280 K) exhibits a significant refrigerant capacity around room temperature. A model based on the mean field theory approximation has been used in order to quantify the magnetic and magnetocaloric properties in the ordered La{sub 2}MnNiO{sub 6}. The magnetization and entropy changes were satisfactorily simulated as a function of temperature and magnetic field. On the other hand, the presence of cationic disorder in La{sub 2}MnNiO{sub 6} phases allows to shift the Curie point to low temperature without a significant change in the magnetocaloric performance.

  20. Synthesis of Mn-intercalated layered titanate by exfoliation-flocculation approach and its efficient photocatalytic activity under visible-light

    SciTech Connect (OSTI)

    Fu, Jie; Tian, Yanlong; Chang, Binbin; Li, Gengnan; Xi, Fengna; Dong, Xiaoping

    2012-12-15

    A novel Mn-intercalated layered titanate as highly active photocatalyst in visible-light region has been synthesized via a convenient and efficient exfoliation-flocculation approach with divalent Mn ions and monolayer titanate nanosheets. The 0.91 nm interlayer spacing of obtained photocatalyst is in accordance with the sum of the thickness of titanate nanosheet and the diameter of Mn ions. The yellow photocatalyst shows a spectral response in visible-light region and the calculated band gap is 2.59 eV. The photocatalytic performance of this material was evaluated by degradation and mineralization of an aqueous dye methylene blue under visible-light irradiation, and an enhanced photocatalytic activity in comparison with protonated titanate as well as the P25 TiO{sub 2} and N-doped TiO{sub 2} was obtained. Additionally, the layered structure is retained, no dye ions intercalating occurs during the photocatalysis process, and a {approx}90% photocatalytic activity can be remained after reusing 3 cycles. - Graphical abstract: Mn-intercalated layered titanate as a novel and efficient visible-light harvesting photocatalyst was synthesized via a convenient and efficient exfoliation-flocculation approach in a mild condition. Highlights: Black-Right-Pointing-Pointer Mn-intercalated titanate has been prepared by exfoliation-flocculation approach. Black-Right-Pointing-Pointer The as-prepared catalyst shows spectral response in the visible-light region. Black-Right-Pointing-Pointer Heat treatment at certain temperature enables formation of Mn-doped TiO{sub 2}. Black-Right-Pointing-Pointer Dye can be degradated effectively by the catalyst under visible light irradiation.

  1. Design of Semiconducting Tetrahedral Mn 1 ₋ x Zn x O Alloys and Their Application to Solar Water Splitting

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Peng, Haowei; Ndione, Paul F.; Ginley, David S.; Zakutayev, Andriy; Lany, Stephan

    2015-05-18

    Transition metal oxides play important roles as contact and electrode materials, but their use as active layers in solar energy conversion requires achieving semiconducting properties akin to those of conventional semiconductors like Si or GaAs. In particular, efficient bipolar carrier transport is a challenge in these materials. Based on the prediction that a tetrahedral polymorph of MnO should have such desirable semiconducting properties, and the possibility to overcome thermodynamic solubility limits by nonequilibrium thin-film growth, we exploit both structure-property and composition-structure relationships to design and realize novel wurtzite-structure Mn₁₋xZnxO alloys. At Zn compositions above x ≈ 0.3, thin films ofmore » these alloys assume the tetrahedral wurtzite structure instead of the octahedral rocksalt structure of MnO, thereby enabling semiconductor properties that are unique among transition metal oxides, i.e., a band gap within the visible spectrum, a band-transport mechanism for both electron and hole carriers, electron doping, and a band lineup suitable for solar hydrogen generation. A proof of principle is provided by initial photo-electrocatalytic device measurements, corroborating, in particular, the predicted favorable hole-transport properties of these alloys.« less

  2. Magnetoresistance effects and spin-valve like behavior of an arrangement of two MnAs nanoclusters

    SciTech Connect (OSTI)

    Fischer, M.; Klar, P. J.; Elm, M. T.; Sakita, S.; Hara, S.

    2015-01-19

    We report on magnetotransport measurements on a MnAs nanocluster arrangement consisting of two elongated single-domain clusters connected by a metal spacer. The arrangement was grown on GaAs(111)B-substrates by selective-area metal organic vapor phase epitaxy. Its structural properties were investigated using scanning-electron microscopy and atomic-force microscopy, while its magnetic domain structure was analyzed by magnetic-force microscopy. The magnetoresistance of the arrangement was investigated at 120 K for two measurement geometries with the magnetic field oriented in the sample plane. For both geometries, discrete jumps of the magnetoresistance of the MnAs nanocluster arrangement were observed. These jumps can be explained by magnetic-field induced switching of the relative orientation of the magnetizations of the two clusters which affects the spin-dependent scattering in the interface region between the clusters. For a magnetic field orientation parallel to the nanoclusters' elongation direction a spin-valve like behavior was observed, showing that ferromagnetic nanoclusters may be suitable building blocks for planar magnetoelectronic devices.

  3. Effect of Pt and H{sub 2} on n-butane isomerization over Fe and Mn promoted sulfated zirconia

    SciTech Connect (OSTI)

    Song, Xuemin; Reddy, K.R.; Sayari, A.

    1996-06-01

    The activity of a 0.4 wt% Pt-containing Fe and Mn promoted sulfated zirconia (PtSFMZ) catalyst in n-butane isomerization at 35{degrees}C was compared to that of a Pt-free catalyst (SFMZ). The maximum rate of n-butane conversion observed in helium over PtSFMZ was found to be 2.5 times higher than that over the SFMZ catalyst under the same conditions. It is believed that n-butane isomerization proceeds via a bimolecular mechanism in which the formation of hydrogen-deficient intermediates (carbenium ions and butenes), is necessary and the presence of transition metals such as Pt, Fe, and Mn on sulfated zirconia facilitates the formation/accumulation of these intermediates and increases their stability on the catalyst surface. The presence of H{sub 2} had a strong negative effect on n-butane conversion over PtSFMZ, but had no effect over SFMZ. The negative effect of H{sub 2} on PtSFMZ catalyst in n-butane isomerization reaction was attributed to the decreased concentration of butenes in the presence of hydrogen atoms which are formed by the dissociation of H{sub 2} on Pt. The ability of calcined Pt-containing catalysts to activate hydrogen at 35{degrees}C was demonstrated. Reduced SFMZ with or without Pt was not active at 35{degrees}C regardless of the nature of the carrier gas. 42 refs., 5 figs.

  4. Ferromagnetic response of multiferroic TbMnO{sub 3} films mediated by epitaxial strain and chemical pressure

    SciTech Connect (OSTI)

    Izquierdo, J.; Morn, O.; Astudillo, A.; Bolaos, G.; Arnache, O.

    2014-05-07

    High quality Tb{sub 1?x}Al{sub x}MnO{sub 3} (x?=?0, 0.3) films have been grown under different values of compressive/tensile strain using (001)-oriented SrTiO{sub 3} and MgO substrates. The films were grown by means of rf sputtering at substrate temperature of 800??C. X-ray diffraction analysis shows that films are single phase, preferentially oriented in the (111) and (122) directions for films deposited on SrTiO{sub 3} and MgO substrates, respectively. Although the TbMnO{sub 3} target shows antiferromagnetic order, the films deposited on both substrates show weak ferromagnetic phase at low temperature coexisting with the antiferromagnetic phase. The introduction of Al in the films clearly enhances their ferromagnetic behavior, improving the magnetic performance of this material. Indeed, M(H) measurements at 5?K show a well-defined hysteresis for films grown on both substrates. However, a stronger magnetic signal (larger values of remanence and coercive field) is observed for films deposited on MgO substrates. The chemical pressure generated by Al doping together with the substrate-induced strain seem to modify the subtle competition between magnetic interactions in the system. It is speculated that such modification could lead to a non-collinear magnetic state that may be tuned by strain modifications. This may be performed by varying the thickness of the films and/or considering other substrate materials.

  5. Nano-twin Mediated Plasticity in Carbon-containing FeNiCoCrMn High Entropy Alloys

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Wu, Zhenggang; Bei, Hongbin; Parish, Chad M

    2015-06-14

    Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. Moreover, the effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. We found that these materials canmore » be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (~70% at 77 K and ~40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys.« less

  6. Kondo Effect in 3d-host Ferromagnetic Sm1-xCexMn2Ge2

    SciTech Connect (OSTI)

    Liang,G.; Yao, Q.; Xi, H.; Mochizuki, K.; Markert, J.; Croft, M.

    2006-01-01

    Lattice, Ce L{sub 3}-edge, magnetic susceptibility, and electrical resistivity results on polycrystalline Sm{sub 1-x}Ce{sub x}Mn{sub 2}Ge{sub 2} (0 {<=} x {<=} 1) compound series are presented. The lattice parameters a and c increase almost linearly with the increase of Ce concentration x. The Ce-L{sub 3} X-ray absorption spectra indicate that the Ce in this series is nearly trivalent, and Ce valence decreases slightly with the increase of Ce concentration x. Magnetic susceptibility results indicate that the antiferromagnetic (AF) phase in the re-entrant ferromagnetic compound, SmMn{sub 2}Ge{sub 2}, is completely destroyed by merely 1.1% Ce for Sm substitution. For x > 0.011, only ferromagnetic (FM) phases exist below room temperature. It is found that in these materials Ce Kondo scattering coexists with the 3d-host FM fields and is also effectively weakened by such fields.

  7. Magnetooptical study of CdSe/ZnMnSe semimagnetic quantum-dot ensembles with n-type modulation doping

    SciTech Connect (OSTI)

    Reshina, I. I. Ivanov, S. V.

    2014-12-15

    Magnetic and polarization investigations of the photoluminescence and resonant electron spin-flip Raman scattering in ensembles of self-organized CdSe/ZnMnSe semimagnetic quantum dots with n-type modulation doping are carried out. It is demonstrated that exciton transitions contribute to the photoluminescence band intensity, along with the transitions of trions in the singlet state. In the Hanle-effect measurements, negative circular polarization in zero magnetic field is observed, which is related to the optical orientation of a trion heavy hole. The lifetime and spin-relaxation time of a heavy hole are estimated as ?3 and ?1 ps, respectively. Such short times are assumed to be due to Auger recombination with the excitation of an intrinsic transition in a Mn{sup 2+} ion. Investigations of the photoluminescence-maximum intensity and shift in a longitudinal magnetic field at the ?{sup ?}?{sup +} and ?{sup ?}?{sup ?} polarizations reveal the pronounced spin polarization of electrons. Under resonant excitation conditions, a sharp increase in the photoluminescence-band maximum intensity at ?{sup ?} excitation polarization over the ?{sup +} one is observed. The Raman scattering peak at the electron spin-flip transition is observed upon resonant excitation in a transverse magnetic field in crossed linear polarizations. This peak is shown to be a Brillouin function of a magnetic field.

  8. Unconventional irreversible structural changes in a high-voltage Li–Mn-rich oxide for lithium-ion battery cathodes

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Mohanty, Debasish; Sefat, Athena S.; Payzant, E. Andrew; Li, Jianlin; Wood, David L.; Daniel, Claus

    2015-02-19

    Making all-electric vehicles (EVs) commonplace in transportation applications will require affordable high-power and high-energy-density lithium-ion batteries (LIBs). The quest for suitable cathode materials to meet this end has currently plateaued with the discovery of high-voltage (≥4.7 V vs. Li+), high capacity (~250 mAh/g) lithium–manganese-rich (LMR) layered composite oxides. In spite of the promise of LMR oxides in high-energy-density LIBs, an irreversible structural change has been identified in this work that is governed by the formation of a ‘permanent’ spin-glass type magnetically frustrated phase indicating a dominant AB2O4 (A = Li, B = Mn) type spinel after a short-term lithium deintercalationmore » (charging) and intercalation (discharging) process. Furthermore, reduction of transition metal (Mn) ions from the 4+ state (pristine LMR) to 3+ (cycled LMR), which alters the intercalation redox chemistry and suggests the presence of ‘unfilled’ lithium vacancies and/or oxygen vacancies in the lattice after cycling, has presented a major stumbling block. Finally, these situations result in both loss of capacity and fading of the voltage profile, and these combined effects significantly reduce the high energy density over even short-term cycling.« less

  9. Itinerant Antiferromagnetism in FeMnP0.8Si0.2

    SciTech Connect (OSTI)

    Sales, Brian C.; Susner, Michael A.; Conner, Benjamin S.; Yan, Jiaqiang Q.; May, Andrew F.

    2015-09-25

    Compounds based on the Fe2P structure have continued to attract interest because of the interplay between itinerant and localized magnetism in a noncentrosymmetric crystal structure, and because of the recent developments of these materials for magnetocaloric applications. We report the growth and characterization of millimeter-sized single crystals of FeMnP0.8Si0.2 with the Fe2P structure. Single-crystal x-ray diffraction, magnetization, resistivity, and Hall and heat capacity data are reported. The crystals exhibit itinerant antiferromagnetic order below 158 K with no hint of ferromagnetic behavior in the magnetization curves and with the spins ordered primarily in the ab plane. The room-temperature resistivity is close to the Ioffe-Regel limit for a metal. Single-crystal x-ray diffraction indicates a strong preference for Mn to occupy the larger pyramidal 3g site. The cation site preference in the as-grown crystals and the antiferromagnetism were not changed after high-temperature anneals and a rapid quench to room temperature

  10. Verification of Anderson superexchange in MnO via magnetic pair distribution function analysis and ab initio theory

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Benjamin A. Frandsen; Brunelli, Michela; Page, Katharine; Uemura, Yasutomo J.; Staunton, Julie B.; Billinge, Simon J. L.

    2016-05-11

    Here, we present a temperature-dependent atomic and magnetic pair distribution function (PDF) analysis of neutron total scattering measurements of antiferromagnetic MnO, an archetypal strongly correlated transition-metal oxide. The known antiferromagnetic ground-state structure fits the low-temperature data closely with refined parameters that agree with conventional techniques, confirming the reliability of the newly developed magnetic PDF method. The measurements performed in the paramagnetic phase reveal significant short-range magnetic correlations on a ~1 nm length scale that differ substantially from the low-temperature long-range spin arrangement. Ab initio calculations using a self-interaction-corrected local spin density approximation of density functional theory predict magnetic interactions dominatedmore » by Anderson superexchange and reproduce the measured short-range magnetic correlations to a high degree of accuracy. Further calculations simulating an additional contribution from a direct exchange interaction show much worse agreement with the data. Furthermore, the Anderson superexchange model for MnO is thus verified by experimentation and confirmed by ab initio theory.« less

  11. Galvanomagnetic properties of Fe{sub 2}YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    SciTech Connect (OSTI)

    Kourov, N. I. Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-15

    The Hall effect and the magnetoresistance of Fe{sub 2}YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit (H > 10 kOe), the value and the sign of the normal (R{sub 0}) and anomalous (R{sub s}) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R{sub s} in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio (R{sub s} ∝ ρ{sub 0}{sup 3.1}), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  12. Optical and magneto-optical studies of martensitic transformation in Ni-Mn-Ga magnetic shape memory alloys

    SciTech Connect (OSTI)

    Beran, L.; Cejpek, P.; Kulda, M.; Antos, R.; Holy, V.; Veis, M.; Straka, L.; Heczko, O.

    2015-05-07

    Optical and magneto-optical properties of single crystal of Ni{sub 50.1}Mn{sub 28.4}Ga{sub 21.5} magnetic shape memory alloy during its transformation from martensite to austenite phase were systematically studied. Crystal orientation was approximately along (100) planes of parent cubic austenite. X-ray reciprocal mapping confirmed modulated 10?M martensite phase. Temperature depended measurements of saturation magnetization revealed the martensitic transformation at 335?K during heating. Magneto-optical spectroscopy and spectroscopic ellipsometry were measured in the sample temperature range from 297 to 373?K and photon energy range from 1.2 to 6.5?eV. Magneto-optical spectra of polar Kerr rotation as well as the spectra of ellipsometric parameter ? exhibited significant changes when crossing the transformation temperature. These changes were assigned to different optical properties of Ni-Mn-Ga in martensite and austenite phases due to modification of electronic structure near the Fermi energy during martensitic transformation.

