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1

Complex magnetic behavior and high spin polarization in Fe3-xMnxSi alloys  

Science Journals Connector (OSTI)

Fe3Si is a ferromagnetic material with possible applications in magnetic tunnel junctions. When doped with Mn, the material shows a complex magnetic behavior, as suggested by older experiments. We employed the Korringa-Kohn-Rostoker Green-function method within density-functional theory in order to study the alloy Fe3-xMnxSi, with 0?x?1. Chemical disorder is described within the coherent potential approximation. In agreement with experiment, we find that the Mn atoms align ferromagnetically to the Fe atoms, and that the magnetization and Curie temperature drop with increasing Mn concentration x. The calculated spin polarization P at the Fermi level varies strongly with x, from P=-0.3 at x=0 (ordered Fe3Si) through P=0 at x=0.28, to P=+1 for x>0.75; i.e., at high Mn concentrations the system is half metallic. We discuss the origin of the trends of magnetic moments, exchange interactions, Curie temperature, and the spin polarization.

Marjana Ležai?, Phivos Mavropoulos, Stefan Blügel, and Hubert Ebert

2011-03-30T23:59:59.000Z

2

Mesoscopic Spin Magnetism  

Science Journals Connector (OSTI)

We investigate the spin magnetism of mesoscopic metallic grains. In the average response of an ensemble of grains there are corrections to macroscopic behavior due to both spectral fluctuations and electron-electron interactions. These corrections are a nonlinear function of the magnetic field. Their temperature dependence is calculated numerically and analytically. An experiment is proposed to measure the unknown interaction coupling constant in the Cooper channel. For a single sample the magnetization is found to fluctuate reproducibly about the mean. These fluctuations directly probe the energy level statistics.

H. Mathur; M. Gökçeda?; A. Douglas Stone

1995-03-06T23:59:59.000Z

3

Spin and orbital magnetization loops obtained using magnetic Compton scattering  

SciTech Connect (OSTI)

We present an application of magnetic Compton scattering (MCS) to decompose a total magnetization loop into spin and orbital magnetization contributions. A spin magnetization loop of SmAl{sub 2} was measured by recording the intensity of magnetic Compton scattering as a function of applied magnetic field. Comparing the spin magnetization loop with the total magnetization one measured by a vibrating sample magnetometer, the orbital magnetization loop was obtained. The data display an anti-coupled behavior between the spin and orbital magnetizations and confirm that the orbital part dominates the magnetization.

Itou, M.; Sakurai, Y. [Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198 (Japan)] [Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198 (Japan); Koizumi, A. [Graduate School of Materials Science, University of Hyogo, Hyogo 678-1297 (Japan)] [Graduate School of Materials Science, University of Hyogo, Hyogo 678-1297 (Japan)

2013-02-25T23:59:59.000Z

4

Quantum spins mimic refrigerator magnets - Argonne National Laboratories,  

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

Highlights > Quantum spins mimic refrigerator Highlights > Quantum spins mimic refrigerator magnets Quantum spins mimic refrigerator magnets By Joseph Bernstein * October 11, 2012 The behavior of magnetic moments in metal oxides such as layered iridium is dominated by strong spin-orbit coupling effects. In layered compounds such as Sr3Ir2O7 (shown on the left), the direction of these moments (blue arrows) is controlled at the quantum level by dipolar interactions that are akin to those of classical bar magnets. Another outcome is an unprecedented 'magnon gap' (shown at right), which was measured at the Argonne Advanced Photon Source and reveals that these underlying dipolar magnetic interactions are extremely strong. Current electronic devices depend on manipulating charge. Alternative approaches may rely on not only charge but also the spin of electrons.

5

Effects of coexisting spin disorder and antiferromagnetism on the magnetic behavior of nanostructured (Fe{sub 79}Mn{sub 21}){sub 1?x}Cu{sub x} alloys  

SciTech Connect (OSTI)

We report a magnetic study on nanostructured (Fe{sub 79}Mn{sub 21}){sub 1?x}Cu{sub x} (0.00???x???0.30) alloys using static magnetic measurements. The alloys are mainly composed by an antiferromagnetic fcc phase and a disordered region that displays a spin-glass-like behavior. The interplay between the antiferromagnetic and magnetically disordered phases establishes an exchange anisotropy that gives rise to a loop shift at temperatures below the freezing temperature of moments belonging to the disordered region. The loop shift is more noticeable as the Cu content increases, which also enhances the spin-glass-like features. Further, in the x?=?0.30 alloy the alignment imposed by applied magnetic fields higher than 4 kOe prevail over the configuration determined by the frustration mechanism that characterizes the spin glass-like phase.

Mizrahi, M., E-mail: mizrahi@fisica.unlp.edu.ar, E-mail: cabrera@fisica.unlp.edu.ar [INIFTA-CCT- La Plata-CONICET and Departamento de Física, Facultad de Ciencias Exactas, C. C. 67, Universidad Nacional de La Plata, 1900 La Plata (Argentina); Cabrera, A. F., E-mail: mizrahi@fisica.unlp.edu.ar, E-mail: cabrera@fisica.unlp.edu.ar; Desimoni, J. [IFLP-CCT-La Plata-CONICET and Departamento de Física, Facultad de Ciencias Exactas C.C. 67, Universidad Nacional de La Plata, 1900 La Plata (Argentina); Stewart, S. J. [IFLP-CCT-La Plata-CONICET and Departamento de Física, Facultad de Ciencias Exactas C.C. 67, Universidad Nacional de La Plata, 1900 La Plata (Argentina); Instituto Ciencias de la Salud, Universidad Nacional Arturo Jauretche, Av. Calchaquí No. 6200, Florencio Varela (Argentina)

2014-06-07T23:59:59.000Z

6

Spin glass behavior in FeAl2  

E-Print Network [OSTI]

Magnetic and transport measurements indicate FeAl2 to be an ordered intermetallic spin glass, with canonical behavior including a susceptibility cusp at T-f = 35 K and frequency-dependent susceptibility below T-f. The field-cooled and zero...

Lue, CS; Oner, Y.; Naugle, Donald G.; Ross, JH.

2001-01-01T23:59:59.000Z

7

Spin diffusion at finite electric and magnetic fields  

Science Journals Connector (OSTI)

Spin-transport properties at finite electric and magnetic fields are studied by using the generalized semiclassical Boltzmann equation. It is found that the spin-diffusion equation for nonequilibrium spin density and spin currents involves a number of length scales that explicitly depend on the electric and magnetic fields. The set of macroscopic equations can be used to address a broad range of the spin-transport problems in magnetic multilayers as well as in semiconductor heterostructure. A specific example of spin injection into semiconductors at arbitrary electric and magnetic fields is illustrated.

Y. Qi and S. Zhang

2003-02-27T23:59:59.000Z

8

Spin precession modulation in a magnetic bilayer  

SciTech Connect (OSTI)

We report on modulation of the spin precession in a Co/garnet bilayer by femtosecond laser excitation using time-resolved magneto-optical tools. Damped oscillations in the Faraday rotation transients representing precessional motion of the magnetization vector are observed in both the 2 nm Co layer and 1.8 {mu}m garnet of the bilayer with distinct frequencies differing by about a factor of two. The excitation efficiency of these precessions strongly depends on the out-of-plane magnetic field. The modulation effect with the coupling in a magnetic bilayer can be useful for non-thermally controlling the magnetization of nanomagnets and ultrafast switching in magnetic nanodevices.

Stupakiewicz, A.; Maziewski, A. [Laboratory of Magnetism, Faculty of Physics, University of Bialystok, Lipowa 41, Bialystok (Poland); Pashkevich, M. [Laboratory of Magnetism, Faculty of Physics, University of Bialystok, Lipowa 41, Bialystok (Poland); Scientific-Practical Materials Research Centre of the NASB, P. Brovki 19, Minsk (Belarus); Stognij, A.; Novitskii, N. [Scientific-Practical Materials Research Centre of the NASB, P. Brovki 19, Minsk (Belarus)

2012-12-24T23:59:59.000Z

9

Magnetic hysteresis in two model spin systems  

Science Journals Connector (OSTI)

A systematic study of hysteresis in model continuum and lattice spin systems is undertaken by constructing a statistical-mechanical theory wherein spatial fluctuations of the order parameter are incorporated. The theory is used to study the shapes and areas of the hysteresis loops as functions of the amplitude (H0) and frequency (?) of the magnetic field. The response of the spin systems to a pulsed magnetic field is also studied. The continuum model that we study is a three-dimensional (?2)2 model with O(N) symmetry in the large-N limit. The dynamics of this model are specified by a Langevin equation. We find that the area A of the hysteresis loop scales as A?H00.66?0.33 for low values of the amplitude and frequency of the magnetic field. The hysteretic response of a two-dimensional, nearest-neighbor, ferromagnetic Ising model is studied by a Monte Carlo simulation on 10×10, 20×20, and 50×50 lattices. The framework that we develop is compared with other theories of hysteresis. The relevance of these results to hysteresis in real magnets is discussed.

Madan Rao; H. R. Krishnamurthy; Rahul Pandit

1990-07-01T23:59:59.000Z

10

Electron spin magnetism of zigzag graphene nanoribbon edge states  

SciTech Connect (OSTI)

The electron spin states of zigzag graphene nanoribbon (ZGNR) edge play a pivotal role in the applications of graphene nanoribbons. However, the exact arrangements of the electron spins remain unclear to date. In this report, the electronic spin states of the ZGNR edge have been elucidated through a combination of quantum chemical investigation and previous electron spin resonance experiment observations. An alternating ? and ? spin configuration of the unpaired electrons along the ZGNR edge is established in ambient condition without any external magnetic field, and the origin of the spin magnetism of the ZGNR edge is revealed. It paves a pathway for the understanding and design of graphene based electronic and spintronic devices.

Xu, Kun, E-mail: xu83@purdue.edu; Ye, Peide D. [School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States)

2014-04-21T23:59:59.000Z

11

Spin microscope based on optically detected magnetic resonance  

DOE Patents [OSTI]

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2007-12-11T23:59:59.000Z

12

Spin microscope based on optically detected magnetic resonance  

DOE Patents [OSTI]

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2010-06-29T23:59:59.000Z

13

Spin microscope based on optically detected magnetic resonance  

DOE Patents [OSTI]

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of impaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2009-11-10T23:59:59.000Z

14

Spin microscope based on optically detected magnetic resonance  

DOE Patents [OSTI]

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2009-10-27T23:59:59.000Z

15

Localized whistlers in magnetized spin quantum plasmas  

SciTech Connect (OSTI)

The nonlinear propagation of electromagnetic (EM) electron-cyclotron waves (whistlers) along an external magnetic field, and their modulation by electrostatic small but finite amplitude ion-acoustic density perturbations are investigated in a uniform quantum plasma with intrinsic spin of electrons. The effects of the quantum force associated with the Bohm potential and the combined effects of the classical as well as the spin-induced ponderomotive forces (CPF and SPF, respectively) are taken into consideration. The latter modify the local plasma density in a self-consistent manner. The coupled modes of wave propagation is shown to be governed by a modified set of nonlinear Schroedinger-Boussinesq-like equations which admit exact solutions in form of stationary localized envelopes. Numerical simulation reveals the existence of large-scale density fluctuations that are self-consistently created by the localized whistlers in a strongly magnetized high density plasma. The conditions for the modulational instability (MI) and the value of its growth rate are obtained. Possible applications of our results, e.g., in strongly magnetized dense plasmas and in the next generation laser-solid density plasma interaction experiments are discussed.

Misra, A. P.; Brodin, G.; Marklund, M. [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden); Shukla, P. K. [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden); RUB International Chair, International Centre for Advanced Studies in Physical Sciences, Faculty of Physics and Astronomy, Ruhr University Bochum, D-44780 Bochum (Germany)

2010-11-15T23:59:59.000Z

16

Spin Correlations in a Magnetic Electron Gas  

Science Journals Connector (OSTI)

The density response function (???), the longitudinal spin-correlation function (?zz), the transverse spin-correlation function (?-+), and the cross-correlation function (??z) involving the density and the z component of spin density are computed by employing two generalized moment-conserving (MC) schemes for a magnetic electron gas. The two schemes differ in their treatment of the one-electron states. These functions are also computed in the random-phase approximation (RPA) including exchange processes, in two different ways, by solving the resulting integral equations by a variational method due to one of the authors. We prove that in the absence of spin-orbit interactions, ??z(q?,?)=?z?(q?,?), which enables us to set up a consistent MC scheme. In the paramagnetic state, only ??? and ?zz are independent, and in the long-wavelength static limit they yield results in accordance with the RPA scheme. The plasma dispersion law for long wavelength is also found to be identical in the MC and RPA scheme. In the ferromagnetic case, one of the MC schemes gives the same results as the RPA results for the Stoner model, and very different results for the Coulomb gas. The long-wavelength spin-wave dispersion is found to be different in the two schemes. A new nonlocal-zero-moment-conserving scheme is set up which gives the same equations as the RPA. It is thus concluded that a local-MC scheme is different from the RPA by virtue of the actual structure of the correlation functions, even though in the paramagnetic limit the results are similar for the static long-wavelength limit.

A. K. Rajagopal, J. Rath, and John C. Kimball

1973-03-15T23:59:59.000Z

17

Muon-spin-rotation studies of organic magnets  

Science Journals Connector (OSTI)

...organized by P. Day and A. E. Underhill Muon-spin-rotation studies of organic magnets...Laboratory, Parks Road, Oxford OX1 3PU, UK A muon is an unstable spin- particle with a lifetime...s. Beams of spin-polarized positive muons can be prepared at accelerator facilities...

1999-01-01T23:59:59.000Z

18

Magnetic charge crystals imaged in artificial spin ice  

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

Magnetic charge crystals imaged in artificial spin ice Magnetic charge crystals imaged in artificial spin ice Magnetic charge crystals imaged in artificial spin ice Potential data storage and computational advances could follow August 27, 2013 Potential data storage and computational advances could follow A 3-D depiction of the honeycomb artificial spin ice topography after the annealing and cooling protocols. The light and dark colors represent the north and south magnetic poles of the islands. Image by Ian Gilbert, U. of I. Department of Physics and Frederick Seitz Materials Research Laboratory Contact Nancy Ambrosiano Communications Office (505) 667-0471 Email Siv Schwink U. Illinois (217) 300-2201 Email "The emergence of magnetic monopoles in spin ice systems is a particular case of what physicists call fractionalization, or deconfinement of

19

Poissonian Behavior of Ising Spin Systems in an External Field  

E-Print Network [OSTI]

Poissonian Behavior of Ising Spin Systems in an External Field A. Ganesh 1 , B. M. Hambly 2 , Neil approximation to spin-half Ising- type models, in positive external #12;eld, which satisfy the FKG inequality and nearest-neighbour ferromagnetic Ising models. KEY WORDS: Poisson approximation, Stein-Chen method, Ising

Upton, Paul

20

Dynamic Switching of the Spin Circulation in Tapered Magnetic Nanodisks  

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

Dynamic Switching of the Spin Dynamic Switching of the Spin Circulation in Tapered Magnetic Nanodisks Dynamic Switching of the Spin Circulation in Tapered Magnetic Nanodisks Print Monday, 22 April 2013 12:09 fischer-magnetic vortices Ferromagnetic NiFe disks (500-nm-wide and 20-nm-thick), were fabricated by e-beam lithography onto a waveguide structure. Field pulses, generated by launching current pulses into the waveguide trigger the magnetization dynamics in the elements. Using the soft x-ray microscope XM-1 providing 25-nm spatial resolution, circularly polarized soft x-rays give rise to XMCD contrast which allows to record an image of the in-plane circulation of the magnetic vortex. The topology of vortices-areas where there is a spinning motion around an imaginary axis-is a physical phenomenon which is found across a large

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Pulsed Nuclear Magnetic Resonance: Spin Echoes MIT Department of Physics  

E-Print Network [OSTI]

Pulsed Nuclear Magnetic Resonance: Spin Echoes MIT Department of Physics (Dated: February 5, 2014) In this experiment, the phenomenon of Nuclear Magnetic Resonance (NMR) is used to determine the magnetic moments-factor in atomic spectroscopy and is given by g = (µ/µN )/I, (2) and µN is the nuclear magneton, e /2mp

Seager, Sara

22

Spin torque in magnetic tunnel junctions with asymmetric barriers  

Science Journals Connector (OSTI)

We derive expressions for both parallel and perpendicular components of spin transfer torque (STT) in magnetic tunnel junctions (MTJs), which have several important advantages over the currently available expressions: First they are derived in a more realistic approximation, resulting in excellent agreement with exact results even in the presence of resonant tunneling. Second, we show that they can be expressed in terms of the scattering matrix elements, which gives them a clear physical interpretation. Third, they are given entirely in terms of collinear quantities, which are readily available in existing transport codes. We use these expressions to investigate STT behavior in MTJs with asymmetric barriers at finite bias. The results show that lowering the barrier height in the bulk does not qualitatively change the behavior of STT. The absolute STT increases on account of the overall increase of the barrier transparency; however, the STT efficiency remains in the same range. At the same time, modifications of the interfaces can qualitatively change STT behavior. Thus, interface engineering can be used to control the bias dependence of STT and optimize the performance of STT-based devices.

Alan Kalitsov; Whasington Silvestre; Mairbek Chshiev; Julian P. Velev

2013-09-30T23:59:59.000Z

23

Microscopic reversal behavior of magnetically capped nanospheres  

Science Journals Connector (OSTI)

The magnetic switching behavior of Co/Pd multilayer-capped nanospheres is investigated by x-ray spectro-holography. Images of the magnetic state of individual nanocaps are recorded as a function of externally applied magnetic field and the angle under which the field is applied, pertaining to magnetic data storage applications with patterned, tilted, and perpendicular storage media. Dispersed nanospheres with different coverage in the submonolayer regime are investigated simultaneously in a multiplexed experiment. In clustered nanosphere arrangements, we find that individual switching events are influenced by dipolar magnetostatic interactions. Micromagnetic simulations of the switching behavior complement the experimental observations, corroborating the influence of thermal activation processes and magnetostatic interactions in this system. Such magnetostatic interactions could lead to undesired cross-talk between bits in ultrahigh-density magnetic recording applications.

C. M. Günther; O. Hellwig; A. Menzel; B. Pfau; F. Radu; D. Makarov; M. Albrecht; A. Goncharov; T. Schrefl; W. F. Schlotter; R. Rick; J. Lüning; S. Eisebitt

2010-02-17T23:59:59.000Z

24

Re-entrant Spin Glass Behavior in Mn-rich YMnO3  

SciTech Connect (OSTI)

We use magnetism and specific heat measurements to investigate the hexagonal Mn-rich YMnO{sub 3}. It is found that upon cooling from a high temperature, the compound first orders antiferromagnetically at T{sub N} {approx} 72 K and then undergoes a re-entrant spin glass (RSG) transition at T{sub SG} {approx} 42 K. This RSG behavior results from the competition between the ferromagnetic interaction and the antiferromagnetic interaction, which is related to the intrinsic geometric magnetic frustration in this system.