  13. Spin and orbital Ti magnetism at LaMnO3/SrTiO3 interfaces

    SciTech Connect (OSTI)

    Garcial-Barriocanal, J; Cezar, J. C.; Bruno, F. Y.; Thakur, P.; Brookes, N. B.; Utfeld, C.; Riviera-Calzada, A.; Giblin, S. R.; Taylor, J. W.; Duffy, J. A.; Dugdale, S. B.; Nakamura, T.; Kodama, K.; Leon, C.; Okamoto, Satoshi; Santamaria, J.

    2010-01-01

    In systems with strong electron-lattice coupling, such as manganites, orbital degeneracy is lifted, what causes a null expectation value of the orbital moment. Magnetic structure is thus determined by spin-spin superexchange. In titanates, however, with much smaller Jahn-Teller distortions, orbital degeneracy might allow non-zero values of the orbital magnetic moment. Accordingly, novel forms of ferromagnetic superexchange interaction unique to t2g electrons systems have been theoretically predicted, although their experimental observation has remained elusive. Here we report a new kind of Ti3+ ferromagnetism at LaMnO3/SrTiO3 epitaxial interfaces. It results from charge transfer to the empty conduction band of the titanate and has spin and orbital contributions evidencing the role played by orbital degeneracy. The possibility of tuning magnetic alignment (ferromagnetic or antiferromagnetic) of Ti and Mn moments by structural parameters is demonstrated. This result will provide important clues for the understanding of the effects of orbital degeneracy in superexchange coupling.

  14. Large magnetic entropy change and magnetoresistance in a Ni41Co9Mn40Sn10 magnetic shape memory alloy

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Huang, L.; Cong, D. Y.; Ma, L.; Nie, Z. H.; Wang, M. G.; Wang, Z. L.; Suo, H. L.; Ren, Y.; Wang, Y. D.

    2015-07-02

    A polycrystalline Ni41Co9Mn40Sn10 (at. %) magnetic shape memory alloy was prepared by arc melting and characterized mainly by magnetic measurements, in-situ high-energy X-ray diffraction (HEXRD), and mechanical testing. A large magnetoresistance of 53.8% (under 5 T) and a large magnetic entropy change of 31.9 J/(kg K) (under 5 T) were simultaneously achieved. Both of these values are among the highest values reported so far in Ni-Mn-Sn-based Heusler alloys. The large magnetic entropy change, closely related to the structural entropy change, is attributed to the large unit cell volume change across martensitic transformation as revealed by our in-situ HEXRD experiment. Furthermore,more » good compressive properties were also obtained. Lastly, the combination of large magnetoresistance, large magnetic entropy change, and good compressive properties, as well as low cost makes this alloy a promising candidate for multifunctional applications.« less

  15. Nano-twin Mediated Plasticity in Carbon-containing FeNiCoCrMn High Entropy Alloys

    SciTech Connect (OSTI)

    Wu, Zhenggang; Bei, Hongbin; Parish, Chad M

    2015-06-14

    Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. Moreover, the effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. We found that these materials can be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (~70% at 77 K and ~40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys.

  16. Heat capacity of the site-diluted spin dimer system Ba₃(Mn1-xVx)₂O₈

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Samulon, E. C.; Shapiro, M. C.; Fisher, I. R.

    2011-08-05

    Heat-capacity and susceptibility measurements have been performed on the diluted spin dimer compound Ba₃(Mn1-xVx)₂O₈. The parent compound Ba₃Mn₂O₈ is a spin dimer system based on pairs of antiferromagnetically coupled S=1, 3d² Mn⁵⁺ ions such that the zero-field ground state is a product of singlets. Substitution of nonmagnetic S=0, 3d⁰ V⁵⁺ ions leads to an interacting network of unpaired Mn moments, the low-temperature properties of which are explored in the limit of small concentrations 0≤x≤0.05. The zero-field heat capacity of this diluted system reveals a progressive removal of magnetic entropy over an extended range of temperatures, with no evidence for amore » phase transition. The concentration dependence does not conform to expectations for a spin-glass state. Rather, the data suggest a low-temperature random singlet phase, reflecting the hierarchy of exchange energies found in this system.« less

  17. Synthesis and electrochemical performance of high-capacity 0.34Li{sub 2}MnO{sub 3}0.66LiMn{sub 0.63}Ni{sub 0.24}Co{sub 0.13}O{sub 2} cathode materials using a CouetteTaylor reactor

    SciTech Connect (OSTI)

    Choi, Mansoo; Kim, Hyun-Soo; Kim, Jik-Soo; Park, Suk-Joon; Lee, Young Moo; Jin, Bong-Soo

    2014-10-15

    Highlights: The cathode material synthesized by co-precipitation using a CouetteTaylor reactor. The first and second discharge capacities were measured to be 311 and 307 mA h g{sup ?1}. The material has an excellent rate capability. - Abstract: The 0.34Li{sub 2}MnO{sub 3}0.66LiMn{sub 0.63}Ni{sub 0.24}Co{sub 0.13}O{sub 2} cathode material for the Li-ion battery is synthesized by co-precipitation using a CouetteTaylor reactor. Particle size analysis (PSA) and a field emission-scanning electron microscopy (FE-SEM) images show that the obtained precursor and cathode material exhibit a narrow particle size distribution and spherical shape. The structure and composition of the 0.34Li{sub 2}MnO{sub 3}0.66LiMn{sub 0.63}Ni{sub 0.24}Co{sub 0.13}O{sub 2} are confirmed by X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The first and second discharge capacities of 0.34Li{sub 2}MnO{sub 3}0.66LiMn{sub 0.63}Ni{sub 0.24}Co{sub 0.13}O{sub 2} are measured to be 311 and 307 mA h g{sup ?1}, respectively. The material also has an excellent rate capability (250 and 180 mA h g{sup ?1} at 1 C and 5 C, respectively). In the rate capability test at 60 C, 0.34Li{sub 2}MnO{sub 3}0.66LiMn{sub 0.63}Ni{sub 0.24}Co{sub 0.13}O{sub 2} has a higher capacity of over 210 mA h g{sup ?1} in the range 0.110 C. In the cyclic performance test, the capacity retention at high temperature is over 85% after 50 cycles, which is similar to that at room temperature. The 0.34Li{sub 2}MnO{sub 3}0.66LiMn{sub 0.63}Ni{sub 0.24}Co{sub 0.13}O{sub 2} is therefore a high-capacity material with potential for use as an electrode in Li-ion batteries.

  18. Thermal Variation of Ce Valence in Mixed ValenceKondo Lattice Systems CeT2(Si1-xGex)2 with T= Mn and Ni

    SciTech Connect (OSTI)

    Liang,G.; Croft, M.

    2008-01-01

    The results on the thermal variation of Ce L3-valence in CeT2(Si1-xGex)2 series with 0{le}x{le}1 and T=Mn and Ni are reported. It is observed that for both series, the Ce valence increases with decreasing temperature and has little thermal variation for samples in the nearly trivalent regime. The magnitude of this thermal variation in the T=Mn series is much greater than in the T=Ni series. The results are explained by the degenerate Anderson model and correlated with the specific heat data.

  19. Direct evidence on magnetic-field-induced phase transition in a NiCoMnIn ferromagnetic shape memory alloy under a stress field.

    SciTech Connect (OSTI)

    Wang, Y. D.; Ren, Y.; Huang, E. W.; Nie, Z. H.; Wang, G.; Liu, Y. D.; Deng, J. N.; Zuo, L.; Choo, H.; Liaw, P .K.; Brown, D. E.; Univ. of Tennessee; Northeastern Univ.; Northern Illinois Univ.

    2007-01-01

    The magnetoelasticity and magnetoplasticity behaviors of a Ni-Co-Mn-In ferromagnetic shape memory alloy (FSMA) induced by the reverse phase transformation interplayed under multiple (temperature, magnetic, and stress) fields were captured directly by high-energy synchrotron x-ray diffraction technique. The experiments showed the direct experimental evidence of that a stress ({approx}50 MPa) applied to this material made a complete recovery of the original orientations of the martensite variants, showing a full shape memory effect. This finding offers the in-depth understanding the fundamental properties and applications of the Ni-Co-Mn-In FSMA with the magnetic-field-induced reverse transformation.

  20. Direct evidence on magnetic-field-induced phase transition in a NiCoMnIn ferromagnetic shape memory alloy under a stress field

    SciTech Connect (OSTI)

    Wang, Y. D.; Ren Yang; Huang, E. W.; Nie, Z. H.; Wang, G.; Liu, Y. D.; Deng, J. N.; Zuo, L.; Choo, H.; Liaw, P. K.; Brown, D. E.

    2007-03-05

    The magnetoelasticity and magnetoplasticity behaviors of a Ni-Co-Mn-In ferromagnetic shape memory alloy (FSMA) induced by the reverse phase transformation interplayed under multiple (temperature, magnetic, and stress) fields were captured directly by high-energy synchrotron x-ray diffraction technique. The experiments showed the direct experimental evidence of that a stress ({approx}50 MPa) applied to this material made a complete recovery of the original orientations of the martensite variants, showing a full shape memory effect. This finding offers the in-depth understanding the fundamental properties and applications of the Ni-Co-Mn-In FSMA with the magnetic-field-induced reverse transformation.

  1. Direct observation of the structural and electronic changes of Li{sub 2}MnO{sub 3} during electron irradiation

    SciTech Connect (OSTI)

    Phillips, Patrick J.; Klie, Robert F. [Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607 (United States); Iddir, Hakim [Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States); Abraham, Daniel P. [Argonne National Laboratory, Chemical Sciences and Engineering, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States)

    2014-09-15

    This study focuses on the effects of electron beam induced irradiation to the layered oxide Li{sub 2}MnO{sub 3}. Aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy are used to characterize structural and electronic transitions in the material during irradiation, with a focus on changes in Mn valence and O content. This truly in situ irradiation allows for specific particle tracking, dose quantification, and real-time observation, while demonstrating many parallels to the oxide's structure evolution observed during electrochemical cycling. Furthermore, it is demonstrated that typical imaging conditions are not severe enough to induce damage to the pristine oxide.

  2. Order parameters and magnetocrystalline anisotropy of off-stoichiometric D0{sub 22} Mn{sub 2.36}Ga epitaxial films grown on MgO (001) and SrTiO{sub 3} (001)

    SciTech Connect (OSTI)

    Lee, Hwachol; Sukegawa, Hiroaki Mitani, Seiji; Hono, Kazuhiro

    2015-07-21

    We study the relationship between long range order parameters and the magnetocrystalline anisotropy of off-stoichiometric D0{sub 22} Mn{sub 2.36}Ga (MnGa) epitaxial films grown on MgO (001) and SrTiO{sub 3} (STO) (001) single crystalline substrates. MnGa films deposited on MgO (001) show rather large irregular variation in magnetization with increasing substrate temperature in spite of the improved long range order of total atomic sites. The specific site long range order of Mn-I site characterized in the [101] orientation revealed the fluctuation of the occupation fraction of two Mn atomic sites with elevated substrate temperature, which appears more relevant to the observed magnetization change than the long range order of the total atomic sites. In case of MnGa films grown on the lattice-matched STO (001), high long range order of the total atomic sites in spite of the existence of secondary phase represents that the lattice mismatch plays a crucial role in determining the atomic arrangement of Mn and Ga atoms in the off-stoichiometric compositional case of MnGa.

  3. Investigation of A-site La substituted BaTi{sub 0.96}Mn{sub 0.04}O{sub 3} ceramics: Searching for ferromagnetic origin

    SciTech Connect (OSTI)

    Gong, Gaoshang; Fang, Yujiao; Zerihun, Gebru; Yin, Chongyang; Huang, Shuai; Yuan, Songliu

    2014-06-28

    Ba{sub 1-x}La{sub x}Ti{sub 0.96}Mn{sub 0.04}O{sub 3} ceramics (x?=?0, 3%, 7%) were prepared by a modified Pechini method and the structure, morphology, magnetic and electric properties have been investigated. X-ray diffraction analysis reveals La{sup 3+} ions could suppress the formation of hexagonal phase effectively. The cell parameter c decreases firstly and then increases with the increase of La content, which indicates that La ions have been incorporated into the lattice of BaTi{sub 0.96}Mn{sub 0.04}O{sub 3}, and that Mn ions transform from high valence to low valence. The magnetization, polarization and leakage currents are also influenced by La doping greatly. Detailed analysis of magnetic variation with structural change attributes the room temperature ferromagnetism to double exchange interactions between Mn{sup 3+} and Mn{sup 4+} ions.

  4. Demonstration Assessment of Light-Emitting Diode (LED) Roadway Lighting at the I-35W Bridge, Minneapolis, MN

    SciTech Connect (OSTI)

    Kinzey, Bruce R.; Myer, Michael

    2009-08-31

    This report describes the process and results of a demonstration of solid-state lighting (SSL) technology conducted in 2009 at the recently reconstructed I-35W bridge in Minneapolis, MN. The project was supported under the U.S. Department of Energy (DOE) Solid-State Lighting GATEWAY Technology Demonstration Program. Other participants in the demonstration project included the Minnesota Department of Transportation (Mn/DOT), Federal Highways Administration (FHWA), and BetaLED™ (a division of Ruud Lighting). Pacific Northwest National Laboratory (PNNL) conducted the measurements and analysis of the results. DOE has implemented a three-year evaluation of the LED luminaires in this installation in order to develop new longitudinal field data on LED performance in a challenging, real-world environment. This document provides information through the initial phase of the I-35W bridge project, up to and including the opening of the bridge to the public and the initial feedback received on the LED lighting installation from bridge users. Initial findings of the evaluation are favorable, with minimum energy savings level of 13% for the LED installation relative to the simulated base case using 250W high-pressure sodium (HPS) fixtures. The LEDs had an average illuminance level of 0.91 foot candles compared to 1.29 fc for the HPS lamps. The LED luminaires cost $38,000 more than HPS lamps, yielding a lengthy payback period, however the bridge contractor had offered to include the LED luminaires as part of the construction package at no additional cost. One potentially significant benefit of the LEDs in this installation is avoiding rolling lane closures on the heavily-traveled interstate bridge for the purpose of relamping the HPS fixtures. Rolling lane closures involve multiple crew members and various maintenance and safety vehicles, diversion of traffic, as well as related administrative tasks (e.g., approvals, scheduling, etc.). Mn/DOT records show an average cost of

  5. Synthesis, structures, and properties of three Zn(II), Mn(II), and Cd(II) compounds based on tetrazole-1-acetic ligand

    SciTech Connect (OSTI)

    Liu, Dong-Sheng Chen, Wen-Tong; Xu, Ya-Ping; Shen, Ping; Hu, Shao-Jun; Sui, Yan

    2015-03-15

    Three new compounds, ([Zn(tza){sub 2}(H{sub 2}O)]·H{sub 2}O){sub n} (1), ([Mn(tza){sub 2}(Htza){sub 2}]·2H{sub 2}O){sub n} (2) and [Cd(tza){sub 2}]{sub n} (3), were obtained by reactions of 1H-Tetrazole-1-acetic (Htza) with corresponding metal salts, and characterized by elemental analysis, infrared spectroscopy, and single crystal X-ray diffraction, respectively. The X-ray diffraction analysis reveals that compound 1 is three-dimensional (3D) supramolecular structure with line chains. Compound 2 is three-dimensional (3D) supramolecular structure with Mn-carboxylate chains. Compound 3 is a 3D framework with (3,6)-connected ‘ant’ topological network. Furthermore, the photoluminescence of 1 and 3 and the magnetic properties of 2 have also been investigated. - Graphical abstract: Three new Zn/Mn/Cd compounds were obtained by reactions of Htza with corresponding metal salts, and characterized by chemical methods. Different linear chains result in different final structures. Compounds 1 and 2 are 3D supramolecular structures. Compound 3 is a 3D framework with (3,6)-connected ‘ant’ topological network. - Highlights: • Three new Zn/Mn/Cd compounds based on Htza ligand has been synthesized. • Different linear chains result in different final structures. • The fluorescence or magnetic properties have been investigated.