Chen, W. R. [Chinese Academy of Sciences; Zhang, F. C. [Chinese Academy of Sciences; Miao, J. [Chinese Academy of Sciences; Xu, B. [Chinese Academy of Sciences; Dong, X. L. [Chinese Academy of Sciences; Cao, L. X. [Chinese Academy of Sciences; Qiu, X. G. [Chinese Academy of Sciences; Zhao, Bairu [Chinese Academy of Sciences; Dai, Pengcheng [University of Tennessee, Knoxville (UTK)

2005-01-01T23:59:59.000Z

25

Magnetic field sensors using 13-spin cat states  

E-Print Network [OSTI]

Measurement devices could benefit from entangled correlations to yield a measurement sensitivity approaching the physical Heisenberg limit. Building upon previous magnetometric work using pseudo-entangled spin states in solution-state NMR, we present two conceptual advancements to better prepare and interpret the pseudo-entanglement resource as well as the use of a 13-spin cat state to measure the local magnetic field with a sensitivity beyond the standard quantum limit.

Stephanie Simmons; Jonathan A. Jones; Steven D. Karlen; Arzhang Ardavan; John J. L. Morton

2010-11-24T23:59:59.000Z

26

Universality of spin relaxation for spin-1/2 particles diffusing over magnetic-field inhomogeneities in the adiabatic regime  

Science Journals Connector (OSTI)

We present a theoretical analysis of spin relaxation, for a polarized gas of spin 1/2 particles undergoing restricted adiabatic diffusive motion within a container of arbitrary shape, due to magnetic field inhomogeneities of arbitrary form.

M. Guigue; G. Pignol; R. Golub; A. K. Petukhov

2014-07-09T23:59:59.000Z

27

Electromagnetic soliton-particle with spin and magnetic moment  

E-Print Network [OSTI]

Electromagnetic soliton-particle with both quasi-static and quick-oscillating wave parts is considered. Its mass, spin, charge, and magnetic moment appear naturally when the interaction with distant solitons is considered. The substantiation of Dirac equation for the wave part of the interacting soliton-particle is given.

Alexander A. Chernitskii

2012-12-17T23:59:59.000Z

28

Oxygen-induced magnetic properties and metallic behavior of a...  

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

Oxygen-induced magnetic properties and metallic behavior of a BN sheet. Oxygen-induced magnetic properties and metallic behavior of a BN sheet. Abstract: In this paper, ab initio...

29

Superconducting magnetic Wollaston prism for neutron spin encoding  

SciTech Connect (OSTI)

A magnetic Wollaston prism can spatially split a polarized neutron beam into two beams with different neutron spin states, in a manner analogous to an optical Wollaston prism. Such a Wollaston prism can be used to encode the trajectory of neutrons into the Larmor phase associated with their spin degree of freedom. This encoding can be used for neutron phase-contrast radiography and in spin echo scattering angle measurement (SESAME). In this paper, we show that magnetic Wollaston prisms with highly uniform magnetic fields and low Larmor phase aberration can be constructed to preserve neutron polarization using high temperature superconducting (HTS) materials. The Meissner effect of HTS films is used to confine magnetic fields produced electromagnetically by current-carrying HTS tape wound on suitably shaped soft iron pole pieces. The device is cooled to ?30 K by a closed cycle refrigerator, eliminating the need to replenish liquid cryogens and greatly simplifying operation and maintenance. A HTS film ensures that the magnetic field transition within the prism is sharp, well-defined, and planar due to the Meissner effect. The spin transport efficiency across the device was measured to be ?98.5% independent of neutron wavelength and energizing current. The position-dependent Larmor phase of neutron spins was measured at the NIST Center for Neutron Research facility and found to agree well with detailed simulations. The phase varies linearly with horizontal position, as required, and the neutron beam shows little depolarization. Consequently, the device has advantages over existing devices with similar functionality and provides the capability for a large neutron beam (20 mm × 30 mm) and an increase in length scales accessible to SESAME to beyond 10 ?m. With further improvements of the external coupling guide field in the prototype device, a larger neutron beam could be employed.

Li, F., E-mail: fankli@indiana.edu; Parnell, S. R.; Wang, T.; Baxter, D. V. [Center for Exploration of Energy and Matter, Indiana University, Bloomington, Indiana 47408 (United States)] [Center for Exploration of Energy and Matter, Indiana University, Bloomington, Indiana 47408 (United States); Hamilton, W. A. [Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States)] [Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States); Maranville, B. B. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)] [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Semerad, R. [Ceraco Ceramic Coating GmbH, Ismaning 85737 (Germany)] [Ceraco Ceramic Coating GmbH, Ismaning 85737 (Germany); Cremer, J. T. [Adelphi Technology Inc., Redwood City, California 94063 (United States)] [Adelphi Technology Inc., Redwood City, California 94063 (United States); Pynn, R. [Center for Exploration of Energy and Matter, Indiana University, Bloomington, Indiana 47408 (United States) [Center for Exploration of Energy and Matter, Indiana University, Bloomington, Indiana 47408 (United States); Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States)

2014-05-15T23:59:59.000Z

30

Thermal spin-transfer torque in magnetic tunnel junctions (invited)  

SciTech Connect (OSTI)

The thermal spin-transfer torque (TSTT) is an effect to switch the magnetic free layer in a magnetic tunnel junction by a temperature gradient only. We present ab initio calculations of the TSTT. In particular, we discuss the influence of magnetic layer composition by considering Fe{sub x}Co{sub 1–x} alloys. Further, we compare the TSTT to the bias voltage driven STT and discuss the requirements for a possible thermal switching. For example, only for very thin barriers of 3 monolayers MgO, a thermal switching is imaginable. However, even for such a thin barrier, the TSTT is still too small for switching at the moment and further optimization is needed. In particular, the TSTT strongly depends on the composition of the ferromagnetic layer. In our current study, it turns out that at the chosen thickness of the ferromagnetic layer, pure Fe gives the highest thermal spin-transfer torque.

Heiliger, Christian, E-mail: christian.heiliger@physik.uni-giessen.de; Franz, C.; Czerner, Michael [I. Physikalisches Institut, Justus Liebig University, Giessen (Germany)

2014-05-07T23:59:59.000Z

31

Magnetization and spin diffusion of liquid He3 in aerogel  

Science Journals Connector (OSTI)

We report theoretical calculations and experimental measurements of the normal-state spin diffusion coefficient of He3 in aerogel, including both elastic and inelastic scattering of He3 quasiparticles, and compare these results with data for He3 in 98% porous silica aerogel. This analysis provides a determination of the elastic mean free path within the aerogel. Measurements of the magnetization of the superfluid phase in the same aerogel samples provide a test of the theory of pairbreaking and magnetic response of low-energy excitations in the “dirty” B phase of He3 in aerogel. A consistent interpretation of the data for the spin-diffusion coefficient, magnetization, and superfluid transition temperature is obtained by including correlation effects in the aerogel density.

J. A. Sauls; Yu. M. Bunkov; E. Collin; H. Godfrin; P. Sharma

2005-07-07T23:59:59.000Z

32

Spin-polarized transport through domain wall in magnetized graphene  

E-Print Network [OSTI]

Atomically thin two-dimensional layer of honeycomb crystalline carbon known as graphene is a promising system for electronics. It has a point-like Fermi surface, which is very sensitive to external potentials. In particular, Zeeman magnetic field parallel to the graphene layer splits electron bands and creates fully spin-polarized and geometrically congruent circular Fermi surfaces of particle and hole type. In the presence of electric field, particles and holes with opposite spins drift in opposite direction. These phenomena are likely to be of interest for developing graphene-based spintronic devices. A domain wall (DW) separating regions with opposite spin polarizations is a basic element of such a device. Here we consider a ballistic passage of spin-polarized charge carriers through DW in graphene. We also discuss the analogy between the generation of spin currents in graphene and in relativistic quark-gluon plasma, where the spin-polarized current is responsible for the phenomenon of charge separation studied recently at RHIC.

M. Khodas; I. A. Zaliznyak; D. E. Kharzeev

2009-04-08T23:59:59.000Z

33

High-precision description and new properties of a spin-1 particle in a magnetic field  

E-Print Network [OSTI]

The exact Foldy-Wouthuysen Hamiltonian is derived for a pointlike spin-1 particle with a normal magnetic moment in a nonuniform magnetic field. For a uniform magnetic field, it is exactly separated into terms linear and quadratic in spin. New unexpected properties of a particle with an anomalous magnetic moment are found. Spin projections of a particle moving in a uniform magnetic field are not integer and the tensor polarization is asymmetric in the plane orthogonal to the field. Previously described spin-tensor effects caused by the tensor magnetic polarizability exist not only for nuclei but also for pointlike particles.

Alexander J. Silenko

2014-04-19T23:59:59.000Z

34

Spin Magnetic Resonance in Perspectives of Spin Science and Spin Technology Development  

Science Journals Connector (OSTI)

The methods of magnetic resonance are widely used in many fields ... the pages of a specialized journal “Applied Magnetic Resonance”. This is even more important ... of MR methods in somewhat unusual fields of science

Kev M. Salikhov

2014-09-01T23:59:59.000Z

35

IEEE TRANSACTIONS ON MAGNETICS, VOL. 47, NO. 6, JUNE 2011 1545 Spin Injection Into Magnesium Nanowire  

E-Print Network [OSTI]

IEEE TRANSACTIONS ON MAGNETICS, VOL. 47, NO. 6, JUNE 2011 1545 Spin Injection Into Magnesium and Technology Beijing, Beijing 100083, China Spin injection into magnesium from Permalloy is performed nanowires. The short spin diffusion length of magnesium which has a small spin-orbit interaction can

Otani, Yoshichika

36

Size Effect in the Spin Glass Magnetization of Thin AuFe Films as Studied by Polarized Neutron Reflectometry  

Science Journals Connector (OSTI)

We used polarized neutron reflectometry to determine the temperature dependence of the magnetization of thin AuFe films with 3% Fe concentration. We performed the measurements in a large magnetic field of 6 T in a temperature range from 295 to 2 K. For the films in the thickness range from 500 to 20 nm we observed a Brillouin-type behavior from 295 K down to 50 K and a constant magnetization of about 0.9?B per Fe atom below 30 K. However, for the 10 nm thick film we observed a Brillouin-type behavior down to 20 K and a constant magnetization of about 1.3?B per Fe atom below 20 K. These experiments are the first to show a finite-size effect in the magnetization of single spin-glass films in large magnetic fields. Furthermore, the ability to measure the deviation from the paramagnetic behavior enables us to prove the existence of the spin-glass state where other methods relying on a cusp-type behavior fail.

M. Saoudi; H. Fritzsche; G. J. Nieuwenhuys; M. B. S. Hesselberth

2008-02-06T23:59:59.000Z

37

The Nuclear Spin and Magnetic Moment of Potassium (41)  

Science Journals Connector (OSTI)

The spin of the K41 nucleus and the h.f.s. separation of the S122 normal state have been measured by the method of zero moments. The high resolution necessary to separate the two isotopes was obtained by passing a beam of neutral potassium atoms through a weak inhomogeneous magnetic field 153 cm long. The total beam length was 201 cm. A new method of analysis of the zero moment peak of K41 in relation to that of K39 was used in the determination of the spin. The spin was found to be 3/2 and the h.f.s. separation to be 0.554±0.2 percent of that of K39. The same ratio applies to the magnetic moments, hence this ratio and the values for K39 given by Fox and Rabi yield {??(K41),=0.00853±0.0001 cm-1}{?(K41),=0.22 nuclear Bohr magneton .} From the peak intensities it is possible to give the abundance ratio K39/K41 as 13.4±0.5.

J. H. Manley

1936-06-15T23:59:59.000Z

38

Ising spin glass in a transverse magnetic field  

Science Journals Connector (OSTI)

We study the three-dimensional quantum Ising spin glass in a transverse magnetic field following the evolution of the bond probability distribution under renormalization-group transformations. The phase diagram (critical temperature Tc vs transverse field ?) we obtain shows a finite slope near T=0, in contrast with the infinite slope for the pure case. Our results compare very well with the experimental data recently obtained for the dipolar Ising spin glass LiHo0.167Y0.833F4, in a transverse field. This indicates that this system is more appropriately described by a model with short-range interactions than by an equivalent Sherrington-Kirkpatrick model in a transverse field.

Beatriz Boechat, Raimundo R. dos Santos, and M. A. Continentino

1994-03-01T23:59:59.000Z

39

Spin glass behavior in an interacting -Fe2O3 nanoparticle system D. Parker*1  

E-Print Network [OSTI]

- 1 - Spin glass behavior in an interacting -Fe2O3 nanoparticle system D. Parker*1 , V. Dupuis+2 glass behavior of a concentrated assembly of interacting maghemite nanoparticles and compare it to that of canonical atomic spin glass systems. ac versus temperature and frequency measurements show evidence

Boyer, Edmond

40

Memory effect and temperature behavior in spin valves with and without antiferromagnetic subsystems  

E-Print Network [OSTI]

Memory effect and temperature behavior in spin valves with and without antiferromagnetic subsystems Temperature behavior and memory effect in standard spin valves SV and SVs with synthetic antiferromagnetic Co/Ru/Co SV-SAF subsystems have been studied. SV-SAFs show much better temperature stability. Memory effect

Xiao, John Q.

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Determining the exchange parameters of spin-1 metal-organic molecular magnets in pulsed magnetic fields  

SciTech Connect (OSTI)

We nave measured the high-field magnetization of a number of Ni-based metal-organic molecular magnets. These materials are self-assembly coordination polymers formed from transition metal ions and organic ligands. The chemistry of the compounds is versatile allowing many structures with different magnetic properties to be formed. These studies follow on from previous measurements of the Cu-based analogues in which we showed it was possible to extract the exchange parameters of low-dimensional magnets using pulsed magnetic fields. In our recent experiments we have investigated the compound (Ni(HF{sub 2})(pyz){sub 2})PF{sub 6}, where pyz = pyrazine, and the Ni-ions are linked in a quasi-two-dimensional (Q2D) square lattice via the pyrazine molecules, with the layers held together by HF{sub 2} ligands. We also investigated Ni(NCS){sub 2}(pyzdo){sub 2}, where pyzdo = pyrazine dioxide. The samples are grown at Eastern Washington University using techniques described elsewhere. Measurements are performed at the pulsed magnetic field laboratory in Los Alamos. The magnetization of powdered samples is determined using a compensated coil magnetometer in a 65 T short pulse magnet. Temperatures as low as 500 mK are achievable using a {sup 3}He cryostat. The main figure shows the magnetization of the spin-1 [Ni(HF{sub 2})(pyz){sub 2}]PF{sub 6} compound at 1.43 K. The magnetization rises slowly at first, achieving a rounded saturation whose midpoint is around 19 T. A small anomaly is also seen in the susceptibility at low fields ({approx}3 T), which might be attributed to a spin-flop transition. In contrast, the spin-1/2 [Cu(HF{sub 2})(pyz){sub 2}]PF{sub 6} measured previously has a saturation magnetization of 35.5 T and a strongly concave form of M(B) below this field. This latter compound was shown to be a good example of a Q2D Heisenberg antiferromagnet with the strong exchange coupling (J{sub 2D} = 12.4 K, J{sub {perpendicular}}/J{sub 2D} {approx} 10{sup -2}) directed along the Cu-pyz-Cu directions. The structure of the two compounds is similar, but in the case of the Cu-compound the Cu-Cu pathways are linear, whereas in the Ni-compound they are kinked. The pulsed-field data combined with information from temperature-dependent susceptibility, muon-spin rotation, electron-spin resonance and ligand-field calculations suggest that, far from being magnetically Q2D, the Ni-compound is fairly one-dimensional with the dominant exchange (J{sub 1D} = 3.1 K and J{sub {perpendicular}}/J{sub 1D} = 0.63) directed along the Ni-FHF-Ni direction. Ni(NCS){sub 2}(pyzdo){sub 2} was also investigated. Previous ultra-high field measurements using the 100 T magnet have shown that this compound has a saturation field close to 80 T. The purpose of the present studies is to map out the phase diagram of this material at mid-range fields. The data are shown in the inset to the figure. This continuing project probes the ability of organic ligands to mediate magnetic exchange, the link between structure, dimensionality and bulk magnetic properties, as well as the role of spin number in quantum magnets. Ultimately the investigations aim to determine to what extent it is possible to produce self-assembly molecular materials with tailor-made magnetic characteristics.

Mcdonald, Ross D [Los Alamos National Laboratory; Singleton, John [Los Alamos National Laboratory; Lancaster, Tom [OXFORD UNIV.; Goddard, Paul [OXFORD UNIV.; Manson, Jamie [EASTERN WASHINGTON UNIV.

2011-01-14T23:59:59.000Z

42

Magnetic field induced discontinuous spin reorientation in ErFeO{sub 3} single crystal  

SciTech Connect (OSTI)

The spin reorientation of ErFeO{sub 3} that spontaneously occurs at low temperature has been previously determined to be a process involving the continuous rotation of Fe{sup 3+} spins. In this work, the dynamic process of spin reorientation in ErFeO{sub 3} single crystal has been investigated by AC susceptibility measurements at various frequencies and static magnetic fields. Interestingly, two completely discontinuous steps are induced by a relatively large static magnetic field due to the variation in the magnetic anisotropy during this process. It provides deeper insights into the intriguing magnetic exchange interactions which dominate the sophisticated magnetic phase transitions in the orthoferrite systems.

Shen, Hui [School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418 (China) [School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2500 (Australia); Cheng, Zhenxiang, E-mail: cheng@uow.edu.au; Hong, Fang; Wang, Xiaolin [Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2500 (Australia)] [Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2500 (Australia); Xu, Jiayue [School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418 (China)] [School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Yuan, Shujuan; Cao, Shixun [Department of Physics, Shanghai University, Shanghai 200444 (China)] [Department of Physics, Shanghai University, Shanghai 200444 (China)

2013-11-04T23:59:59.000Z

43

Neutron resonance spin echo, bootstrap method for increasing the effective magnetic field  

E-Print Network [OSTI]

1195 Neutron resonance spin echo, bootstrap method for increasing the effective magnetic field R donné en spectrométrie d'echos de spins de neutrons. Les limites théoriques et techniques à l field intensity in Neutron Resonance Spin Echo (NRSE) spectrometry. The limits, theoretical as well

Paris-Sud XI, Université de

44

Monte Carlo Study of the Spin Transport in Magnetic Materials , K. Akablia,b  

E-Print Network [OSTI]

Monte Carlo Study of the Spin Transport in Magnetic Materials Y. Magnina , K. Akablia,b , H. T of Natural Science and Technology, Okayama University 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.. Abstract The resistivity in magnetic materials has been theoretically shown to depend on the spin

45

Spin-polarized current oscillations in diluted magnetic semiconductor multiple quantum wells Manuel Bejar,1  

E-Print Network [OSTI]

. The transport properties of Mn-based heterostructures have been studied10 including miniband transportSpin-polarized current oscillations in diluted magnetic semiconductor multiple quantum wells Manuel. The spin polarization oscillates in both magnetic and nonmagnetic quantum wells and the time average

Sánchez, David

46

Spin transport in inhomogeneous magnetic fields:?A proposal for Stern-Gerlach-like experiments with conduction electrons  

Science Journals Connector (OSTI)

Spin dynamics in spatially inhomogeneous magnetic fields is studied within the framework of Boltzmann theory. Stern-Gerlach-like separation of spin up and spin down electrons occurs in ballistic and diffusive regimes, before spin relaxation sets in. Transient dynamics and spectral response to time-dependent inhomogeneous magnetic fields are investigated, and possible experimental observations of our findings are discussed.