  6. Conversion of CH4 into H2 at 300 C using Pd/MnO2 catalyst made with an effect of water oxidation

    SciTech Connect (OSTI)

    Koyanaka, Hideki; Takeuchi, K; Kolesnikov, Alexander I

    2014-01-01

    A novel electricity-free deposition of palladium on the surface of manganese dioxide, which has a crystal structure of ramsdellite, was studied. Using the Pd deposition, a nano-particle of Pd/MnO2 was prepared, and it was used for a catalytic performance for reforming methane into hydrogen at 300 C.

  7. Preparation of LiMn{sub 2}O{sub 4} cathode thin films for thin film lithium secondary batteries by a mist CVD process

    SciTech Connect (OSTI)

    Tadanaga, Kiyoharu; Yamaguchi, Akihiro; Sakuda, Atsushi; Hayashi, Akitoshi; Tatsumisago, Masahiro; Duran, Alicia; Aparacio, Mario

    2014-05-01

    Highlights: LiMn{sub 2}O{sub 4} thin films were prepared by using the mist CVD process. An aqueous solution of lithium and manganese acetates is used for the precursor solution. The cell with the LiMn{sub 2}O{sub 4} thin films exhibited a capacity of about 80 mAh/g. The cell showed good cycling performance during 10 cycles. - Abstract: LiMn{sub 2}O{sub 4} cathode thin films for thin film lithium secondary batteries were prepared by using so-called the mist CVD process, employing an aqueous solution of lithium acetate and manganese acetate, as the source of Li and Mn, respectively. The aqueous solution of starting materials was ultrasonically atomized to form mist particles, and mists were transferred by nitrogen gas to silica glass substrate to form thin films. FE-SEM observation revealed that thin films obtained by this process were dense and smooth, and thin films with a thickness of about 750 nm were obtained. The electrochemical cell with the thin films obtained by sintering at 700 C exhibited a capacity of about 80 mAh/g, and the cell showed good cycling performance during 10 cycles.

  8. Dielectric relaxation and magnetodielectric response in DyMn{sub 0.5}Cr{sub 0.5}O{sub 3}

    SciTech Connect (OSTI)

    Yuan, B.; Yang, J. Zuo, X. Z.; Zhu, X. B.; Dai, J. M.; Song, W. H.; Kan, X. C.; Zu, L.; Sun, Y. P.

    2015-09-28

    We investigate the structural, magnetic, and magnetodielectric properties of DyMn{sub 0.5}Cr{sub 0.5}O{sub 3}. The sample can be indexed with an orthorhombic phase with B site disordered space group Pbnm. The valence state of both Mn and Cr ions are suggested to be +3 based on the results of x-ray photoelectron spectroscopy. Two thermally excited dielectric relaxation at temperatures T{sub N2} < T< 300 K and large magnetodielectric effect (MDC = 20%–30%) due to the disordered arrangement of Mn{sup 3+}/Cr{sup 3+} ions associated with electron hopping between them are observed. The absence of any noticeable magnetoresistance effect (MR < 0.5%) demonstrates that the observed magnetodielectric effect is an intrinsic behavior. These results suggest that DyMn{sub 0.5}Cr{sub 0.5}O{sub 3} is a magnetodielectric compound, whose dielectric properties are dependence of the applied magnetic field, which exhibits such effects near room temperature and holds great promise for future device applications.

  9. Effect of calcination temperature on electrical properties of Nd{sub 0.7}Ba{sub 0.3}MnO{sub 3}

    SciTech Connect (OSTI)

    Lim, K. P.; Halim, S. A.; Chen, S. K.; Ng, S. W.; Chew, Z. Y.

    2015-04-24

    In this work, Nd{sub 0.7}Ba{sub 0.3}MnO{sub 3} was synthesized via cryo-milling method to investigate the effect of calcination temperature on the structure, microstructure, magnetic and electrical properties. XRD analysis revealed all samples can be indexed to orthorhombic structure systems with Imma space group accompany with some minor phases of Mn{sub 2}O{sub 4} and BaMnO{sub 3}. FESEM analysis confirmed that a slight increase in the grain size from 117.4 nm (600C), 119.5 nm (700C), 121.0 nm (800C), 123.1 nm (900C) to 138.4 nm (1000C) was observed when different calcination temperature was applied. Four Point Probe measurements showed that all samples are in paramagnetic insulating region and T{sub MIT} is lower than 20K. Resistivity increase when grain size reduces due to increase of effective grain boundary that weakens the electron hopping process via double exchange mechanism. Beside, a drastic increase of resistivity also observed due to present of minor secondary phase (BaMnO{sub 3}) in sample C9.

  10. Heat capacity of the site-diluted spin dimer system Ba?(Mn1-xVx)?O?

    SciTech Connect (OSTI)

    Samulon, E. C.; Shapiro, M. C.; Fisher, I. R.

    2011-08-05

    Heat-capacity and susceptibility measurements have been performed on the diluted spin dimer compound Ba?(Mn1-xVx)?O?. The parent compound Ba?Mn?O? is a spin dimer system based on pairs of antiferromagnetically coupled S=1, 3d Mn?? ions such that the zero-field ground state is a product of singlets. Substitution of nonmagnetic S=0, 3d? V?? ions leads to an interacting network of unpaired Mn moments, the low-temperature properties of which are explored in the limit of small concentrations 0?x?0.05. The zero-field heat capacity of this diluted system reveals a progressive removal of magnetic entropy over an extended range of temperatures, with no evidence for a phase transition. The concentration dependence does not conform to expectations for a spin-glass state. Rather, the data suggest a low-temperature random singlet phase, reflecting the hierarchy of exchange energies found in this system.

  11. Point defects and p-type conductivity in Zn{sub 1x}Mn{sub x}GeAs{sub 2}

    SciTech Connect (OSTI)

    Kilanski, L.; Podgrni, A.; Dynowska, E.; Dobrowolski, W.

    2014-07-14

    Positron annihilation spectroscopy is used to study point defects in Zn{sub 1x}Mn{sub x}GeAs{sub 2} crystals with low Mn content 0?x?0.042 with disordered zincblende and chalcopyrite structure. The role of negatively charged vacancies and non-open-volume defects is discussed with respect to the high p-type conductivity with carrier concentration 10{sup 19}?p?10{sup 21}cm{sup ?3} in our samples. Neutral As vacancies, together with negatively charged Zn vacancies and non-open-volume defects with concentrations around 10{sup 16}?10{sup 18}cm{sup ?3}, are observed to increase with increasing Mn content in the alloy. The observed concentrations of defects are not sufficient to be responsible for the strong p-type conductivity of our crystals. Therefore, we suggest that other types of defects, such as extended defects, have a strong influence on the conductivity of Zn{sub 1x}Mn{sub x}GeAs{sub 2} crystals.

  12. Toward a better understanding of the magnetocaloric effect: An experimental and theoretical study of MnFe{sub 4}Si{sub 3}

    SciTech Connect (OSTI)

    Gourdon, Olivier; Gottschlich, Michael; Persson, Joerg; Cruz, Clarina de la; Petricek, Vaclav; McGuire, Michael A.; Brückel, Thomas

    2014-08-15

    The intermetallic compound MnFe{sub 4}Si{sub 3} has been studied by high-resolution Time of Flight (TOF) neutron powder diffraction. MnFe{sub 4}Si{sub 3} crystallizes in the hexagonal space group P6{sub 3}/mcm with lattice constants of a=b=6.8043(4) Å and c=4.7254(2) Å at 310 K. Magnetic susceptibility measurements show clearly the magnetic transition from paramagnetism to ferromagnetism at about 302(2) K. Magnetic structure refinements based on neutron powder diffraction data with and without external magnetic field reveal strong evidence on the origin of the large magnetocaloric effect (MCE) in this material as a partial reordering of the spins between ∼270 K and 300 K. In addition, electronic structure calculations using the self-consistent, spin-polarized Tight Binding-Linear MuffinTin Orbital (TB-LMTO) method were also accomplished to address the “coloring problem” (Mn/Fe site preference) as well as the unique ferromagnetic behavior of this intermetallic compound. - Graphical abstract: Theoretical and experimental reinvestigation of the magnetic structure of MnFe{sub 4}Si{sub 3} for a better understanding of its large magnetocaloric effect (MCE). - Highlights: • Strong magnetic transition from paramagnetism to ferromagnetism at about 302(2) K. • MCE associated to a partial reordering of the spins between ∼270 K and 300 K. • DFT calculations show strong relation between MCE and spintronic materials.

  13. Microstructural, magnetic, and optical properties of the self-assembled (III{sub 1-x}Mn{sub x})V quantum structure

    SciTech Connect (OSTI)

    Jeon, H. C.; Lee, S. J.; Kang, T. W.

    2010-01-04

    Diluted magnetic semiconductor (DMS) materials have attracted much attention because of the interest in both investigations of fundamental physical properties and promising applications for various spintronic devices. Among many DMS structures, (III{sub 1-x}Mn{sub x})V ferromagnetic semiconductor quantum structures have been particularly attractive due to their potential applications in spintronic devices and they have combined properties of both III-V semiconductors and Mn ferromagnetic compounds, and the excellent advantages derived by utilizing mature III-V based heterostructure technology. Even though not many papers have been reported on the formation of one layer of (III{sub 1-x}Mn{sub x})V Quantum structure-Quantum Dots(QDs) and Quantum Wires(Q-Wire), systematic studies concerning microstructural, magnetic, and optical properties of the (III{sub 1-x}Mn{sub x})V quantum structure have been more attractive because of the interest in promising applications in optoelectronic devices, such as spin injection lasers and spin switching devices.

  14. Design of Semiconducting Tetrahedral Mn1-xZnxO Alloys and Their Application to Solar Water Splitting

    SciTech Connect (OSTI)

    Peng, Haowei; Ndione, Paul F.; Ginley, David S.; Zakutayev, A.; Lany, Stephen

    2015-05-18

    Both structure-property and composition-structure relationships are exploited to design and realize novel wurtzite-structure Mn1-xZnxO alloys. A proof of principle is provided that corroborates, in particular, the predicted favorable hole-transport properties of these alloys.

  15. Unconventional Switching Behavior in La0.7Sr0.3MnO3/La0.7Sr0...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Unconventional Switching Behavior in La0.7Sr0.3MnO3La0.7Sr0.3CoO3 Exchange-spring Bilayer Monday, March 30, 2015 Interfacial magnetic interactions between ferromagnetic...

  16. Electric-field-induced strain effects on the magnetization of a Pr0.67Sr0.33MnO3 film

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zhang, B.; Sun, C. -J.; Lu, W.; Venkatesan, T.; Han, M. -G.; Zhu, Y.; Chen, J.; Chow, G. M.

    2015-05-26

    The electric-field control of magnetic properties of Pr0.67Sr0.33MnO3 (PSMO) film on piezoelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMNT) substrate was investigated. The piezoelectric response of the PMNT substrate to the electric field produced strain that was coupled to the PSMO film. The in-plane compressive (tensile) strain increased (decreased) the magnetization. The change of magnetic moment was associated with the Mn ions. First principle simulations showed that the strain-induced electronic redistribution of the two eg orbitals (3dz2 and 3dx2-y2) of Mn ions was responsible for the change of magnetic moment. This work demonstrates that the magnetoelectric effect in manganite/piezoelectric hetero-structures originates from the change inmore » eg orbital occupancy of Mn ions induced by strain rather than the interfacial effect.« less

  17. Ti-substituted tunnel-type Na0.44MnO2 oxide as a negative electrode for aqueous sodium-ion batteries

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Wang, Yuesheng; Liu, Jue; Lee, Byungju; Qiao, Ruimin; Yang, Zhenzhong; Xu, Shuyin; Yu, Xiqian; Gu, Lin; Hu, Yong-Sheng; Yang, Wanli; et al

    2015-03-25

    The aqueous sodium-ion battery system is a safe and low-cost solution for large-scale energy storage, due to the abundance of sodium and inexpensive aqueous electrolytes. Although several positive electrode materials, e.g., Na0.44MnO2, were proposed, few negative electrode materials, e.g., activated carbon and NaTi2(PO4)3, are available. Here we show that Ti-substituted Na0.44MnO2 (Na0.44[Mn1-xTix]O2) with tunnel structure can be used as a negative electrode material for aqueous sodium-ion batteries. This material exhibits superior cyclability even without the special treatment of oxygen removal from the aqueous solution. Atomic-scale characterizations based on spherical aberration-corrected electron microscopy and ab initio calculations are utilized to accuratelymore » identify the Ti substitution sites and sodium storage mechanism. Ti substitution tunes the charge ordering property and reaction pathway, significantly smoothing the discharge/charge profiles and lowering the storage voltage. Both the fundamental understanding and practical demonstrations suggest that Na0.44[Mn1-xTix]O2 is a promising negative electrode material for aqueous sodium-ion batteries.« less

  18. Study of the Mn-binding sites in photosystem II using antibodies raised against lumenal regions of the D1 and D2 reaction center proteins

    SciTech Connect (OSTI)

    Dalmasso, E.A.

    1992-04-01

    The experiments discussed in this thesis focus on identifying the protein segments or specific amino acids which provide ligands to the Mn cluster of photosystem II (PS II). This Mn cluster plays a central role in the oxygen-evolving complex (OEC) of PS II. The Mn cluster is thought to be bound by lumenal regions of the PS II reaction center proteins known as D1 and D2. First, several peptides were synthesized which correspond to specific lumenal segments of the D1 and D2 proteins. Next, polyclonal antibodies were successfully elicited using three of these peptides. The peptides recognized by these antibodies correspond to protein segments of the spinach reaction center proteins: Ile-321 to Ala-344 of D1 (D1-a), Asp-319 to Arg-334 of D1 (D1-b), and Val-300 to Asn-319 of D2 (D2-a). These antibodies were then used in assays which were developed to structurally or functionally probe the potential Mn-binding regions of the D1 and D2 proteins.

  19. Structural and magnetic characterization of the one-dimensional S = 5/2 antiferromagnetic chain system SrMn(VO4)(OH)

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Sanjeewa, Liurukara D.; Garlea, Vasile O.; McGuire, Michael A.; McMillen, Colin D.; Cao, Huibo; Kolis, Joseph W.

    2016-06-06

    The descloizite-type compound, SrMn(VO4)(OH), was synthesized as large single crystals (1-2mm) using a high-temperature high-pressure hydrothermal technique. X-ray single crystal structure analysis reveals that the material crystallizes in the acentric orthorhombic space group of P212121 (no. 19), Z = 4. The structure exhibits a one-dimensional feature, with [MnO4] chains propagating along the a-axis which are interconnected by VO4 tetrahedra. Raman and infrared spectra were obtained to identify the fundamental vanadate and hydroxide vibrational modes. Magnetization data reveal a broad maximum at approximately 80 K, arising from one-dimensional magnetic correlations with intrachain exchange constant of J/kB = 9.97(3) K between nearestmore » Mn neighbors and a canted antiferromagnetic behavior below TN = 30 K. Single crystal neutron diffraction at 4 K yielded a magnetic structure solution in the lower symmetry of the magnetic space group P21 with two unique chains displaying antiferromagnetically ordered Mn moments oriented nearly perpendicular to the chain axis. Lastly, the presence of the Dzyaloshinskii Moriya antisymmetric exchange interaction leads to a slight canting of the spins and gives rise to a weak ferromagnetic component along the chain direction.« less

  20. Thermochemistry of La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3} solid solutions (0

    SciTech Connect (OSTI)

    Kemik, Nihan; Takamura, Yayoi; Navrotsky, Alexandra

    2011-08-15

    The structure, the energetics and the internal redox reactions of La{sub 0.7}Sr{sub 0.3}Fe{sub x}Mn{sub 1-x}O{sub 3} have been studied in the complete solid solution range 0.0Mn) ratio. The balance between different valences of the transition metals, Mn and Fe, is the main factor in determining the energetics of the La{sub 0.70}Sr{sub 0.30}Fe{sub x}Mn{sub 1-x}O{sub 3} solid solution. - Graphical abstract: Enthalpy of mixing ({Delta}H{sub mix}) of La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3-{gamma}} solid solution at room temperature as a function of Fe/(Fe+Mn) ratio, x. Linear fits for the two regions at low and high x are shown as solid lines. The inset shows the content of Mn{sup 3+}, Mn{sup 4+}, Fe{sup 3+} and Fe{sup 4+} as a function of x based on the work by Jonker. The redox reactions between different valence states of Fe and Mn dominate the energetic behavior of the solid solution. Highlights: > Investigated the structure, the energetics and the internal redox reactions of La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3}. > Determined the formation and mixing enthalpy by high temperature oxide melt solution calorimetry. > Symmetry of the perovskite, transition metal valence and energetics are interdependent. > Thermochemical data shows convincing evidence of the interplay between the Mn{sup 4+} and the Fe{sup 4+} ions. > Balance between different valences of Mn and Fe dominates the energetics of La{sub 0.7}Sr{sub 0.3}Fe{sub x}Mn{sub 1-x}O{sub 3}.