Jaroslav Fabian and S. Das Sarma

2002-07-26T23:59:59.000Z

47

Behavior of nanoparticle clouds around a magnetized microsphere under magnetic and flow fields  

E-Print Network [OSTI]

1 Behavior of nanoparticle clouds around a magnetized microsphere under magnetic and flow fields-sized magnetizable particle is introduced into a suspension of nanosized magnetic particles, the nanoparticles and allows efficient magnetic separation of nanoparticles used in bioanalysis and water purification

Paris-Sud XI, Université de

48

Antiferromagnet-based nuclear spin model of scalable quantum register with inhomogeneous magnetic field  

E-Print Network [OSTI]

As a nuclear spin model of scalable quantum register, the one-dimensional chain of the magnetic atoms with nuclear spins 1/2 substituting the basic atoms in the plate of nuclear spin free easy-axis 3D antiferromagnet is considered. It is formulated the generalized antiferromagnet Hamiltonian in spin-wave approximation (low temperatures) considering the inhomogeneous external magnetic field, which is directed along the easy axis normally to plane of the plate and has a constant gradient along the nuclear spin chain. Assuming a weak gradient, the asymptotic expression for coefficients of unitary transformations to the diagonal form of antiferromagnet Hamiltonian is found. With this result the expression for indirect interspin coupling, which is due to hyperfine nuclear electron coupling in atoms and the virtual spin wave propagation in antiferromagnet ground state, was evaluated. It is shown that the inhomogeneous magnetic field essentially modifies the characteristics of indirect interspin coupling. The indirect interaction essentially grows and even oscillates in relation to the interspin distance when the local field value in the middle point of two considered nuclear spin is close to the critical field for quantum phase transition of spin-flop type in bulk antiferromagnet or close to antiferromagnetic resonance. Thus, the external magnetic field, its gradient, microwave frequency and power can play the role of control parameters for qubit states. Finally, the one and two qubit states decoherence and longitudinal relaxation rate are caused by the interaction of nuclear spins with virtual spin waves in antiferromagnet ground state are calculated.

A. A. Kokin; V. A. Kokin

2008-12-01T23:59:59.000Z

49

Spinning a New Type of Magnetic Field | U.S. DOE Office of Science (SC)  

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

Spinning a New Type of Magnetic Field Spinning a New Type of Magnetic Field Basic Energy Sciences (BES) BES Home About Research Facilities Science Highlights Benefits of BES Funding Opportunities Basic Energy Sciences Advisory Committee (BESAC) News & Resources Contact Information Basic Energy Sciences U.S. Department of Energy SC-22/Germantown Building 1000 Independence Ave., SW Washington, DC 20585 P: (301) 903-3081 F: (301) 903-6594 E: sc.bes@science.doe.gov More Information » October 2013 Spinning a New Type of Magnetic Field Harnessing the spins of electrons in a new way - enabling efficient magnetic switching and holding promise for spintronic devices. Print Text Size: A A A Subscribe FeedbackShare Page Click to enlarge photo. Enlarge Photo Image courtesy of John Xiao Schematic of mechanism for generating a magnetic field. The system consists

50

Magnetic structures, phase diagram and spin waves of magneto-electric  

E-Print Network [OSTI]

Magnetic structures, phase diagram and spin waves of magneto-electric LiNiPO4 Thomas Bagger Stibius Roskilde, Denmark June 2007 #12;Author: Thomas Bagger Stibius Jensen Title: Magnetic structures, phase, having co-existing antiferromagnetic and ferroelectric phases when suitable magnetic fields are applied

51

Observation of spin-wave dispersion in Nd-Fe-B magnets using neutron Brillouin scattering  

SciTech Connect (OSTI)

The low-energy spin-wave dispersion in polycrystalline Nd-Fe-B magnets was observed using neutron Brillouin scattering (NBS). Low-energy spin-wave excitations for the lowest acoustic spin-wave mode were clearly observed. From the spin-wave dispersion, we were able to determine the spin-wave stiffness constant D{sub sw} (100.0?±?4.9?meV.Å{sup 2}) and the exchange stiffness constant A (6.6 ± 0.3 pJ/m)

Ono, K., E-mail: kanta.ono@kek.jp; Inami, N.; Saito, K.; Takeichi, Y.; Kawana, D.; Yokoo, T.; Itoh, S. [Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Yano, M.; Shoji, T.; Manabe, A.; Kato, A. [Toyota Motor Corporation, Toyota, Aichi 471-8571 (Japan); Kaneko, Y. [Toyota Central R and D Labs. Inc., Aichi 480-1192 (Japan)

2014-05-07T23:59:59.000Z

52

Dynamic control of spin states in interacting magnetic elements  

DOE Patents [OSTI]

A method for the control of the magnetic states of interacting magnetic elements comprising providing a magnetic structure with a plurality of interacting magnetic elements. The magnetic structure comprises a plurality of magnetic states based on the state of each interacting magnetic element. The desired magnetic state of the magnetic structure is determined. The active resonance frequency and amplitude curve of the desired magnetic state is determined. Each magnetic element of the magnetic structure is then subjected to an alternating magnetic field or electrical current having a frequency and amplitude below the active resonance frequency and amplitude curve of said desired magnetic state and above the active resonance frequency and amplitude curve of the current state of the magnetic structure until the magnetic state of the magnetic structure is at the desired magnetic state.

Jain, Shikha; Novosad, Valentyn

2014-10-07T23:59:59.000Z

53

Giant Viscosity Enhancement in a Spin-Polarized Fermi Liquid National High Magnetic Field Laboratory  

E-Print Network [OSTI]

electrons, ultra-cold atoms, and 3He-4He mixtures. If the magnetic field is sufficiently high so~ 15 T, T~ 2mk), for which the spin polarization attains values greater than 99%. Akimoto, H.; Xia, J

Weston, Ken

54

Spin Torques in Magnetic and Superconducting Tunnel Junctions  

E-Print Network [OSTI]

Josephson Junctions . . . . . . . . . . . . . . . . . . . . .Nonlinear Dynamics in a Magnetic Josephson Junction . . . .in a magnetic Josephson junction. ” Phys. Rev. B, 86:

Hoffman, Silas Eli

2012-01-01T23:59:59.000Z

55

Sub-nanometer resolution in three-dimensional magnetic-resonance imaging of individual dark spins  

E-Print Network [OSTI]

Magnetic resonance imaging (MRI) has revolutionized biomedical science by providing non-invasive, three-dimensional biological imaging. However, spatial resolution in conventional MRI systems is limited to tens of microns, which is insufficient for imaging on molecular and atomic scales. Here we demonstrate an MRI technique that provides sub-nanometer spatial resolution in three dimensions, with single electron-spin sensitivity. Our imaging method works under ambient conditions and can measure ubiquitous 'dark' spins, which constitute nearly all spin targets of interest and cannot otherwise be individually detected. In this technique, the magnetic quantum-projection noise of dark spins is measured using a single nitrogen-vacancy (NV) magnetometer located near the surface of a diamond chip. The spatial distribution of spins surrounding the NV magnetometer is imaged with a scanning magnetic-field gradient. To evaluate the performance of the NV-MRI technique, we image the three-dimensional landscape of dark electronic spins at and just below the diamond surface and achieve an unprecedented combination of resolution (0.8 nm laterally and 1.5 nm vertically) and single-spin sensitivity. Our measurements uncover previously unidentified electronic spins on the diamond surface, which can potentially be used as resources for improved magnetic imaging of samples proximal to the NV-diamond sensor. This three-dimensional NV-MRI technique is immediately applicable to diverse systems including imaging spin chains, readout of individual spin-based quantum bits, and determining the precise location of spin labels in biological systems.

M. S. Grinolds; M. Warner; K. De Greve; Y. Dovzhenko; L. Thiel; R. L. Walsworth; S. Hong; P. Maletinsky; A. Yacoby

2014-01-12T23:59:59.000Z

56

SU(2s+1) symmetry and nonlinear dynamic equations of spin s magnets  

E-Print Network [OSTI]

The article is devoted to the description of dynamics of magnets with arbitrary spin on the basis of the Hamiltonian formalism. The relationship between the magnetic ordering and Poisson bracket subalgebras of the magnetic degrees of freedom for spin s=1/2; 1; 3/2 has been established. We have been obtained non-linear dynamic equations without damping for normal and degenerate non-equilibrium states of high-spin magnets with the properties of the SO(3), SU(4), SU(2)$\\times$SU(2), SU(3), SO(4), SO(5) symmetry of exchange interaction. The connection between models of the magnetic exchange energy and the Casimir invariants has been discussed.

M. Y. Kovalevsky; A. V. Glushchenko

2013-12-20T23:59:59.000Z

57

Critical behavior and universality in Levy spin glasses  

E-Print Network [OSTI]

or bimodal-distributed interactions. Corrections to scaling are large for Levy spin glasses. To overcome these and show that the critical exponents agree with the bimodal and Gaussian case, we perform an extended scaling of the two-point finite...

Andresen, Juan Carlos; Janzen, Katharina; Katzgraber, Helmut G.

2011-01-01T23:59:59.000Z

58

Generation of a spin-polarized electron beam by multipoles magnetic fields  

E-Print Network [OSTI]

The propagation of an electron beam in the presence of transverse magnetic fields possessing integer topological charges is presented. The spin--magnetic interaction introduces a nonuniform spin precession of the electrons that gains a space-variant geometrical phase in the transverse plane proportional to the field's topological charge, whose handedness depends on the input electron's spin state. A combination of our proposed device with an electron orbital angular momentum sorter can be utilized as a spin-filter of electron beams in a mid-energy range. We examine these two different configurations of a partial spin-filter generator numerically. The results of these analysis could prove useful in the design of improved electron microscope.

Ebrahim Karimi; Vincenzo Grillo; Robert W. Boyd; Enrico Santamato

2013-06-10T23:59:59.000Z

59

Incoherent interaction of propagating spin waves with precessing magnetic moments  

E-Print Network [OSTI]

The magnetization dynamics of the magnetic vortex state occurring in response to subnanosecond transitions of the externally applied magnetic field was investigated in Ni[subscript 80]Fe[subscript 20](12?nm)/Ir[subscript ...

Ross, Caroline A.

60

Extended coherence length of spatially oscillating electron-spin polarization in dilute-magnetic-semiconductor quantum wells  

SciTech Connect (OSTI)

We have investigated the possibility that the coherence length of spatially oscillating electron-spin polarization is improved in dilute magnetic semiconductors. In usual nonmagnetic quantum wells, the spin polarization of the electrons injected from a ferromagnetic source electrode oscillates spatially because of the spin precession due to spin-orbit effective magnetic fields, i.e., the Rashba and Dresselhaus fields. However, the polarization is damped within an oscillation period by the D’yakonov-Perel’ spin relaxation. In paramagnetic dilute magnetic semiconductors, impurity spin polarization is induced under the electron-spin polarization, and this impurity polarization influences the electron-spin precession and possibly improves the spatial electron-spin coherence. The validity of this effect is demonstrated by a numerical simulation for a CdMnTe quantum well.

Tsuchiya, Takuma [Division of Applied Physics, Faculty of Engineering, Hokkaido University (Hokudai), Sapporo 060-8628 (Japan)

2013-12-04T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Magnetic excitations and anomalous spin wave broadening in multiferroic FeV2O4  

SciTech Connect (OSTI)

FeV2O4 is found to show three structural transitions and successive paramagnetic(PM)- collinear ferrimagnetic(CFI)-nocollinear ferrimagnetic(NCFI) magnetic transitions. The tetragonal- orthorhombic structural transition associated with PM-CFI transition is accompanied by the ap- pearance of an energy gap with a high magnitude in the magnetic excitation spectrum, which is a consequence of the strong spin-orbital coupling induced anisotropy at Fe2+ A site. The comparison of Fe spin waves at CFI and noncollinear ferrimagnetic/ferroelectric phases shows no signicant spin frustration of Fe2+ spins at A site, suggesting A-site Fe2+ spins may not play a main role in the appearance of the ferroelectricity. Spin wave damping shows a rapid increase when NCFI transforms to CFI phase, indicating a possible V3+ spin uctuations at B site prior to their true canting in the NCFI phase. The spin wave broadening is also observed at the zone boundary without the spin wave softening, which is discussed in terms of the eect of magnon-phonon coupling. Understanding the

Zhang, Qiang [Ames Laboratory and Iowa State University; Ramazanoglu, Mehmet [Ames Laboratory; Chi, Songxue [ORNL; Liu, Yong [Ames Laboratory; Lograsso, Thomas [Ames Laboratory; Vaknin, David [Ames Laboratory

2014-01-01T23:59:59.000Z

62

Journal of Statistical Physics, Vol. 99, Nos. 12, 2000 Poissonian Behavior of Ising Spin Systems  

E-Print Network [OSTI]

Journal of Statistical Physics, Vol. 99, Nos. 1Ã?2, 2000 Poissonian Behavior of Ising Spin Systems-half Ising- type models in positive external field which satisfy the FKG inequality. In particular, we show Ising models. KEY WORDS: Poisson approximation; Stein Chen method; Ising models; nucleation. 1

O'Connell, Neil

63

Spin polarized neutron matte and magnetic susceptibility within the Brueckner-Hartree-Fock approximation  

E-Print Network [OSTI]

The Brueckner--Hartree--Fock formalism is applied to study spin polarized neutron matter properties. Results of the total energy per particle as a function of the spin polarization and density are presented for two modern realistic nucleon-nucleon interactions, Nijmegen II and Reid93. We find that the dependence of the energy on the spin polarization is practically parabolic in the full range of polarizations. The magnetic susceptibility of the system is computed. Our results show no indication of a ferromagnetic transition which becomes even more difficult as the density increases.

I. Vidaña; A. Polls; A. Ramos

2001-11-19T23:59:59.000Z

64

Magnetism reflectometer study shows LiF layers improve efficiency in spin valve devices  

SciTech Connect (OSTI)

New, more efficient materials for spin valves - a device used in magnetic sensors, random access memories, and hard disk drives - may be on the way based on research using the magnetism reflectometer at Oak Ridge National Laboratory (ORNL). Spin valve devices work by means of two or more conducting magnetic material layers that alternate their electrical resistance depending on the layers alignment. Giant magnetoresistance is a quantum mechanical effect first observed in thin film structures about 20 years ago. The effect is observed as a significant change in electrical resistance, depending on whether the magnetization of adjacent ferromagnetic layers is in a parallel or an antiparallel magnetic alignment. 'What we are doing here is developing new materials. The search for new materials suitable for injecting and transferring carriers with a preferential spin orientation is most important for the development of spintronics,' said Valeria Lauter, lead instrument scientist on the magnetism reflectometer at the Spallation Neutron Source (SNS), who collaborated on the experiment. The researchers discovered that the conductivity of such materials is improved when an organic polymer semiconductor layer is placed between the magnetic materials. Organic semiconductors are now the material of choice for future spin valve devices because they preserve spin coherence over longer times and distances than conventional semiconductors. While research into spin valves has been ongoing, research into organic semiconductors is recent. Previous research has shown that a 'conductivity mismatch' exists in spin valve systems in which ferromagnetic metal electrodes interface with such organic semiconductors as Alq3 ({pi}-conjugated molecule tris(8-hydroxy-quinoline) aluminium). This mismatch limits the efficient injection of the electrons from the electrodes at the interface with the semiconductor material. However, lithium fluoride (LiF), commonly used in light-emitting diodes, has been found to enhance the injection of electrons through the semiconductor. Researchers from the University of Alabama and ORNL used polarized neutrons at the magnetism reflectometer at SNS to investigate the electronic, magnetic, and structural properties of the electrodes in a novel system. In this system, the magnetic layers cobalt and Ni{sub 80}Fe{sub 20} are interfaced with spacer layers composed of the organic semiconductor Alq3. A coupling layer of LiF is inserted to separate the magnetized layers from the semiconductor. 'ALQ3 is an organic semiconductor material,' said Lauter. 'Normally in these systems a first magnetic layer is grown on a hard substrate so that one can get the controlled magnetic parameters. Then you grow the organic semiconductor layer, followed by another magnetic material layer, such as cobalt.' In addition to determining the effect of the LiF layers on the efficiency of the electron injection, the researchers wanted to determine the magnetic properties of the cobalt and Ni{sub 80}Fe{sub 20} as well as the interfacial properties: whether there is interdiffusion of cobalt through the LiF layer to the semiconductor, for example. The researchers used polarized neutrons at beam line 4A to probe the entire, layer-by-layer assembly of the system. 'Reflectometry with polarized neutrons is a perfect method to study thin magnetic films,' Lauter said. 'These thin films - if you put one on a substrate, you see it just like a mirror. However, this mirror has a very complicated internal multilayer structure. The neutrons look inside this complicated structure and characterize each and every interface. Due to the depth sensitivity of the method, we measure the structural and magnetic properties of each layer with the resolution of 0.5 nm. The neutron scattering results found that inserting LiF as a barrier significantly improves the quality of the interface, increasing the injection of electrons from the magnetic layer through the organic semiconductor in the spin valve and enhancing the overall properties of the system. In related work the magneti

Bardoel, Agatha A [ORNL; Lauter, Valeria [ORNL; Szulczewski, Greg J [ORNL

2012-01-01T23:59:59.000Z

65

Anisotropic exchange coupling in diluted magnetic semiconductors: Ab initio spin-density functional theory  

Science Journals Connector (OSTI)

A different scheme to calculate the exchange tensor J?ij describing in a phenomenological way the anisotropic exchange coupling of two moments in a magnetically ordered system is presented. The ab initio approach is based on spin-polarized relativistic multiple-scattering theory within the framework of spin-density functional theory. The scheme is applied to ferromagnetic CrTe as well as the diluted magnetic semiconductor system Ga1?xMnxAs. In the latter case the results show that there is a noticeable anisotropy in the exchange coupling present, although not as pronounced as those suggested in recent theoretical investigations.

H. Ebert and S. Mankovsky

2009-01-26T23:59:59.000Z

66

A study of magnetic anisotropy energy in CuMn spin glass  

E-Print Network [OSTI]

A STUDY OF MAGNETIC ANISOTROPY ENERGY IN CuMn SPIN GLASS A Thesis by CHRISTINE ADELE ALLEN Submitted to the Graduate College of Texas ARM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE August 1986... Major Subject: Physics A STUDY OF MAGNETIC ANISOTROPY ENERGY IN CuMn SPIN GLASS A Thesis by CHRISTINE ADELE ALLEN Approved as to style and content by: Thomas W. Adair, III (Chai man of Committee) Robert A. enefick (Member) Donald L. Parker...

Allen, Christine Adele

2012-06-07T23:59:59.000Z

67

Three-dimensional finite element modeling of a magnet array spinning above a conductor  

SciTech Connect (OSTI)

Drag forces due to eddy currents induced by the relative motion of a conductor and a magnetic field occur in many practical devices: motors, brakes, magnetic bearings, and magnetically levitated vehicles. Recently, finite element codes have included solvers for 3-D eddy current geometries and have the potential to be very useful in the design and analysis of these devices. In this paper, numerical results from three-dimensional modeling of a magnet array spinning above a conductor are compared to experimental results in order to assess the capabilities of these codes.