  1. Magnetic properties of CeFe11-xCoxTi with ThMn12 structure

    SciTech Connect (OSTI)

    Zhou, C; Pinkerton, FE; Herbst, JF

    2014-05-07

    A series of novel alloys CeFe11-xCoxTi (0 <= x <= 11) with ThMn12 structure has been successfully prepared by melt-spinning. The Curie temperature T-c increases with Co content x, reaching a maximum of 689 degrees C at x = 9 and declining to 664 degrees C at complete Co filling (x = 11). The room temperature saturation magnetization 4 pi M-s and magnetocrystalline anisotropy H-a have been estimated by fitting the first quadrant demagnetization curve with the Stoner-Wohlfarth model. 4 pi M-s first increases with increasing Co up to x = 3, then decrease. H-a has a complex dependence on Co content, which is indicative of a change in the easy magnetization direction from axis to plane and back as the Co content increases. (C) 2014 AIP Publishing LLC.

  2. Neutron diffraction study of the magnetic-field-induced transition in Mn{sub 3}GaC

    SciTech Connect (OSTI)

    akir, .; Acet, M.; Farle, M.; Senyshyn, A.

    2014-01-28

    The antiperovskite Mn{sub 3}GaC undergoes an isostructural cubiccubic first order transition from a low-temperature, large-cell-volume antiferromagnetic state to a high-temperature, small-cell-volume ferromagnetic state at around 160?K. The transition can also be induced by applying a magnetic field. We study here the isothermal magnetic-field-evolution of the transition as ferromagnetism is stabilized at the expense of antiferromagnetism. We make use of the presence of the two distinct cell volumes of the two magnetic states as a probe to observe by neutron diffraction the evolution of the transition, as the external magnetic field carries the system from the antiferromagnetic to the ferromagnetic state. We show that the large-volume antiferromagnetic and the small-volume ferromagnetic states coexist in the temperature range of the transition. The ferromagnetic state is progressively stabilized as the field increases.

  3. Experimental and Numerical Analysis on the Distortion of Parts Made of 20MnCr5 by Hot Metal Forming

    SciTech Connect (OSTI)

    Rentsch, Ruediger; Brinksmeier, Ekkard [Stiftung Institut fuer Werkstofftechnik, Badgasteiner Strasse 3, 28359 Bremen (Germany)

    2011-05-04

    For high performance applications, shafts and gears made of 20MnCr5 (AISI 5120) are manufactured in large numbers every year. Inhomogeneities in the material properties, process perturbations and asymmetries in shape and operation setups provide a potential for the distortion of parts, often released by heat treatment. In this contribution experimental results on the distortion of shafts and the dishing of disk-like gear wheel blanks are presented. The numerical analysis of the hot-rolling process allowed to trace a peculiar segregation distribution at the cross-section of the bars back to the casting process, and to identify an asymmetric strain distribution which may be the main cause for shaft distortion. For the dishing of the disks a correlation to the resulting distribution of the material flow was found and, a process perturbation parameter identified which is assumed to be responsible for the observed material flow variation.

  4. Zero-field spin torque oscillation in Co{sub 2}(Fe, Mn)Si with a point contact geometry

    SciTech Connect (OSTI)

    Yamamoto, T. Kubota, T.; Yako, H.; Takanashi, K.; Seki, T.

    2015-03-02

    We show spin torque oscillation at zero external magnetic field using a point-contact giant magnetoresistance device with a highly spin-polarized Co{sub 2}Fe{sub 0.4}Mn{sub 0.6}Si (CFMS) Heusler alloy. The device emitted a high rf power (P{sub rf}) signal with a narrow spectral linewidth of 3?MHz without external magnetic field. Depending on the applied current, mode changes were clearly observed, and a large P{sub rf} of 25.7 nW was achieved. The large P{sub rf} and the high coherency of oscillation are attributable to the combination of the high spin-polarization of CFMS and the advantages of point-contact geometry.

  5. Pulsed high-magnetic-field experiments: New insights into the magnetocaloric effect in Ni-Mn-In Heusler alloys

    SciTech Connect (OSTI)

    Salazar Mejía, C. Nayak, A. K.; Felser, C.; Nicklas, M.; Ghorbani Zavareh, M.; Wosnitza, J.; Skourski, Y.

    2015-05-07

    The present pulsed high-magnetic-field study on Ni{sub 50}Mn{sub 35}In{sub 15} gives an extra insight into the thermodynamics of the martensitic transformation in Heusler shape-memory alloys. The transformation-entropy change, ΔS, was estimated from field-dependent magnetization experiments in pulsed high magnetic fields and by heat-capacity measurements in static fields. We found a decrease of ΔS with decreasing temperature. This behavior can be understood by considering the different signs of the lattice and magnetic contributions to the total entropy. Our results further imply that the magnetocaloric effect will decrease with decreasing temperature and, furthermore, the martensitic transition is not induced anymore by changing the temperature in high magnetic fields.

  6. 4D STUDY OF STRAIN GRADIENTS EVOLUTION IN TWINNED NiMnGa SINGLE CRYSTALS UNDER MAGNETIC FIELD

    SciTech Connect (OSTI)

    Barabash, Rozaliya; Xu, Ruqing; Barabash, Oleg M; Sozinov, Alexei

    2014-01-01

    Time-resolved 3D X-ray microscopy with a submicron beam size was used to follow the evolution of strains in off-stoichiometric NiMnGa twinned crystals near type I (hard) twin boundary under magnetic field. Laminate A/B microstructure was revealed near the twin boundaries in A variant. Large strain gradients are observed in the C variant in the immediate vicinity of the type I twin boundary: the lattice is under large tensile strains ~0.4% along the c- axes within first micron. Distinct a and b lattice parameter evolution with temperature and magnetic field is demonstrated. In an applied magnetic field the strain field was observed at larger distances from the twin boundary and becomes more complex. Stochastic twin boundary motion was observed after the magnetic field reaches a certain critical value.

  7. Experimental evidence of stress-field-induced selection of variants in Ni-Mn-Ga ferromagnetic shape-memory alloys

    SciTech Connect (OSTI)

    Wang, Y. D.; Brown, D. W.; Choo, H.; Liaw, P. K.; Benson, M. L.; Cong, D. Y.; Zuo, L.

    2007-05-01

    The in situ time-of-flight neutron-diffraction measurements captured well the martensitic transformation behavior of the Ni-Mn-Ga ferromagnetic shape-memory alloys under uniaxial stress fields. We found that a small uniaxial stress applied during phase transformation dramatically disturbed the distribution of variants in the product phase. The observed changes in the distributions of variants may be explained by considering the role of the minimum distortion energy of the Bain transformation in the effective partition among the variants belonging to the same orientation of parent phase. It was also found that transformation kinetics under various stress fields follows the scale law. The present investigations provide the fundamental approach for scaling the evolution of microstructures in martensitic transitions, which is of general interest to the condensed matter community.

  8. High power all-metal spin torque oscillator using full Heusler Co{sub 2}(Fe,Mn)Si

    SciTech Connect (OSTI)

    Seki, Takeshi Sakuraba, Yuya; Ueda, Masaki; Okura, Ryo; Takanashi, Koki; Arai, Hiroko; Imamura, Hiroshi

    2014-09-01

    We showed the high rf power (P{sub out}) emission from an all-metal spin torque oscillator (STO) with a Co{sub 2}Fe{sub 0.4}Mn{sub 0.6}Si (CFMS)/Ag/CFMS giant magnetoresistance (GMR) stack, which was attributable to the large GMR effect thanks to the highly spin-polarized CFMS. The oscillation spectra were measured by varying the magnetic field direction, and the perpendicular magnetic field was effective to increase P{sub out} and the Q factor. We simultaneously achieved a high output efficiency of 0.013%, a high Q of 1124, and large frequency tunability. CFMS-based all-metal STO is promising for overcoming the difficulties that conventional STOs are confronted with.

  9. Spin valves based on Mn{sub 75}Ir{sub 25} antiferromagnet with controllable functional parameters

    SciTech Connect (OSTI)

    Milyaev, M. A. Naumova, L. I.; Kamenskii, I. Yu.; Ustinov, V. V.

    2015-12-15

    Using the example of spin valves of the Ta(50 Å)/Ni{sub 80}Fe{sub 20}(30 Å)/Co{sub 90}Fe{sub 10}(15 Å)/Cu(28 Å)/Co{sub 90}Fe{sub 10}(20 Å)/Mn{sub 75}Ir{sub 25}(50 Å)/Ta(20 Å) composition, factors controlling the hysteresis properties are studied for the case of macro- and microscopic sizes of an experimental sample. It is shown that a linear change in the magnetoresistance with small hysteresis while retaining the giant magnetoresistance effect at a level of 8% can be obtained in a micro-object (meander) using thermomagnetic treatment.

  10. Bi–Mn mixed metal organic oxide: A novel 3d-6p mixed metal coordination network

    SciTech Connect (OSTI)

    Shi, Fa-Nian; Rosa Silva, Ana; Bian, Liang

    2015-05-15

    A new terminology of metal organic oxide (MOO) was given a definition as a type of coordination polymers which possess the feature of inorganic connectivity between metals and the direct bonded atoms and show 1D, 2D or 3D inorganic sub-networks. One such compound was shown as an example. A 3d-6p (Mn–Bi. Named MOOMnBi) mixed metals coordination network has been synthesized via hydrothermal method. The new compound with the molecular formula of [MnBi{sub 2}O(1,3,5-BTC){sub 2}]{sub n} (1,3,5-BTC stands for benzene-1,3,5-tricarboxylate) was characterized via single crystal X-ray diffraction technique that revealed a very interesting 3-dimensional (3D) framework with Bi{sub 4}O{sub 2}(COO){sub 12} clusters which are further connected to Mn(COO){sub 6} fragments into a 2D MOO. The topology study indicates an unprecedented topological type with the net point group of (4{sup 13}.6{sup 2})(4{sup 13}.6{sup 8})(4{sup 16}.6{sup 5})(4{sup 18}.6{sup 10})(4{sup 22}.6{sup 14})(4{sup 3}) corresponding to 3,6,7,7,8,9-c hexa-nodal net. MOOMnBi shows catalytic activity in the synthesis of (E)-α,β-unsaturated ketones. - Graphical abstract: This metal organic framework (MOF) is the essence of a 2D metal organic oxide (MOO). - Highlights: • New concept of metal organic oxide (MOO) was defined and made difference from metal organic framework. • New MOO of MOOMnBi was synthesized by hydrothermal method. • Crystal structure of MOOMnBi was determined by single crystal X-ray analysis. • The catalytic activity of MOOMnBi was studied showing reusable after 2 cycles.

  11. Influence of copper substitution on the magnetic and magnetocaloric properties of NiMnInB alloys

    SciTech Connect (OSTI)

    Pandey, Sudip Quetz, Abdiel; Aryal, Anil; Dubenko, Igor; Ali, Naushad; Samanta, Tapas; Stadler, Shane

    2015-05-07

    The structural, magnetocaloric, and thermomagnetic properties of Ni{sub 50.51}Mn{sub 34.34−x}Cu{sub x}In{sub 14.14}B{sub 1.01} with x = (0, 1.26, and 2.02) have been studied using room-temperature x-ray diffraction, differential scanning calorimetry (DSC), and magnetization measurements. The partial substitution of Cu for Mn was found to shift both the martensitic transition temperature (T{sub M}) and the Curie temperature (T{sub C}) to lower temperatures. The values of the latent heat (L = 9.4 J/g) and corresponding magnetic (ΔS{sub M}) and total entropy (ΔS{sub T}) changes (ΔS{sub M} = 22.60 J/kg K for ΔH = 5 T and ΔS{sub T} = 29.7 J/kg K) have been evaluated using magnetic and DSC measurements, respectively, for the sample with x = 1.26. Large negative values of ΔS{sub M} of −7.27 and −5.98 J/kg K for ΔH = 5 T in the vicinity of T{sub C} were observed for x = 1.26 and 2.02, respectively. It has been found that the application of hydrostatic pressure changes the magnetic ground state of the martensitic phase and increases the temperature stability of the martensitic phase. The roles of the magnetic and structural changes on the transition temperatures are discussed.

  12. Structural and magnetic properties of Sm{sub 2?x}Mn{sub x}O{sub 3} nanoparticles

    SciTech Connect (OSTI)

    Heiba, Zein K.; Mohamed, Mohamed Bakr; Fuess, H.

    2013-10-15

    Graphical abstract: - Highlights: C-type Sm{sub 2?x}Mn{sub x}O{sub 3} (0.0 ? x ?0.20) is prepared by solgel method. A maximum solubility of x = 0.15 is confirmed by X-ray diffraction, Raman and infrared techniques. Samples with x > 0.05 exhibit weak ferromagnetic properties; for x ? 0.05 antiferromagnetic behaviors is obtained. Correlation between magnetic behaviors and structural and microstructural parameters is discussed. - Abstract: Mixed oxide Sm{sub 2?x}Mn{sub x}O{sub 3} (SMO), x = 0.0, 0.05, 0.10, 0.15 and 0.20 were synthesized by a solgel process. A single phase solid solution is formed up to x = 0.15 which confirmed by using X-ray diffraction, Raman spectroscopy and infrared techniques. Crystal structure and microstructure analyses were performed by Rietveld refinement. Preferential cationic distribution, over the two crystallographic sites 8b and 24d of space group Ia3{sup }, is found for doped samples but with different extent. The r.m.s. microstrain ??{sub L}{sup 2}?{sup 1/2} depends on composition x in a systematic way emphasizing the preferential distribution. Magnetization measurements show that samples with x ? 0.05 have antiferromagnetic behavior, while samples with x > 0.05 exhibit a weak ferromagnetic behavior with magnetic phase transformation at 15 and 16 K for x = 0.1 and x = 0.15, respectively.

  13. Nuclear and magnetic supercells in the multiferroic candidate: Pb{sub 3}TeMn{sub 3}P{sub 2}O{sub 14}

    SciTech Connect (OSTI)

    Silverstein, Harlyn J.; Huq, Ashfia; Lee, Minseong; Choi, Eun Sang; Zhou, Haidong; Wiebe, Christopher R.

    2015-01-15

    The dugganites, Te{sup 6+}-containing members of the langasite series, have attracted recent interest due to their complex low-temperature magnetic unit cells, magnetodielectric, and potentially multiferroic properties. For Pb{sup 2+}-containing dugganites, a large monoclinic supercell was reported and was found to have a profound effect on the low temperature magnetism and spin excitation spectra. Pb{sub 3}TeMn{sub 3}P{sub 2}O{sub 14} is another dugganite previously shown to distort away from the canonical P321 langasite unit cell, although this supercell was never fully solved. Here we report the full crystal and magnetic structure solution of Pb{sub 3}TeMn{sub 3}P{sub 2}O{sub 14} using synchrotron x-ray and neutron diffraction data: a large trigonal supercell is observed in this material, which is believed to be the first supercell of its kind in the langasite family. Here, the magnetic structure, high-magnetic field behavior, and dielectric properties of Pb{sub 3}TeMn{sub 3}P{sub 2}O{sub 14} are presented. In addition to showing weak magnetoelectric behavior similar to other langasites, it was found that a phase transition occurs at 3 T near the antiferromagnetic transition temperature. - Graphical abstract: The nuclear supercell of Pb{sub 3}TeMn{sub 3}P{sub 2}O{sub 14}, found through joint refinements using high resolution synchrotron X-ray and neutron powder diffraction, retains the trigonal symmetry of the subcell. - Highlights: • Large P3 supercell found in Pb{sub 3}TeMn{sub 3}P{sub 2}O{sub 14}. • Complex helical spin structures below T{sub N}=6.6 K. • Phase transition at 3 T found using through dielectric and DC susceptibility measurements. • Moment saturation near 25 T at 1.4 K.