Lorimer, W.L.; Lieu, D.K. [Univ. of California, Berkeley, CA (United States). Dept. of Mechanical Engineering; Hull, J.R.; Mulcahy, T.M.; Rossing, T.D. [Argonne National Lab., IL (United States)

1993-12-31T23:59:59.000Z

68

Spin flux and magnetic solitons in an interacting two-dimensional electron gas: Topology of two-valued wave functions  

Science Journals Connector (OSTI)

It is suggested that an interacting many-electron system in a two-dimensional lattice may condense into a topological magnetic state distinct from any discussed previously. This condensate exhibits local spin-1/2 magnetic moments on the lattice sites but is composed of a Slater determinant of single-electron wave functions which exist in an orthogonal sector of the electronic Hilbert space from the sector describing traditional spin-density-wave or spiral magnetic states. These one-electron spinor wave functions have the distinguishing property that they are antiperiodic along a closed path encircling any elementary plaquette of the lattice. This corresponds to a 2? rotation of the internal coordinate frame of the electron as it encircles the plaquette. The possibility of spinor wave functions with spatial antiperiodicity is a direct consequence of the two-valuedness of the internal electronic wave function defined on the space of Euler angles describing its spin. This internal space is the topologically, doubly-connected, group manifold of SO(3). Formally, these antiperiodic wave functions may be described by passing a flux which couples to spin (rather than charge) through each of the elementary plaquettes of the lattice. When applied to the two-dimensional Hubbard model with one electron per site, this new topological magnetic state exhibits a relativistic spectrum for charged, quasiparticle excitations with a suppressed one-electron density of states at the Fermi level.For a topological antiferromagnet on a square lattice, with the standard Hartree-Fock, spin-density-wave decoupling of the on-site Hubbard interaction, there is an exact mapping of the low-energy one-electron excitation spectrum to a relativistic Dirac continuum field theory. In this field theory, the Dirac mass gap is precisely the Mott-Hubbard charge gap and the continuum field variable is an eight-component Dirac spinor describing the components of physical electron-spin amplitude on each of the four sites of the elementary plaquette in the original Hubbard model. Within this continuum model we derive explicitly the existence of hedgehog Skyrmion textures as local minima of the classical magnetic energy. These magnetic solitons carry a topological winding number ? associated with the vortex rotation of the background magnetic moment field by a phase angle 2?? along a path encircling the soliton. Such solitons also carry a spin flux of ?? through the plaquette on which they are centered. The ?=1 hedgehog Skyrmion describes a local transition from the topological (antiperiodic) sector of the one-electron Hilbert space to the nontopological sector. We derive from first principles the existence of deep level localized electronic states within the Mott-Hubbard charge gap for the ?=1 and 2 solitons. The spectrum of localized states is symmetric about E=0 and each subgap electronic level can be occupied by a pair of electrons in which one electron resides primarily on one sublattice and the second electron on the other sublattice. It is suggested that flux-carrying solitons and the subgap electronic structure which they induce are important in understanding the physical behavior of doped Mott insulators.

Sajeev John and Andrey Golubentsev

1995-01-01T23:59:59.000Z

69

Re-analysis of Magic Angle Spinning Nuclear Magnetic Resonance Determination of Interlamellar Waters in Lipid Bilayer Dispersions  

E-Print Network [OSTI]

Re-analysis of Magic Angle Spinning Nuclear Magnetic Resonance Determination of Interlamellar Waters in Lipid Bilayer Dispersions John F. Nagle,*# Yufeng Liu,* Stephanie Tristram-Nagle,# Richard M of multilamellar lipid vesicles using magic angle spinning nuclear magnetic resonance has been re

Nagle, John F.

70

Coupled spin models for magnetic variation of planets and stars  

Science Journals Connector (OSTI)

......The powers alpha are plotted in this diagram. The parameters lambda and mu are given...motivate our coupled spin model from general MHD. The element should have an inward-winding...applied the LCS model, supplemented with MHD equations, to other planets and satellites......

A. Nakamichi; H. Mouri; D. Schmitt; A. Ferriz-Mas; J. Wicht; M. Morikawa

2012-07-11T23:59:59.000Z

71

Probing spin frustration in high-symmetry magnetic nanomolecules by inelastic neutron scattering  

Science Journals Connector (OSTI)

Low temperature inelastic neutron scattering studies have been performed to characterize the low energy magnetic excitation spectrum of the magnetic nanomolecule {Mo72Fe30}. This unique highly symmetric cluster features spin frustration and is one of the largest discrete magnetic molecules studied to date by inelastic neutron scattering. The 30s=5?2 FeIII ions, embedded in a spherical polyoxomolybdate molecule, occupy the vertices of an icosidodecahedron and are coupled via nearest-neighbor antiferromagnetic interactions. The overall energy scale of the excitation and the gross features of the temperature dependence of the observed neutron scattering are explained by a quantum model of the frustrated spin cluster. However, no satisfactory theoretical explanation is yet available for the observed magnetic field dependence.

V. O. Garlea; S. E. Nagler; J. L. Zarestky; C. Stassis; D. Vaknin; P. Kögerler; D. F. McMorrow; C. Niedermayer; D. A. Tennant; B. Lake; Y. Qiu; M. Exler; J. Schnack; M. Luban

2006-01-23T23:59:59.000Z

72

Spin-polarized energy-band structure, conduction-electron polarization, spin densities, and the neutron magnetic form factor of ferromagnetic gadolinium  

Science Journals Connector (OSTI)

Conduction-electron polarization, spin densities, and neutron magnetic scattering in ferromagnetic Gd metal were studied using the spin-polarized augmented-plane-wave (APW) method in a warped-muffin-tin-potential formulation. The spin-up and spin-down bands were found to be very similar in shape to the bands from a paramagnetic calculation, with the exchange splitting proportional to the amount of d character in the bands. It was also found that the conduction-electron spin density determined from the APW wave functions is of mostly d character. This dominance of the d-like wave functions for the spin-dependent interactions is explained by (i) the much greater overlap of the 4f states with the d-like wave functions as compared to the s-p wave functions; (ii) the nearly complete d character of the bands in the region of the Fermi surface. The magnetic form factor was calculated from the conduction-electron spin density and compared with the recent neutron magnetic - form - factor measurement of Moon, Koehler, Cable, and Child. The calculated spin density was found to have the same shape as the "diffuse" density derived by Moon et al. (including a negative but much smaller in magnitude spin density at the c site in the unit cell). After the inclusion of core - polarization effects we conclude that large nonspherical contributions with Y33-Y3-3, and Y40 angular dependence are needed to explain the experimental results.

B. N. Harmon and A. J. Freeman

1974-09-01T23:59:59.000Z

73

Magnetic excitations and anomalous spin-wave broadening in multiferroic FeV2O4  

SciTech Connect (OSTI)

We report on the different roles of two orbital-active Fe2+ at the A site and V3+ at the B site in the magnetic excitations and on the anomalous spin-wave broadening in FeV2O4. FeV2O4 exhibits three structural transitions and successive paramagnetic (PM)–collinear ferrimagnetic (CFI)–noncollinear ferrimagnetic (NCFI)/ferroelectric transitions. The high-temperature tetragonal/PM–orthorhombic/CFI transition is accompanied by the appearance of a large energy gap in the magnetic excitations due to strong spin-orbit-coupling-induced anisotropy at the Fe2+ site. While there is no measurable increase in the energy gap from the orbital ordering of V3+ at the orthorhombic/CFI–tetragonal/NCFI transition, anomalous spin-wave broadening is observed in the orthorhombic/CFI state due to V3+ spin fluctuations at the B site. The spin-wave broadening is also observed at the zone boundary without softening in the NCFI/ferroelectric phase, which is discussed in terms of magnon-phonon coupling. Our study also indicates that the Fe2+ spins without the frustration at the A site may not play an important role in inducing ferroelectricity in the tetragonal/NCFI phase of FeV2O4.

Zhang, Qiang [Ames Laboratory; Ramazanoglu, Mehmet [Ames Laboratory; Chi, Songxue [Oak Ridge National Laboratory; Liu, Yong [Ames Laboratory; Lograsso, Thomas A. [Ames Laboratory; Vaknin, David [Ames Laboratory

2014-06-01T23:59:59.000Z

74

Orbital-resolved spin model for thermal magnetization switching in rare-earth-based ferrimagnets  

Science Journals Connector (OSTI)

The switching of rare-earth-based ferrimagnets triggered by thermal excitation is investigated on the basis of an atomistic spin model beyond the rigid-spin approximation, distinguishing magnetic moments due to electrons in d and f orbitals of the rare earth. It is shown that after excitation of the conduction electrons a transient ferromagneticlike state follows from a dissipationless spin dynamics where energy and angular momentum are distributed between the two sublattices. The final relaxation can then lead to a new state with the magnetization switched with respect to the initial state. The time scale of the switching event is to a large extent determined by the exchange interaction between the two sublattices.

S. Wienholdt; D. Hinzke; K. Carva; P. M. Oppeneer; U. Nowak

2013-07-24T23:59:59.000Z

75

Nuclear Magnetic Resonance and Nuclear-Spin Dynamics in InP  

Science Journals Connector (OSTI)

Pulsed- and steady-state nuclear-magnetic-resonance measurements are reported for P31 in InP. Measurements on "solid echoes" permit identification of various contributions to the second moment of the resonance. The dominant P31-In115,113 contribution is found to be about a factor of 2 smaller than expected from dipole-dipole interactions alone. A proposed explanation is based on interference between pseudodipolar and dipolar interactions of similar magnitude but opposite sign. The time evolution of the P31 magnetization along the effective field in the rotating frame indicates the presence of a significant cross-relaxation effect involving the resonant spin-Zeeman reservoir and the nonresonant spin-spin reservoir.

M. Engelsberg and R. E. Norberg

1972-05-01T23:59:59.000Z

76

Magnetic structure and spin excitations in BaMn2Bi2  

SciTech Connect (OSTI)

We present a single crystal neutron scattering study of BaMn2Bi2, a recently synthesized material with the same ThCr2Si2-type 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 to be unchanged by the 100 K structural phase transition.