  14. Temperature dependent evolution of the electronic and local atomic structure in the cubic colossal magnetoresistive manganite La1-xSrxMnO3

    SciTech Connect (OSTI)

    Arenholz, Elke; Mannella, N.; Booth, C.H.; Rosenhahn, A.; Sell, B.C.; Nambu, A.; Marchesini, S.; Mun, B. S.; Yang, S.-H.; Watanabe, M.; Ibrahim, K.; Arenholz, E.; Young, A.; Guo, J.; Tomioka, Y.; Fadley, C.S.

    2007-12-06

    We have studied the temperature-dependent evolution of the electronic and local atomic structure in the cubic colossal magnetoresistive manganite La{sub 1-x}Sr{sub x}MnO{sub 3} (x= 0.3-0.4) with core and valence level photoemission (PE), x-ray absorption spectroscopy (XAS), x-ray emission spectroscopy (XES), resonant inelastic x-ray scattering (RIXS), extended x-ray absorption fine structure (EXAFS) spectroscopy and magnetometry. As the temperature is varied across the Curie temperature T{sub c}, our PE experiments reveal a dramatic change of the electronic structure involving an increase in the Mn spin moment from {approx} 3 {micro}B to {approx} 4 {micro}B, and a modification of the local chemical environment of the other constituent atoms indicative of electron localization on the Mn atom. These effects are reversible and exhibit a slow-timescale {approx}200 K-wide hysteresis centered at T{sub c}. Based upon the probing depths accessed in our PE measurements, these effects seem to survive for at least 35-50 {angstrom} inward from the surface, while other consistent signatures for this modification of the electronic structure are revealed by more bulk sensitive spectroscopies like XAS and XES/RIXS. We interpret these effects as spectroscopic fingerprints for polaron formation, consistent with the presence of local Jahn-Teller distortions of the MnO{sub 6} octahedra around the Mn atom, as revealed by the EXAFS data. Magnetic susceptibility measurements in addition show typical signatures of ferro-magnetic clusters formation well above the Curie temperature.

  15. Electronic and optical properties of ScN and (Sc,Mn)N thin films deposited by reactive DC-magnetron sputtering

    SciTech Connect (OSTI)

    Saha, Bivas; Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 ; Naik, Gururaj; Boltasseva, Alexandra; School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 ; Drachev, Vladimir P.; School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907; Department of Physics, University of North Texas, Denton, Texas 76203 ; Marinero, Ernesto E.; Sands, Timothy D.; Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907; School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907

    2013-08-14

    Scandium nitride (ScN) is a rocksalt semiconductor that has attracted significant attention from various researchers for a diverse range of applications. Motivated by the prospect of using its interesting electronic structure for optoelectronic and dilute magnetic semiconductor applications, we present detailed studies of the electronic transport and optical properties of ScN and its alloys with manganese nitride (MnN). Our results suggest (a) dilute manganese doping in ScN compensates for the high n-type carrier concentrations arising due to oxygen impurities and (b) an n-type to p-type carrier type transition occurs at a composition between 5.8% and 11% Mn on Sc sites. In terms of its optical properties, our analysis clearly indicates direct and indirect bandgap absorption edges of ScN located at 2.04 eV and 1.18 eV, respectively. In addition to the direct gap absorption edge, (Sc,Mn)N samples also show Mn-defect induced electronic absorption. Photoluminescence measurements at room temperature from ScN films exhibit a yellowish-green emission corresponding to direct gap radiative recombination. Direct gap recombination is not expected given the smaller indirect gap. A possible role of high excitation intensities in suppressing relaxation and recombination across the indirect bandgap is suspected. Raman spectroscopic and ellipsometric characterization of the dielectric permittivities of ScN and (Sc,Mn)N are also presented to assist in understanding the potential of ScN for optoelectronic applications.

  16. Magnetic field-induced phase transformation in NiMnCoIn magnetic shape memory alloys - a new actuation mechanism with large work output.

    SciTech Connect (OSTI)

    Karaca, H. E.; Karaman, I.; Basaran, B.; Ren, Y.; Chumlyakov, Y. I.; Maier, H. J.; X-Ray Science Division; Texsas A&M Univ.; Univ. of Kentucky; Siberian Physical-Technical Inst.; Univ. of Paderborn

    2009-04-09

    Magnetic shape memory alloys (MSMAs) have recently been developed into a new class of functional materials that are capable of magnetic-field-induced actuation, mechanical sensing, magnetic refrigeration, and energy harvesting. In the present work, the magnetic field-induced martensitic phase transformation (FIPT) in Ni{sub 45}Mn{sub 36.5}Co{sub 5}In{sub 13.5} MSMA single crystals is characterized as a new actuation mechanism with potential to result in ultra-high actuation work outputs. The effects of the applied magnetic field on the transformation temperatures, magnetization, and superelastic response are investigated. The magnetic work output of NiMnCoIn alloys is determined to be more than 1 MJ m{sup -3} per Tesla, which is one order of magnitude higher than that of the most well-known MSMAs, i.e., NiMnGa alloys. In addition, the work output of NiMnCoIn alloys is orientation independent, potentially surpassing the need for single crystals, and not limited by a saturation magnetic field, as opposed to NiMnGa MSMAs. Experimental and theoretical transformation strains and magnetostress levels are determined as a function of crystal orientation. It is found that [111]-oriented crystals can demonstrate a magnetostress level of 140 MPa T{sup -1} with 1.2% axial strain under compression. These field-induced stress and strain levels are significantly higher than those from existing piezoelectric and magnetostrictive actuators. A thermodynamical framework is introduced to comprehend the magnetic energy contributions during FIPT. The present work reveals that the magnetic FIPT mechanism is promising for magnetic actuation applications and provides new opportunities for applications requiring high actuation work-outputs with relatively large actuation frequencies. One potential issue is the requirement for relatively high critical magnetic fields and field intervals (1.5-3 T) for the onset of FIPT and for reversible FIPT, respectively.

  17. Preparation and structural, optical, magnetic, and electrical characterization of Mn{sup 2+}/Co{sup 2+}/Cu{sup 2+} doped hematite nanocrystals

    SciTech Connect (OSTI)

    Srikrishna Ramya, S.I. Mahadevan, C.K.

    2014-03-15

    Pure and Mn{sup 2+} / Co{sup 2+} / Cu{sup 2+} doped (1 and 2 at.%) spherical hematite (α-Fe{sub 2}O{sub 3})nanocrystals have been synthesized by a simple solvothermal method using a domestic microwave oven. XRD measurements confirm that all the seven nanocrystals prepared consist of nanocrystalline hematite phase without any other phases. The energy dispersive X-ray and Fourier transform infrared spectral analyses confirm the phase purity of the nanocrystals prepared. TEM analysis shows the average particle sizes within the range 33–51 nm. Optical absorption measurements indicate that all the three dopants enhance the optical transmittance and reflectance. A red shift is observed in the bandgap energy values estimated from optical absorption and reflectance spectra. Results of magnetic measurements made at room temperature using a vibrating sample magnetometer indicate significant changes in the magnetic properties (coercivity, retentivity and saturationmagnetization) due to doping. Results of magnetic measurements indicate significant changes in the magnetic properties. Results of AC electrical measurements made at various temperatures in the range 40–130 °C and frequencies in the range 100 Hz –1 MHz indicate low dielectric constants and AC electrical conductivities and consequently show the occurrence of nanoconfined states. -- Graphical abstract: The indexed X-ray diffraction (XRD) patterns of all the seven nanocrystals indicate the rhombohedral structure of hematite (JCPDS card No.13-0534). No impurity phase like oxides of Mn or Co or Cu was detected above equipment limit. The average crystallite (grain) sizes estimated using the Scherrer's formula. Highlights: • Pure and Mn/Co/Cu-doped hematite nanocrystals have been prepared. • The method adopted for the preparation is simple, economical and scalable. • Prepared nanocrystals are spherical in shape with good crystallinity and phase purity. • Mn/Co/Cu-doping enhances the optical transmittance

  18. The effects of annealing on the microstructure and mechanical properties of Fe28Ni18Mn33Al21

    SciTech Connect (OSTI)

    Meng, Fanling; Qiu, Jingwen; Baker, Ian; Bei, Hongbin

    2015-08-20

    In this paper, As-cast Fe28Ni18Mn33Al21, which consists of aligned, 50 nm, (Ni, Al)-rich B2, and (Fe, Mn)-rich f.c.c. phases, was annealed at a variety of temperatures up to 1423 K and the microstructure and mechanical properties were examined. It was shown that the as-cast microstructure arises from a eutectoid transformation at ~1300 K. Annealing at temperatures ≤1073 K produces β-Mn-structured precipitates and hardness values up to 816 HV, while annealing at temperatures >1073 K leads to dramatic coarsening of the two-phase B2/f.c.c. microstructure (up to 5.5 µm after 50 h at 1273 K), but does not lead to β-Mn precipitation. Interestingly, annealing at temperatures >1073 K delays the onset of β-Mn precipitation during subsequent anneals at lower temperatures. Coarsening the B2/f.c.c. lamellar structure by annealing at higher temperatures softens it and leads to increases in ductility from fracture before yield to ~8 % elongation. Finally, the presence of β-Mn precipitates makes the very fine, brittle B2/f.c.c. microstructures even more brittle, but significant ductility (8.4 % elongation) is possible even with β-Mn precipitates present if the B2/f.c.c. matrix is coarse and, hence, more ductile.

  19. Study of C-coated LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} as positive electrode material for Li-ion batteries

    SciTech Connect (OSTI)

    Perea, A.; Castro, L.; Aldon, L.; Stievano, L.; Dedryvere, R.; Gonbeau, D.; Tran, N.; Nuspl, G.; Breger, J.; Tessier, C.

    2012-08-15

    Commercial C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} positive electrode material has been investigated by {sup 57}Fe Moessbauer Spectroscopy (MS), X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The combined use of these experimental techniques provides a better understanding of the electrochemical reaction involved during cycling. {sup 57}Fe MS is very efficient to directly follow oxidation state of Fe in the electrode, and gives surprisingly indirect information on the oxidation state of Mn as observed by XAS and XPS. The electrochemical mechanism is proposed based from in situ and operando investigations using both MS and XAS, and is consistent with XPS surface studies. XPS analysis of the electrodes at the end of charge (4.4 V) reveals enhanced electrode/electrolyte interface reactivity at this high potential. Aging of C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4}/Li cells after 50 cycles at 60 Degree-Sign C indicates a rather good electrochemical behavior (low capacity fading) of the electrode material. Both {sup 57}Fe MS and XPS (Mn 2p and Fe 2p) clearly show no modification on Fe and Mn oxidation state compared to fresh electrode confirming the good electrochemical performances. - Graphical abstrct: Quantitative evaluation of the Fe{sup 3+} and Mn{sup 3+} content during the first charge/discharge cycle obtained from K-edge XANES spectra of C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} recorded upon cell operation at RT with C/10 rate. During the charge co-existence of Fe and Mn oxidation is observed between points 2 and 4 of the potential curve. At the end of the charge the cut-off voltage limits the oxidation at about 93%. Highlights: Black-Right-Pointing-Pointer C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} electrode material upon cycling vs. metallic lithium. Black-Right-Pointing-Pointer {sup 57}Fe Moessbauer spectroscopy is a (in)direct probe for Fe(Mn) oxidation state. Black-Right-Pointing-Pointer Both K-Fe and K-Mn edges XAS show a simultaneous

  20. Kondo Lattice Behavior in the Ordered Dilute Magnetic Semiconductor Yb14-xLaxMnSb11

    SciTech Connect (OSTI)

    Sales, Brian C; Khalifah, Peter; Enck, Thomas P; Nagler, Evan J; Sykora, Richard E; Jin, Rongying; Mandrus, David

    2005-01-01

    We report Hall, magnetic, heat capacity, and doping studies from single crystals of Yb{sub 14}MnSb{sub 11} and Yb{sub 13.3}La{sub 0.7}MnSb{sub 11}. These heavily doped semiconducting compounds are ferromagnetic below 53 and 39 K, respectively. The renormalization of the carrier mass from 2m{sub 3} near room temperature to 20m{sub e} at 5 K, plus the magnetic evidence for partial screening of the Mn magnetic moments suggest that these compounds represent rare examples of an underscreened Kondo lattice with T{sub K} {approx} 285 K.

  1. Substitution effect on the magnetic and transport properties of CeNi{sub 0.8−x}Mn{sub x}Bi{sub 2}

    SciTech Connect (OSTI)

    Kim, Soo-Whan; Lee, Kyujoon; Jung, Myung-Hwa; Adroja, D. T.; Demmel, F.; Taylor, J. W.

    2014-08-21

    We report the results of Mn substitution for Ni in CeNi{sub 0.8}Bi{sub 2} (i.e., CeNi{sub 0.8−x}Mn{sub x}Bi{sub 2}). All the samples have an antiferromagnetic ordered state below T{sub N} = 5.0 K due to localized 4f-magnetic moment on the Ce ions. Besides this antiferromagnetic ordering caused by Ce, the magnetic and transport properties are abruptly changed with increasing Mn contents at the boundary composition of x = 0.4. The magnetic state is changed into a ferromagnetic state around 200 K for x > 0.4, where the electrical resistivity is strongly suppressed to become simple metallic. These results of ferromagnetism and metallicity can be explained by the double exchange mechanism, rather than the simple picture of Doniach phase diagram. The mixed valence states of Ni and Mn ions are confirmed by X-ray photoelectron spectroscopy. For x ≤ 0.4, the initial Ni{sup 3+} state gradually changes to the Ni{sup 2+} state with increasing x up to 0.4. On further increase of x > 0.4, the Ni{sup 2+} state is replaced by the Mn{sup 2+} state, which gradually changes to the final Mn{sup 3+} state. We also present an inelastic neutron scattering (INS) measurements on CeNi{sub 0.8}Bi{sub 2} (i.e., x = 0) between 1.2 and 12 K. The high energy INS study reveals the presence of two well-defined crystal electric field (CEF) excitations near 9 meV and 19 meV at 1.2 K and 6 K, while the low energy INS study reveals the presence of quasielastic scattering above 4 K. We will discuss our INS results of CeNi{sub 0.8}Bi{sub 2} based on the CEF model.

  2. Magnetic ordering in TbMn{sub 0.5}Cr{sub 0.5}O{sub 3} studied by neutron diffraction and first-principles calculations

    SciTech Connect (OSTI)

    Staruch, M.; Sharma, V.; Ramprasad, R.; Cruz, C. dela; Jain, M.

    2014-07-21

    The structure and magnetic ordering of bulk TbMn{sub 0.5}Cr{sub 0.5}O{sub 3} was revealed through bulk magnetization and neutron diffraction measurements, and first-principles calculations, respectively. G-type antiferromagnetic ordering of Mn{sup 3+} and Cr{sup 3+} moments was observed in the neutron diffraction data below Nel temperature T{sub N}???84?K. In addition, below ?40?K, short-range magnetic ordering was identified correlating to a ferromagnetic component due to the canting of the moments along the c-axis. The spin configuration is consistent with the first-principles calculations. The magnetic structure revealed in the present TbMn{sub 0.5}Cr{sub 0.5}O{sub 3} sample is distinct from that observed for both end members TbMnO{sub 3} and TbCrO{sub 3}.

  3. HYPERFINE-DEPENDENT gf-VALUES OF Mn I LINES IN THE 1.49-1.80 ?m H BAND

    SciTech Connect (OSTI)

    Andersson, M.; Hutton, R.; Zou, Y. [The Key Lab of Applied Ion Beam Physics, Ministry of Education (China); Grumer, J.; Brage, T. [Division of Mathematical Physics, Department of Physics, Lund University (Sweden); Ryde, N.; Blackwell-Whitehead, R. [Department of Astronomy and Theoretical Physics, Lund University (Sweden); Jnsson, P., E-mail: rhutton@fudan.edu.cn [School of Technology, Malm University (Sweden)

    2015-01-01

    The three MnI lines at 17325, 17339, and 17349 are among the 25 strongest lines (log (gf) > 0.5) in the Hband. They are all heavily broadened due to hyperfine structure, and the profiles of these lines have so far not been understood. Earlier studies of these lines even suggested that they were blended. In this work, the profiles of these three infrared (IR) lines have been studied theoretically and compared to experimental spectra to assist in the complete understanding of the solar spectrum in the IR. It is shown that the structure of these lines cannot be described in the conventional way using the diagonal A and B hyperfine interaction constants. The off-diagonal hyperfine interaction not only has a large impact on the energies of the hyperfine levels, but also introduces a large intensity redistribution among the hyperfine lines, changing the line profiles dramatically. By performing large-scale calculations of the diagonal and off-diagonal hyperfine interaction and the gf-values between the upper and lower hyperfine levels and using a semi-empirical fitting procedure, we achieved agreement between our synthetic and experimental spectra. Furthermore, we compare our results with observations of stellar spectra. The spectra of the Sun and the K1.5 III red giant star Arcturus were modeled in the relevant region, 1.73-1.74 ?m, using our theoretically predicted gf-values and energies for each individual hyperfine line. Satisfactory fits were obtained and clear improvements were found using our new data compared with the old available MnI data. A complete list of energies and gf-values for all the 3d {sup 5}4s({sup 7} S)4d e{sup 6}D - 3d {sup 5}4s({sup 7} S)4f w{sup 6}F hyperfine lines are available as supporting material, whereas only the stronger lines are presented and discussed in detail in this paper.

  4. Synthesis and catalytic application of nanofibrous La{sub 0.9}A{sub 0.1}MnO{sub 3} (A = Ca, Cu, Ag) with macroscopic shapes

    SciTech Connect (OSTI)

    Wu, Qiang Zhao, Li; Wu, Jiang; Yao, Weifeng

    2013-10-15

    Graphical abstract: Fabrication of nanofibrous La{sub 0.9}A{sub 0.1}MnO{sub 3} (A = Ca, Cu, Ag) perovskite-type oxides with macroscopic shapes was successfully obtained using carbon nanofibers (CNFs) as templates. Furthermore, their application for the combustion of carbon black (CB), which is a model of particulate matter exhausted from diesel engines, was demonstrated. - Highlights: Nanofibrous La{sub 0.9}A{sub 0.1}MnO{sub 3} with macroscopic shapes was successfully obtained. CNFs template method used here is facile, effective and reproducible. The obtained materials show superior catalytic activity in soot combustion. The catalytic order is La{sub 0.9}Ag{sub 0.1}MnO{sub 3} > La{sub 0.9}Cu{sub 0.1}MnO{sub 3} > La{sub 0.9}Ca{sub 0.1}MnO{sub 3}. - Abstract: Fabrication of nanofibrous La{sub 0.9}A{sub 0.1}MnO{sub 3} (A = Ca, Cu, Ag) perovskite-type oxides with macroscopic shapes can be successfully obtained by using CNFs as templates. Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analysis confirmed the template effect and formation of nanofibrous perovskite-type oxides on macroscopic silica fiber. It turned out that it is reliable to control the desired single-phase La{sub 0.9}A{sub 0.1}MnO{sub 3} (A = Ca, Cu, Ag) perovskite-type oxides formation by tuning the corresponding metal ratio during preparation process. Furthermore, it showed that the as-prepared nanofibrous La{sub 0.9}A{sub 0.1}MnO{sub 3} (A = Ca, Cu, Ag) perovskite-type oxides can greatly decrease the combustion temperature of nanosized carbon black particles, and follows the order of La{sub 0.9}Ag{sub 0.1}MnO{sub 3} > La{sub 0.9}Cu{sub 0.1}MnO{sub 3} > La{sub 0.9}Ca{sub 0.1}MnO{sub 3}, indicating their high potential application prospects in diesel soot particles treatment.

  5. Magnetoresistance reversal in antiperovskite compound Mn{sub 3}Cu{sub 0.5}Zn{sub 0.5}N

    SciTech Connect (OSTI)

    Zhang, X. H.; Yin, Y.; Yuan, Q.; Han, J. C. [Center for Composite Materials, Harbin Institute of Technology, Harbin 150080 (China); Zhang, Z. H. [Liaoning Key Materials Laboratory for Railway, School of Materials Science and Engineering, Dalian Jiaotong University, Dalian 116028 (China); Jian, J. K. [School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Zhao, J. G., E-mail: zhaojinggeng@163.com, E-mail: songbo@hit.edu.cn; Song, B., E-mail: zhaojinggeng@163.com, E-mail: songbo@hit.edu.cn [Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080 (China)

    2014-03-28

    We report detailed investigations of the structure, magnetic properties, electronic transport, and specific heat in Mn-based antiperovskite compounds Mn{sub 3}Cu{sub 0.5}Zn{sub 0.5}N. Most strikingly, there are several fascinating features: (i) The magnetoresistance at 30?kOe (40?kOe) exceeds ?1% (?2%) over a temperature span of ?70?K (?25?K) from 5 to 140?K; (ii) magnetoresistance fluctuates at temperatures of 100200?K, including an obvious sign reversal from negative to positive at ?140?K. Analysis of the specific heat reveals that the magnetoresistance reversal may originate from the reconstruction of the Fermi surface accompanying an antiferromagnetic-ferromagnetic transition.

  6. Ab initio construction of magnetic phase diagrams in alloys: The case of Fe1-xMnxPt

    SciTech Connect (OSTI)

    Pujari, B. S.; Larson, P.; Antropov, V. P.; Belashchenko, K. D.

    2015-07-28

    A first-principles approach to the construction of concentration-temperature magnetic phase diagrams of metallic alloys is presented. The method employs self-consistent total energy calculations based on the coherent potential approximation for partially ordered and noncollinear magnetic states and is able to account for competing interactions and multiple magnetic phases. The application to the Fe1–xMnxPt “magnetic chameleon” system yields the sequence of magnetic phases at T = 0 and the c-T magnetic phase diagram in good agreement with experiment, and a new low-temperature phase is predicted at the Mn-rich end. The importance of non-Heisenberg interactions for the description of the magnetic phase diagram is demonstrated.

  7. Transverse thermoelectric effect in La{sub 0.67}Sr{sub 0.33}MnO{sub 3}|SrRuO{sub 3} superlattices

    SciTech Connect (OSTI)

    Shiomi, Y.; Handa, Y.; Kikkawa, T.; Saitoh, E.

    2015-06-08

    Transverse thermoelectric effects in response to an out-of-plane heat current have been studied in an external magnetic field for ferromagnetic superlattices consisting of La{sub 0.67}Sr{sub 0.33}MnO{sub 3} and SrRuO{sub 3} layers. The superlattices were fabricated on SrTiO{sub 3} substrates by pulsed laser deposition. We found that the sign of the transverse thermoelectric voltage for the superlattices is opposite to that for La{sub 0.67}Sr{sub 0.33}MnO{sub 3} and SrRuO{sub 3} single layers at 200?K, implying an important role of spin Seebeck effects inside the superlattices. At 10?K, the magnetothermoelectric curves shift from the zero field due to an antiferromagnetic coupling between layers in the superlattices.

  8. Strain-induced orbital polarization and multiple phase transitions in Ba{sub 2}MnWO{sub 6} from first principles

    SciTech Connect (OSTI)

    Ju, Weiwei; Zhao, Bao; Yang, Zhongqin

    2013-11-28

    Electronic structures of double perovskite Ba{sub 2}MnWO{sub 6} with epitaxial strain are explored by using methods based on density functional theory. An in-plane compressive strain is found not only resulting in a semiconductor-metal transition (SMT), but also altering the magnetic structures, from different kinds of antiferromagnetic to ferromagnetic orders. Orbital polarization and different orbital occupancies of Mn d{sub z{sup 2}} and d{sub x{sup 2}?y{sup 2}} states, induced by the epitaxial strain, are employed to understand the SMT. The rich magnetic phase transitions are rationalized by a magnetic stabilization mechanism. Our results show that many technological applications may be carried out in the material with the control of epitaxial strain.

  9. Abinitio construction of magnetic phase diagrams in alloys: The case of Fe1-xMnxPt

    SciTech Connect (OSTI)

    Pujari, B. S.; Larson, P.; Antropov, V. P.; Belashchenko, K. D.

    2015-07-28

    A first-principles approach to the construction of concentration-temperature magnetic phase diagrams of metallic alloys is presented. The method employs self-consistent total energy calculations based on the coherent potential approximation for partially ordered and noncollinear magnetic states and is able to account for competing interactions and multiple magnetic phases. The application to the Fe1xMnxPt magnetic chameleon system yields the sequence of magnetic phases at T = 0 and the c-T magnetic phase diagram in good agreement with experiment, and a new low-temperature phase is predicted at the Mn-rich end. The importance of non-Heisenberg interactions for the description of the magnetic phase diagram is demonstrated.

  10. Alternating magnetic anisotropy of Li2(Li1xTx)N (T = Mn, Fe, Co, and Ni)

    SciTech Connect (OSTI)

    Jesche, A.; Ke, L.; Jacobs, J. L.; Harmon, B.; Houk, R. S.; Canfield, P. C.

    2015-05-11

    Substantial amounts of the transition metals Mn, Fe, Co, and Ni can be substituted for Li in single crystalline Li2(Li1xTx)N. Isothermal and temperature-dependent magnetization measurements reveal local magnetic moments with magnitudes significantly exceeding the spin-only value. The additional contributions stem from unquenched orbital moments that lead to rare-earth-like behavior of the magnetic properties. Accordingly, extremely large magnetic anisotropies have been found. Most notably, the magnetic anisotropy alternates as easy plane?easy axis?easy plane?easy axis when progressing from T = Mn ? Fe ? Co ? Ni. This behavior can be understood based on a perturbation approach in an analytical, single-ion model. As a result, the calculated magnetic anisotropies show surprisingly good agreement with the experiment and capture the basic features observed for the different transition metals.

  11. Low-temperature grown quaternary Heusler-compound Co{sub 2}Mn{sub 1-x}Fe{sub x}Si films on Ge(111)

    SciTech Connect (OSTI)

    Yamada, S.; Murakami, T.; Hamaya, K.; Varaprasad, B.; Rajanikanth, A.; Hono, K.; Takahashi, Y. K.; Miyao, M.

    2011-04-01

    Highly ordered quaternary Co{sub 2}Mn{sub 1-x}Fe{sub x}Si films on Ge(111) are explored for spintronic device applications on Si-large-scale integrated circuit (LSI) platform. By using low-temperature molecular beam epitaxy techniques, relatively large magnetic moments are demonstrated for x between 0.50 and 1.0 despite extremely low temperature growth of 130 deg. C. Also, L2{sub 1}-ordered crystal structures can be realized even on a group-IV semiconductor substrate, Ge, compatible with Si-LSI technologies. By the point contact Andreev reflection method, the spin polarization of Co{sub 2}Mn{sub 0.5}Fe{sub 0.5}Si films is estimated to be P= 0.58 {+-} 0.02. We believe that this study will be a first step for integration of high-performance spintronic applications with next ultra LSI.

  12. One Dimensional(1D)-to-2D Crossover of Spin Correlations in the 3D Magnet ZnMn2O4

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Disseler, S. M.; Chen, Y.; Yeo, S.; Gasparovic, G.; Piccoli, P. M. B.; Schultz, A. J.; Qiu, Y.; Huang, Q.; Cheong, S. -W.; Ratcliff, W.

    2015-12-08

    In this paper we report on the intriguing evolution of the dynamical spin correlations of the frustrated spinel ZnMn2O4. Inelastic neutron scattering and magnetization studies reveal that the dynamical correlations at high temperatures are 1D. At lower temperature, these dynamical correlations become 2D. Surprisingly, the dynamical correlations condense into a quasi 2D Ising-like ordered state, making this a rare observation of two dimensional order on the spinel lattice. Remarkably, 3D ordering is not observed down to temperatures as low as 300 mK. This unprecedented dimensional crossover stems from frustrated exchange couplings due to the huge Jahn-Teller distortions around Mn3+ ionsmore » on the spinel lattice.« less

  13. Alternating magnetic anisotropy of Li2(Li1–xTx)N (T = Mn, Fe, Co, and Ni)

    SciTech Connect (OSTI)

    Jesche, A.; Ke, L.; Jacobs, J. L.; Harmon, B.; Houk, R. S.; Canfield, P. C.

    2015-05-11

    Substantial amounts of the transition metals Mn, Fe, Co, and Ni can be substituted for Li in single crystalline Li2(Li1–xTx)N. Isothermal and temperature-dependent magnetization measurements reveal local magnetic moments with magnitudes significantly exceeding the spin-only value. The additional contributions stem from unquenched orbital moments that lead to rare-earth-like behavior of the magnetic properties. Accordingly, extremely large magnetic anisotropies have been found. Most notably, the magnetic anisotropy alternates as easy plane→easy axis→easy plane→easy axis when progressing from T = Mn → Fe → Co → Ni. This behavior can be understood based on a perturbation approach in an analytical, single-ion model. As a result, the calculated magnetic anisotropies show surprisingly good agreement with the experiment and capture the basic features observed for the different transition metals.

  14. Combustion Synthesis of Nanoparticulate LiMgxMn1-xPO4 (x=0, 0.1, 0.2) Carbon Composites

    SciTech Connect (OSTI)

    Doeff, Marca M; Chen, Jiajun; Conry, Thomas E.; Wang, Ruigang; Wilcox, James; Aumentado, Albert

    2009-12-14

    A combustion synthesis technique was used to prepare nanoparticulate LiMgxMn1-xPO4 (x=0, 0.1,0.2)/carbon composites. Powders consisted of carbon-coated particles about 30 nm in diameter, which were partly agglomerated into larger secondary particles. The utilization of the active materials in lithium cells depended most strongly upon the post-treatment and the Mg content, and was not influenced by the amount of carbon. Best results were achieved with a hydrothermally treated LiMg0.2Mn0.8PO4/C composite, which exhibited close to 50percent utilization of the theoretical capacity at a C/2 discharge rate.

  15. MN Center for Renewable Energy: Cellulosic Ethanol, Optimization of Bio-fuels in Internal Combustion Engines, & Course Development for Technicians in These Areas

    SciTech Connect (OSTI)

    John Frey

    2009-02-22

    This final report for Grant #DE-FG02-06ER64241, MN Center for Renewable Energy, will address the shared institutional work done by Minnesota State University, Mankato and Minnesota West Community and Technical College during the time period of July 1, 2006 to December 30, 2008. There was a no-cost extension request approved for the purpose of finalizing some of the work. The grant objectives broadly stated were to 1) develop educational curriculum to train technicians in wind and ethanol renewable energy, 2) determine the value of cattails as a biomass crop for production of cellulosic ethanol, and 3) research in Optimization of Bio-Fuels in Internal Combustion Engines. The funding for the MN Center for Renewable Energy was spent on specific projects related to the work of the Center.

  16. Intrinsic quantum anomalous Hall effect in the kagome lattice Cs2LiMn3F12

    SciTech Connect (OSTI)

    Xu, Gang; Lian, Biao; Zhang, Shou -Cheng

    2015-10-27

    In a kagome lattice, the time reversal symmetry can be broken by a staggered magnetic flux emerging from ferromagnetic ordering and intrinsic spin-orbit coupling, leading to several well-separated nontrivial Chern bands and intrinsic quantum anomalous Hall effect. Based on this idea and ab initio calculations, we propose the realization of the intrinsic quantum anomalous Hall effect in the single layer Cs2Mn3F12 kagome lattice and on the (001) surface of a Cs2LiMn3F12 single crystal by modifying the carrier coverage on it, where the band gap is around 20 meV. Furthermore, a simplified tight binding model based on the in-plane ddσ antibonding states is constructed to understand the topological band structures of the system.

  17. (Ca,Na)(Zn,Mn){sub 2}As{sub 2}: A new spin and charge doping decoupled diluted ferromagnetic semiconductor

    SciTech Connect (OSTI)

    Zhao, K.; Chen, B. J.; Deng, Z.; Zhao, G. Q.; Zhu, J. L.; Liu, Q. Q.; Wang, X. C.; Han, W.; Frandsen, B.; Liu, L.; Cheung, S.; Uemura, Y. J.; Ning, F. L.; Munsie, T. J. S.; Medina, T.; Luke, G. M.; Carlo, J. P.; Munevar, J.; Zhang, G. M.; Jin, C. Q.

    2014-10-28

    Here, we report the successful synthesis of a spin- and charge-decoupled diluted magnetic semiconductor (DMS) (Ca,Na)(Zn,Mn){sub 2}As{sub 2}, crystallizing into the hexagonal CaAl{sub 2}Si{sub 2} structure. The compound shows a ferromagnetic transition with a Curie temperature up to 33?K with 10% Na doping, which gives rise to carrier density of n{sub p}???10{sup 20?}cm{sup ?3}. The new DMS is a soft magnetic material with H{sub C}?Mn doping, ferromagnetic order is accompanied by an interaction between the local spin and mobile charge, giving rise to a minimum in resistivity at low temperatures and localizing the conduction electrons. The system provides an ideal platform for studying the interaction of the local spins and conduction electrons.

  18. One Dimensional(1D)-to-2D Crossover of Spin Correlations in the 3D Magnet ZnMn2O4

    SciTech Connect (OSTI)

    Disseler, S. M.; Chen, Y.; Yeo, S.; Gasparovic, G.; Piccoli, P. M. B.; Schultz, A. J.; Qiu, Y.; Huang, Q.; Cheong, S. -W.; Ratcliff, W.

    2015-12-08

    In this paper we report on the intriguing evolution of the dynamical spin correlations of the frustrated spinel ZnMn2O4. Inelastic neutron scattering and magnetization studies reveal that the dynamical correlations at high temperatures are 1D. At lower temperature, these dynamical correlations become 2D. Surprisingly, the dynamical correlations condense into a quasi 2D Ising-like ordered state, making this a rare observation of two dimensional order on the spinel lattice. Remarkably, 3D ordering is not observed down to temperatures as low as 300 mK. This unprecedented dimensional crossover stems from frustrated exchange couplings due to the huge Jahn-Teller distortions around Mn3+ ions on the spinel lattice.

  19. Magnetic properties of Ni40+xMn39-xSn21 (x=0, 2, 4, 6 and 8 at.%) Heusler alloys

    SciTech Connect (OSTI)

    Lazpita, P.; Lograsso, T.; Schlagel, D. L.

    2014-01-27

    The low electron concentration region (e/a < 7.75) of the magnetic phase diagram of the off-stoichiometric NiMnSn Heusler alloys was investigated in detail by DSC and magnetization measurements of the Ni40+xMn39?xSn21(x = 0, 2, 4, 6 and 8 at.%) alloys. The alloys show a stable austenitic phase without any martensitic transformation down to 5 K even after heat treatment. The Curie temperature exhibits a broad maximum over a large composition range. The evolution of the magnetic moment with the electron concentration fits the data of previous studies and confirms the peak-like dependence in the extended range of e/a values predicted by ab initio calculations. The explored part of the moment versus e/a curve can be explained in terms of a localized magnetic moment model and full atomic order in the alloys.

  20. Perpendicular magnetic anisotropy of Mn{sub 4}N films on MgO(001) and SrTiO{sub 3}(001) substrates

    SciTech Connect (OSTI)

    Yasutomi, Yoko; Ito, Keita; Sanai, Tatsunori; Toko, Kaoru; Suemasu, Takashi

    2014-05-07

    We grew Mn{sub 4}N epitaxial thin films capped with Au layers on MgO(001) and SrTiO{sub 3}(001) substrates by molecular beam epitaxy. Perpendicular magnetic anisotropy (PMA) was confirmed in all the samples at room temperature from the magnetization versus magnetic field curves using superconducting quantum interference device magnetometer. From the ω-2θ x-ray diffraction (XRD) and ϕ-2θ{sub χ} XRD patterns, the ratios of perpendicular lattice constant c to in-plane lattice constant a, c/a, were found to be about 0.99 for all the samples. These results imply that PMA is attributed to the in-plane tensile strain in the Mn{sub 4}N films.

  1. Magnetic anisotropy induced by crystal distortion in Ge{sub 1−x}Mn{sub x}Te/PbTe//KCl (001) ferromagnetic semiconductor layers

    SciTech Connect (OSTI)

    Knoff, W. Łusakowski, A.; Domagała, J. Z.; Minikayev, R.; Taliashvili, B.; Łusakowska, E.; Pieniążek, A.; Szczerbakow, A.; Story, T.

    2015-09-21

    Ferromagnetic resonance (FMR) study of magnetic anisotropy is presented for thin layers of IV-VI diluted magnetic semiconductor Ge{sub 1−x}Mn{sub x}Te with x = 0.14 grown by molecular beam epitaxy on KCl (001) substrate with a thin PbTe buffer. Analysis of the angular dependence of the FMR resonant field reveals that an easy magnetization axis is located near to the normal to the layer plane and is controlled by two crystal distortions present in these rhombohedral Ge{sub 1−x}Mn{sub x}Te layers: the ferroelectric distortion with the relative shift of cation and anion sub-lattices along the [111] crystal direction and the biaxial in-plane, compressive strain due to thermal mismatch.

  2. Left-handed properties of manganite-perovskites La{sub 1-x}Sr{sub x}MnO{sub 3} at various dopant concentrations

    SciTech Connect (OSTI)

    Belozorov, D. P.; Girich, A. A.; Tarapov, S. I.; Pogorily, A. M.; Tovstolytkin, A. I.; Belous, A. G.; Solopan, S. A.

    2014-03-15

    The experimental study of Double Negative (DNG) state of electromagnetic wave propagating in lanthanum manganite-perovskites doped with strontium La{sub 1-x}Sr{sub x}MnO{sub 3} is provided firstly below individual Curie temperatures (in ferromagnetic metal state (FM) for La{sub 1-x}Sr{sub x}MnO{sub 3}). Various dopant concentrations are considered for ceramic specimens: x = 0.15;??0.225;??0.3;??0.45;??0.6. It is shown that dependence of the DNG-peak intensity on dopant concentration is sharply non-monotone with maximum at the dopant concentrations x = 0.225 0.3. This behaviour follows the change of Curie temperature with increase of dopant concentration in such substances. The obtained dependence of DNG peak intensity supports the opinion concerning the role of disorder in highly doped manganite-perovskite magnetic ceramics under study.

  3. FTIR and Raman Study of the LixTiyMn1-yO2 (y = 0, 0.11) Cathodes in Methylpropyl Pyrrolidinium Bis(fluoro-sulfonyl)imide, LiTFSI Electrolyte

    SciTech Connect (OSTI)

    Hardwick, L.J.; Lucas, I.T.; Doeff, M.M.; Kostecki, R.; Saint, J.A.

    2009-02-02

    This work demonstrates the protective effect of partial titanium substitution in Li{sub x}Ti{sub 0.11}Mn{sub 0.89}O{sub 2} against surface decomposition in room-temperature ionic liquid (RTILs) cells. Raman microscopy and reflectance Fourier transform IR (FTIR) spectroscopy were used to analyze electrodes recovered from cycled Li/Li{sub x}Ti{sub y}Mn{sub 1-y}O{sub 2} (y=0, 0.11) cells containing the 0.5 mol/kg LiTFSI in P{sub 13}FSI RTIL electrolyte. [TFSI=bis(trifluoromethanesulfonyl)imide.] Raman and FTIR spectra of cycled Li{sub x}MnO{sub 2} cathodes showed many distinct bands that can be attributed to both the electrolyte and electrode decomposition products. The thickness of the amorphous porous layer on the Li{sub x}MnO{sub 2} cathode increased during cycling. The surface degradation of Li{sub x}MnO{sub 2} and precipitation of electrolyte decomposition products contributed to the film growth. Improved cycling behavior was observed in cells containing Li{sub x}Ti{sub 0.11}Mn{sub 0.89}O{sub 2}, yet Raman spectroscopy also showed possible surface degradation. The FTIR spectra of cycled Li{sub x}MnO{sub 2} and Li{sub x}Ti{sub 0.11}Mn{sub 0.89}O{sub 2} cathodes displayed bands characteristic for LiSO{sub 3}CF{sub 3} and Li{sub 2}NSO{sub 2}CF{sub 3}, which originate from the reaction of the TFSI anion with traces of water present in the cell.

  4. Al{sub 70}Pd{sub 21.5}Mn{sub 8.5}: A quasicrystal showing the de haas-van Alphen effect

    SciTech Connect (OSTI)

    Haanappel, E.G.; Kycia, S.W.; Harmon, B.N.; Canfield, P.C.; Goldman, A.I.; Rabson, D.A.; Thompson, J.D.; Mueller, F.M.

    1995-07-01

    We have measured the de Haas-van Alphen effect in the icosahedral quasicrystal Al{sub 70}Pd{sub 21.5}Mn{sub 8.5}. We have found two well-defined frequencies with the magnetic field parallel to a five-fold axis, and two different ones with the field parallel to a two-fold axis. On increasing the temperature, the amplitude of the oscillations substantially decreased, suggesting that the carriers have large masses.

  5. Flower-like nanostructure MNb{sub 2}O{sub 6} (M = Mn, Zn) with high surface area: Hydrothermal synthesis and enhanced photocatalytic performance

    SciTech Connect (OSTI)

    Huang, Xue; Jing, Yan; Yang, Jia; Ju, Jing; Cong, Rihong; Gao, Wenliang; Yang, Tao

    2014-03-01

    Graphical abstract: - Highlights: • MNb{sub 2}O{sub 6} was prepared by a mild two-step hydrothermal method. • Their flower-like nanostructure morphology was studied by SEM and TEM. • High BET surface areas for MnNb{sub 2}O{sub 6} (∼50 m{sup 2}/g) and ZnNb{sub 2}O{sub 6} (∼100 m{sup 2}/g). • Band gap energies were estimated by UV–vis diffuse reflectance spectra. • Photocatalytic activities were evaluated under UV-light irradiation. - Abstract: Nano-scaled MNb{sub 2}O{sub 6} (M = Mn, Zn) was successfully synthesized via a two-step hydrothermal method. It is important to control the exact pH of the reaction solution in order to obtain pure products. The as-prepared samples both crystallize in the columbite structure. Interestingly, the products possess a flower-like morphology in a pseudo-six-fold symmetry, which is in fact arrayed by two-dimensional nanosheets. Their surface areas (51 m{sup 2}/g for MnNb{sub 2}O{sub 6} and 103 m{sup 2}/g for ZnNb{sub 2}O{sub 6}) are about 25–50 times of those prepared by solid state reaction. UV–vis diffuse reflectance spectra show the nano-scaled sample has a stronger absorption and a narrower band gap than its bulk form. The estimated band gap energies are 2.70 eV (MnNb{sub 2}O{sub 6}) and 3.77 eV (ZnNb{sub 2}O{sub 6}), respectively. The nano-scaled ZnNb{sub 2}O{sub 6} exhibits a double enhancement of photocatalytic activity in the decolorization of methylene blue than bulk ZnNb{sub 2}O{sub 6}.

  6. Non-aqueous solution preparation of doped and undoped Li{sub x}Mn{sub y}O{sub z}

    DOE Patents [OSTI]

    Boyle, T.J.; Voigt, J.A.

    1997-05-20

    A method is described for generation of phase-pure doped and undoped Li{sub x}Mn{sub y}O{sub z} precursors. The method of this invention uses organic solutions instead of aqueous solutions or nonsolution ball milling of dry powders to produce phase-pure precursors. These precursors can be used as cathodes for lithium-polymer electrolyte batteries. Dopants may be homogeneously incorporated to alter the characteristics of the powder. 1 fig.

  7. Colossal thermoelectric power in charge ordered lanthanum calcium manganites (La{sub 0.5}Ca{sub 0.5}MnO{sub 3})

    SciTech Connect (OSTI)

    Joy, Lija K.; Anantharaman, M. R.; Shanmukharao Samatham, S.; Ganesan, V.; Thomas, Senoy; Al-Harthi, Salim; Liebig, A.; Albrecht, M.

    2014-12-07

    Lanthanum calcium manganites (La{sub 0.5}Ca{sub 0.5}MnO{sub 3}) with a composition close to charge ordering, synthesized by high energy ball milling, was found to exhibit colossal thermoelectric power. Thermoelectric power (TEP) data was systematically analyzed by dividing the entire temperature range (5 K–300 K) into three different regimes to explore different scattering mechanisms involved. Mandal's model has been applied to explain TEP data in the region below the Curie temperature (T{sub C}). It has been found that the variation of thermoelectric power with temperature is pronounced when the system enters the charge ordered region at T < 200 K. For temperatures lower than 120 K, due to the co-existence of charge ordered state with a spin-glass state, the variation of thermoelectric power is maximum and exhibited a peak value of −80 mV/K at 58 K. This has been explained by incorporating Kondo properties of the spin-glass along with magnon scattering. FC-ZFC magnetization measurements indicate the existence of a glassy state in the region corresponding to a maximum value of thermoelectric power. Phonon drag contribution instead of spin-glass contribution is taken into account to explain TEP in the region 120 K < T < T{sub C}. Mott's polaronic contribution of charge carriers are considered to interpret TEP in the high temperature region (T > T{sub C}). The optimal Mn{sup 4+}-Mn{sup 3+} concentration in charge ordered La{sub 0.5}Ca{sub 0.5}MnO{sub 3} was examined by X-ray Photoelectron Spectroscopy analysis which confirms the charge ordered nature of this compound.

  8. Synthesis, crystal structure and properties of [(dien){sub 2}Mn]Ge{sub 2}S{sub 4} with mixed-valent Ge centers

    SciTech Connect (OSTI)

    Yue, Cheng-Yang; Yuan, Zhuang-Dong; Zhang, Lu-Ge; Wang, Ya-Bai; Liu, Guo-Dong; Gong, Liao-Kuo; Lei, Xiao-Wu

    2013-10-15

    One new manganese thiogermanate, [(dien){sub 2}Mn]Ge{sub 2}S{sub 4} (dien=diethylenetriamine), was prepared under mild solvothermal conditions and structurally and spectroscopically characterized. The title compound crystallizes in the orthorhombic system, chiral space group P2{sub 1}2{sub 1}2{sub 1} (no. 19) with a=9.113(4) Å, b=12.475(5) Å, c=17.077(7) Å, V=1941.5(15) Å{sup 3} and Z=4. Its structure features a three-dimensional (3D) network composed of a one-dimensional (1D) [Ge{sub 2}S{sub 4}]{sup 2−} anionic chain and a [(dien){sub 2}Mn]{sup 2+} complex interconnected via various hydrogen bonds. The most interesting structural feature of the compound is the presence of two different oxidation states of germanium centers in the 1D [Ge{sub 2}S{sub 4}]{sup 2−} chain, which is also supported by the result of X-ray photoelectron spectroscopy measurement. The optical property of the title compound has also been studied by UV–vis spectra. - Graphical abstract: One new thiogermanate, [(dien){sub 2}Mn]Ge{sub 2}S{sub 4}, contains a one-dimensional [Ge{sub 2}S{sub 4}]{sup 2−} anionic chain with two different oxidation states of germanium centers. Display Omitted - Highlights: • One new manganese thiogermanate [(dien){sub 2}Mn]Ge{sub 2}S{sub 4} was prepared. • The compound features 1D [Ge{sub 2}S{sub 4}]{sup 2−} chain composed of [Ge{sup II}S{sub 4}] and [Ge{sup IV}S{sub 4}] tetrahedra. • The first example of inorganic–organic hybrid thiogermanates with mixed valent Ge centers.

  9. First-Principles Calculations, Electrochemical and X-ray Absorption Studies of Li-Ni-PO4 Surface-Treated xLi2MnO3 (1 x)LiMO2 (M = Mn, Ni, Co) Electrodes for Li-Ion Batteries

    SciTech Connect (OSTI)

    Wolverton, Christopher; Croy, J R; Balasubramanian, M; Kang, Sun-Ho; Lopez-Rivera, C. M.; Thackeray, Michael M.

    2012-01-01

    It has been previously hypothesized that the enhanced rate capability of Li-Ni-PO{sub 4}-treated xLi{sub 2}MnO{sub 3} {center_dot} (1-x)LiMO{sub 2} positive electrodes (M = Mn, Ni, Co) in Li-ion batteries might be associated with a defect Ni-doped Li{sub 3}PO{sub 4} surface structure [i.e., Li{sub 3-2y}Ni{sub y}PO{sub 4} (0 < y < 1)], thereby promoting fast Li{sup +}-ion conduction at the xLi{sub 2}MnO{sub 3} {center_dot} (1-x)LiMO{sub 2} particle surface. In this paper, the solubility of divalent metals (Fe, Mn, Ni, Mg) in {gamma}-Li{sub 3}PO{sub 4} is predicted with the first-principles GGA+U method in an effort to understand the enhanced rate capability. The predicted solubility (x) is extremely small; this finding is consistent with experimental evidence: 1) X-ray diffraction data obtained from Li-Ni-PO{sub 4}-treated xLi{sub 2}MnO{sub 3} {center_dot} (1-x)LiMO{sub 2} electrodes that show that, after annealing at 550 C, a Li{sub 3}PO{sub 4}-like structure forms as a second phase at the electrode particle surface, and 2) X-ray absorption spectroscopy, which indicate that the nickel ions are accommodated in the transition metal layers of the Li{sub 2}MnO{sub 3} component during the annealing process. However, electrochemical studies of Li{sub 3-2y}Ni{sub y}PO{sub 4}-treated xLi{sub 2}MnO{sub 3} {center_dot} (1-x)LiMO{sub 2} electrodes indicate that their rate capability increases as a function of y over the range y = 0 (Li{sub 3}PO{sub 4}) to y = 1 (LiNiPO{sub 4}), strongly suggesting that, at some level, the nickel ions play a role in reducing electrochemical impedance and increasing electrode stability at the electrode particle surface.

  10. Electronic structure, magnetism, and antisite disorder in CoFeCrGe and CoMnCrAl quaternary Heusler alloys

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Enamullah, .; Venkateswara, Y.; Gupta, Sachin; Varma, Manoj Raama; Singh, Prashant; Suresh, K. G.; Alam, Aftab

    2015-12-10

    In this study, we present a combined theoretical and experimental study of two quaternary Heusler alloys CoFeCrGe (CFCG) and CoMnCrAl (CMCA), promising candidates for spintronics applications. Magnetization measurement shows the saturation magnetization and transition temperature to be 3 μB, 866 K and 0.9 μB, 358 K for CFCG and CMCA respectively. The magnetization values agree fairly well with our theoretical results and also obey the Slater-Pauling rule, a prerequisite for half metallicity. A striking difference between the two systems is their structure; CFCG crystallizes in fully ordered Y-type structure while CMCA has L21 disordered structure. The antisite disorder adds amore » somewhat unique property to the second compound, which arises due to the probabilistic mutual exchange of Al positions with Cr/Mn and such an effect is possibly expected due to comparable electronegativities of Al and Cr/Mn. Ab initio simulation predicted a unique transition from half metallic ferromagnet to metallic antiferromagnet beyond a critical excess concentration of Al in the alloy.« less

  11. Magnetoelectric coupling tuned by competing single iron anisotropies in Mn1-xNixTiO3

    SciTech Connect (OSTI)

    Chi, Songxue; Ye, Feng; Zhou, Haidong D.; Choi, E. S.; Hwang, J.; Cao, Huibo; Fernandez-Baca, Jaime A.

    2014-01-01

    A flop of electric polarization from Pc to Pa is observed in MnTiO3 as a spin flop transtion is triggered by a c-axis magnetic field, Hc=7 T. The critical magnetic field for Pa is significantly reduced in Mn1-xNixTiO3 (x=0.33). Neutron diffraction measurements revealed similar magnetic arrangements for the two compositions where the ordered spins couple antiferromagnetically with their nearest intra- and inter-planar neighbors. In the x=0.33 system, the single ion anisotropies of Mn2+ and Ni2+ compete and give rise to an additional spin reorientation transition at TR. A magnetic field, Hc, aligns the spins along c for TRN. The rotation of the collinear spins away from the c-axis for TR alters the magnetic point symmetry and gives rise to new ME susceptibility tensor form. Such linear ME response provides satisfactory explanation for behavior of field-induced electric polarization in both compositions. As the Ni content increases to x=0.5 and 0.68, the ME effect disappears as a new magnetic phase emerges.

  12. Atomic-Resolution Visualization of Distinctive Chemical Mixing Behavior of Ni, Co and Mn with Li in Layered Lithium Transition-Metal Oxide Cathode Materials

    SciTech Connect (OSTI)

    Yan, Pengfei; Zheng, Jianming; Lv, Dongping; Wei, Yi; Zheng, Jiaxin; Wang, Zhiguo; Kuppan, Saravanan; Yu, Jianguo; Luo, Langli; Edwards, Danny J.; Olszta, Matthew J.; Amine, Khalil; Liu, Jun; Xiao, Jie; Pan, Feng; Chen, Guoying; Zhang, Jiguang; Wang, Chong M.

    2015-07-06

    Capacity and voltage fading of layer structured cathode based on lithium transition metal oxide is closely related to the lattice position and migration behavior of the transition metal ions. However, it is scarcely clear about the behavior of each of these transition metal ions. We report direct atomic resolution visualization of interatomic layer mixing of transition metal (Ni, Co, Mn) and lithium ions in layer structured oxide cathodes for lithium ion batteries. Using chemical imaging with aberration corrected scanning transmission electron microscope (STEM) and DFT calculations, we discovered that in the layered cathodes, Mn and Co tend to reside almost exclusively at the lattice site of transition metal (TM) layer in the structure or little interlayer mixing with Li. In contrast, Ni shows high degree of interlayer mixing with Li. The fraction of Ni ions reside in the Li layer followed a near linear dependence on total Ni concentration before reaching saturation. The observed distinctively different behavior of Ni with respect to Co and Mn provides new insights on both capacity and voltage fade in this class of cathode materials based on lithium and TM oxides, therefore providing scientific basis for selective tailoring of oxide cathode materials for enhanced performance.

  13. Effect of Zn doping on the magneto-caloric effect and critical constants of Mott insulator MnV{sub 2}O{sub 4}

    SciTech Connect (OSTI)

    Shahi, Prashant; Kumar, A.; Shukla, K. K.; Chatterjee, Sandip; Singh, Harishchandra; Ghosh, A. K.; Yadav, A. K.; Nigam, A. K.

    2014-09-15

    X-ray absorption near edge spectra (XANES) and magnetization of Zn doped MnV{sub 2}O{sub 4} have been measured and from the magnetic measurement the critical exponents and magnetocaloric effect have been estimated. The XANES study indicates that Zn doping does not change the valence states in Mn and V. It has been shown that the obtained values of critical exponents ?, ? and ? do not belong to universal class and the values are in between the 3D Heisenberg model and the mean field interaction model. The magnetization data follow the scaling equation and collapse into two branches indicating that the calculated critical exponents and critical temperature are unambiguous and intrinsic to the system. All the samples show large magneto-caloric effect. The second peak in magneto-caloric curve of Mn{sub 0.95}Zn{sub 0.05}V{sub 2}O{sub 4} is due to the strong coupling between orbital and spin degrees of freedom. But 10% Zn doping reduces the residual spins on the V-V pairs resulting the decrease of coupling between orbital and spin degrees of freedom.

  14. Large entropy change accompanying two successive magnetic phase transitions in TbMn{sub 2}Si{sub 2} for magnetic refrigeration

    SciTech Connect (OSTI)

    Li, Guoxing; Cheng, Zhenxiang E-mail: cheng@uow.edu.au; Fang, Chunsheng; Dou, Shixue; Wang, Jianli E-mail: cheng@uow.edu.au; Ren, Qingyong

    2015-05-04

    Structural and magnetic properties in TbMn{sub 2}Si{sub 2} are studied by variable temperature X-ray diffraction, magnetization, electrical resistivity, and heat capacity measurements. TbMn{sub 2}Si{sub 2} undergoes two successive magnetic transitions at around T{sub c1} = 50 K and T{sub c2} = 64 K. T{sub c1} remains almost constant with increasing magnetic field, but T{sub c2} shifts significantly to higher temperature. Thus, there are two partially overlapping peaks in the temperature dependence of magnetic entropy change, i.e., −ΔS{sub M} (T). The different responses of T{sub c1} and T{sub c2} to external magnetic field, and the overlapping of −ΔS{sub M} (T) around T{sub c1} and T{sub c2} induce a large refrigerant capacity (RC) within a large temperature range. The large reversible magnetocaloric effect (−ΔS{sub M}{sup peak} ∼ 16 J/kg K for a field change of 0–5 T) and RC (=396 J/kg) indicate that TbMn{sub 2}Si{sub 2} could be a promising candidate for low temperature magnetic refrigeration.

  15. Effect of niobium addition on the martensitic transformation and magnetocaloric effect in low hysteresis NiCoMnSn magnetic shape memory alloys

    SciTech Connect (OSTI)

    Emre, Baris; Bruno, Nickolaus M.; Yuce Emre, Suheyla; Karaman, Ibrahim

    2014-12-08

    The effect of Nb substitution for Ni in Ni{sub 45}Co{sub 5}Mn{sub 40}Sn{sub 10} magnetic shape memory alloys on their magnetic properties, martensitic transformation characteristics, transformation hysteresis, and magnetocaloric properties was studied using wavelength-dispersive X-ray spectroscopy, differential scanning calorimetry, and the temperature and field dependence of the magnetization. Ni{sub 45}Co{sub 5}Mn{sub 40}Sn{sub 10} alloy has a very low transformation hysteresis; however, the martensitic transformation temperatures are notably above room temperature, which is not desirable for magnetic refrigeration applications. In this study, small quantities of Nb substitution were shown to drastically shift the transformation temperatures to lower temperatures, at a rate of 68 K/at. % Nb, which is needed for household refrigeration. The austenite Curie temperature also decreased with increasing Nb content. However, a decrease in the latent heat of the martensitic transition was observed, which negatively affects the magnetic field-induced adiabatic temperature change capability. Still, the relatively large transformation entropy and the low transformation hysteresis make the Nb-doped Ni{sub 45}Co{sub 5}Mn{sub 40}Sn{sub 10} alloys potential candidates for solid state refrigeration near room temperature.

  16. Oxygen incorporation effects in annealed epitaxial La{sub (1-x)}Sr{sub x}MnO{sub 3} thin films

    SciTech Connect (OSTI)

    Petrisor, T.; Gabor, M. S.; Tiusan, C.; Boulle, A.; Bellouard, C.; Pana, O.; Petrisor, T.

    2011-06-15

    This paper presents our results regarding oxygen incorporation effects in epitaxial La{sub (1-x)}Sr{sub x}MnO{sub 3} thin films, deposited on SrTiO{sub 3} (001) single crystal substrates, by annealing in different gas mixtures of argon and oxygen. A particular emphasis is placed on the correlation of structural properties with the magnetic properties of the films, Curie temperature, and coercive field. In this sense, we demonstrate that the evolution of the diffuse part of the {omega}-scans performed on the films are due to oxygen excess in the film lattice, which creates cationic vacancies within the films. Also, we show that two regimes of oxygen incorporation in the films exist, one in which the films evolve toward a single phase and oxygen stoichiometry is recovered, and a second one dominated by oxygen over-doping effects. In order to support our study, XPS measurements were performed, from which we have evaluated the Mn{sup 3+}/Mn{sup 4+} ionic ratio.

  17. Martensitic transformation and phase stability of In-doped Ni-Mn-Sn shape memory alloys from first-principles calculations

    SciTech Connect (OSTI)

    Xiao, H. B.; Yang, C. P. Wang, R. L.; Luo, X.; Marchenkov, V. V.

    2014-05-28

    The effect of the alloying element Indium (In) on the martensitic transition, magnetic properties, and phase stabilities of Ni{sub 8}Mn{sub 6}Sn{sub 2?x}In{sub x} shape memory alloys has been investigated using the first-principles pseudopotential plane-wave method based on density functional theory. The energy difference between the austenitic and martensitic phases was found to increase with increasing In content, which implies an enhancement of the martensitic phase transition temperature (T{sub M}). Moreover, the formation energy results indicate that In-doping increases the relative stability of Ni{sub 8}Mn{sub 6}Sn{sub 2?x}In{sub x} both in austenite and martensite. This results from a reduction in density of states near the Fermi level regions caused by Ni-3dIn-5p hybridization when Sn is replaced by In. The equilibrium equation of state results show that the alloys Ni{sub 8}Mn{sub 6}Sn{sub 2?x}In{sub x} exhibit an energetically degenerated effect for an In content of x?=??1.5. This implies the coexistence of antiparallel and parallel configurations in the austenite.

  18. A thermo-mechanical correlation with driving forces for hcp martensite and twin formations in the FeMnC system exhibiting multicomposition sets

    SciTech Connect (OSTI)

    Nakano, Jinichiro

    2013-03-15

    Thermodynamic properties of the Fe-Mn-C system were investigated by using an analytical model constructed by a CALPHAD approach. Stacking fault energy (SFE) of the fcc structure with respect to the hcp phase was always constant at T0, independent of composition and temperature when the other related parameters were assumed to be constant. Experimental limits for the thermal hcp formation and the mechanical (deformation-induced) hcp formation were separated by the SFE at T0. The driving force for the fcc to hcp transition, defined as a dimensionless value dGm/(RT), was determined in the presence of Fe-rich and Mn-rich composition sets in each phase. Carbon tended to partition to the Mn-rich phase rather than to the Fe-rich phase for the studied compositions. The obtained results revealed a thermo-mechanical correlation with empirical yield strength, maximum true stress and maximum true strain. The proportionality between thermodynamics and mechanical properties is discussed.

  19. Room temperature ferrimagnetism and ferroelectricity in strained, thin films of BiFe 0.5 Mn 0.5 O 3

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Choi, Eun -Mi; Fix, Thomas; Kursumovic, Ahmed; Kinane, Christy J.; Arena, Darío; Sahonta, Suman -Lata; Bi, Zhenxing; Xiong, Jie; Yan, Li; Lee, Jun -Sik; et al

    2014-10-14

    Highly strained films of BiFe0.5Mn0.5O₃ (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetisation measurements demonstrated ferrimagnetism (TC ~ 600K), with a room temperature saturation moment (MS) of up to 90 emu/cc (~ 0.58 μB/f.u) on high quality (001) SrTiO₃. X-ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe³⁺ and Mn³⁺. While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magnetic properties were found to be strongly dependent on the strain statemore » in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above.« less

  20. Room temperature ferrimagnetism and ferroelectricity in strained, thin films of BiFe 0.5 Mn 0.5 O 3

    SciTech Connect (OSTI)

    Choi, Eun -Mi; Fix, Thomas; Kursumovic, Ahmed; Kinane, Christy J.; Arena, Darío; Sahonta, Suman -Lata; Bi, Zhenxing; Xiong, Jie; Yan, Li; Lee, Jun -Sik; Wang, Haiyan; Langridge, Sean; Kim, Young -Min; Borisevich, Albina Y.; MacLaren, Ian; Ramasse, Quentin M.; Blamire, Mark G.; Jia, Quanxi; MacManus-Driscoll, Judith L.

    2014-10-14

    Highly strained films of BiFe0.5Mn0.5O₃ (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetisation measurements demonstrated ferrimagnetism (TC ~ 600K), with a room temperature saturation moment (MS) of up to 90 emu/cc (~ 0.58 μB/f.u) on high quality (001) SrTiO₃. X-ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe³⁺ and Mn³⁺. While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magnetic properties were found to be strongly dependent on the strain state in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above.