Calder, Stuart A [ORNL; Saparov, Bayrammurad I [ORNL; Niedziela, Jennifer L [ORNL; Lumsden, Mark D [ORNL; Safa-Sefat, Athena [ORNL; Christianson, Andrew D [ORNL

2014-01-01T23:59:59.000Z

77

Magnetic order of the iron spins in NdFeAsO  

SciTech Connect (OSTI)

Polanzed and unpolarized neutron-diffraction mcasurements have bcr.:n carncd OUI to investigate the iron magnetIC order in undoped NdFeAsO. Antiferromagnctic order is observed bela" 141(6) K. which is in close proXtrlllty to the structural dlslonlon observed in thiS malena\\. The magnetl<: structure consists of chains of parallel spins that arc arrant;ed antiparallel between chams. which is Ihe same m-plane spin arrangement as observed in all the other iron oxypnictidc matcrials. Nearest-neighbor spins along the c a"is are antiparallellike LaFeAsO. The ordered momcnt is 0.25(7) /LR, which is the smallest moment found so far In these systems. 001: 10.1103/Ph}sRc"B.7S.064515 PACS numher(s): 74.25.Ha. 74.70.Dd. 75.25.+z. 75.40.Cx

Chen, Ying [National Institute of Standards and Technology (NIST); Lynn, J. W. [National Institute of Standards and Technology (NIST); Li, J. [National Institute of Standards and Technology (NIST); Li, G. [Beijing National Laboratroy for Condensed Matter Physics, Institute of Physics; Chen, G. F, [Beijing National Laboratroy for Condensed Matter Physics, Institute of Physics; Luo, J. L. [Chinese Academy of Sciences; Wang, N. L. [Chinese Academy of Sciences; Dai, Pengcheng [ORNL; de la Cruz, Clarina [University of Tennessee, Knoxville (UTK); Mook Jr, Herbert A [ORNL

2008-09-01T23:59:59.000Z

78

Spin-dependent phenomena in digital-magnetic heterostructures: Clustering and phase-space filling effects  

E-Print Network [OSTI]

appreciated in the context of Mn-based heterostructures. In digital-magnetic heterostructures DMH's Mn-1829 98 51848-6 Spin-related phenomena are most conveniently studied in Mn-based semiconductors the correct or- der of magnitude of the energy splittings as a function of B as in bulk Mn-based systems and

Wilkins, John

79

A novel neutron spin echo technique for measuring phonon linewidths using magnetic Wollaston prisms  

Science Journals Connector (OSTI)

A neutron spin echo spectrometer based on neutron magnetic Wollaston prisms is introduced to measure the linewidth of dispersive phonon excitations over the entire Brillouin zone with ?eV resolution. By tuning the instrument electromagnetically, the linewidths of phonon excitations with high energy and large group velocity can be measured.

Li, F.

2014-10-17T23:59:59.000Z

80

Magnetic resonance detection of individual proton spins using a quantum reporter network  

E-Print Network [OSTI]

We demonstrate a method of magnetic resonance imaging with single nuclear-spin sensitivity under ambient conditions. It employs a network of isolated electronic-spin quantum bits (qubits) that act as quantum reporters on the surface of high purity diamond. The reporter spins are localized with nanometer-scale uncertainty, and their quantum state is coherently manipulated and measured optically via a proximal nitrogen-vacancy (NV) color center located a few nanometers below the diamond surface. The quantum reporter network is then used for sensing, coherent coupling and imaging individual proton spins on the diamond surface with angstrom resolution. This approach may enable direct structural imaging of complex molecules that cannot be accessed from bulk studies. It realizes a new platform for probing novel materials, monitoring chemical reactions, and manipulation of complex systems on surfaces at a quantum level.

Alexander O. Sushkov; Igor Lovchinsky; Nicholas Chisholm; Ronald L. Walsworth; Hongkun Park; Mikhail D. Lukin

2014-10-14T23:59:59.000Z

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81

Nuclear spin conversion of water inside fullerene cages detected by low-temperature nuclear magnetic resonance  

SciTech Connect (OSTI)

The water-endofullerene H{sub 2}O@C{sub 60} provides a unique chemical system in which freely rotating water molecules are confined inside homogeneous and symmetrical carbon cages. The spin conversion between the ortho and para species of the endohedral H{sub 2}O was studied in the solid phase by low-temperature nuclear magnetic resonance. The experimental data are consistent with a second-order kinetics, indicating a bimolecular spin conversion process. Numerical simulations suggest the simultaneous presence of a spin diffusion process allowing neighbouring ortho and para molecules to exchange their angular momenta. Cross-polarization experiments found no evidence that the spin conversion of the endohedral H{sub 2}O molecules is catalysed by {sup 13}C nuclei present in the cages.

Mamone, Salvatore, E-mail: s.mamone@soton.ac.uk; Concistrè, Maria; Carignani, Elisa; Meier, Benno; Krachmalnicoff, Andrea; Johannessen, Ole G.; Denning, Mark; Carravetta, Marina; Whitby, Richard J.; Levitt, Malcolm H., E-mail: mhl@soton.ac.uk [School of Chemistry, University of Southampton, Southampton SO17 1BJ (United Kingdom); Lei, Xuegong; Li, Yongjun [Department of Chemistry, Columbia University, New York, New York 10027 (United States)] [Department of Chemistry, Columbia University, New York, New York 10027 (United States); Goh, Kelvin; Horsewill, Anthony J. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)] [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

2014-05-21T23:59:59.000Z

82

All-optical high-resolution magnetic resonance using a nitrogen-vacancy spin in diamond  

E-Print Network [OSTI]

We propose an all-optical scheme to prolong the quantum coherence of a negatively charged nitrogen-vacancy (NV) center in diamond. Optical control of the NV spin suppresses energy fluctuations of the $^{3}\\text{A}_{2}$ ground states and forms an energy gap protected subspace. By optical control, the spectral linewidth of magnetic resonance is much narrower and the measurement of the frequencies of magnetic field sources has higher resolution. The optical control also improves the sensitivity of the magnetic field detection and can provide measurement of the directions of signal sources.

Zhen-Yu Wang; Jian-Ming Cai; Alex Retzker; Martin B. Plenio

2014-04-04T23:59:59.000Z

83

Magnetization and spin diffusion of liquid {sup 3}He in aerogel  

SciTech Connect (OSTI)

We report theoretical calculations and experimental measurements of the normal-state spin diffusion coefficient of {sup 3}He in aerogel, including both elastic and inelastic scattering of {sup 3}He quasiparticles, and compare these results with data for {sup 3}He in 98% porous silica aerogel. This analysis provides a determination of the elastic mean free path within the aerogel. Measurements of the magnetization of the superfluid phase in the same aerogel samples provide a test of the theory of pairbreaking and magnetic response of low-energy excitations in the 'dirty' B phase of {sup 3}He in aerogel. A consistent interpretation of the data for the spin-diffusion coefficient, magnetization, and superfluid transition temperature is obtained by including correlation effects in the aerogel density.

Sauls, J. A. [Centre de Recherches sur les Tres Basses Temperatures, Centre National de la Recherche Scientifique, Laboratoire Associe a l'Universite J. Fourier, Boite Postale 166, 38042 Grenoble Cedex 9 (France); Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208 (United States); Bunkov, Yu.M.; Collin, E.; Godfrin, H. [Centre de Recherches sur les Tres Basses Temperatures, Centre National de la Recherche Scientifique, Laboratoire Associe a l'Universite J. Fourier, Boite Postale 166, 38042 Grenoble Cedex 9 (France); Sharma, P. [Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208 (United States)

2005-07-01T23:59:59.000Z

84

Behavior of nanoparticle clouds around a magnetized microsphere under magnetic and flow fields  

E-Print Network [OSTI]

When a micron-sized magnetizable particle is introduced into a suspension of nanosized magnetic particles, the nanoparticles accumulate around the microparticle and form thick anisotropic clouds extended in the direction of the applied magnetic field. This phenomenon promotes colloidal stabilization of bimodal magnetic suspensions and allows efficient magnetic separation of nanoparticles used in bioanalysis and water purification. In the present work, size and shape of nanoparticle clouds under the simultaneous action of an external uniform magnetic field and the flow have been studied in details. In experiments, dilute suspension of iron oxide nanoclusters (of a mean diameter of 60 nm) was pushed through a thin slit channel with the nickel microspheres (of a mean diameter of 50$\\mu$m) attached to the channel wall. The behavior of nanocluster clouds was observed in the steady state using an optical microscope. In the presence of strong enough flow, the size of the clouds monotonically decreases with increasing flow speed in both longitudinal and transverse magnetic fields. This is qualitatively explained by enhancement of hydrodynamic forces washing the nanoclusters away from the clouds. In the longitudinal field, the flow induces asymmetry of the front and the back clouds. To explain the flow and the field effects on the clouds, we have developed a simple model based on the balance of the stresses and particle fluxes on the cloud surface. This model, applied to the case of the magnetic field parallel to the flow, captures reasonably well the flow effect on the size and shape of the cloud and reveals that the only dimensionless parameter governing the cloud size is the ratio of hydrodynamic-to-magnetic forces - the Mason number. At strong magnetic interactions considered in the present work (dipolar coupling parameter $\\alpha \\geq 2$), the Brownian motion seems not to affect the cloud behavior.

Cécilia Magnet; Pavel Kuzhir; Georges Bossis; Alain Meunier; Sebastien Nave; Andrey Zubarev; Claire Lomenech; Victor Bashtovoi

2014-04-14T23:59:59.000Z

85

Generalized longitudinal susceptibility for magnetic monopoles in spin ice  

Science Journals Connector (OSTI)

...non-equilibrium physics of the Wien effect...is related to the rate of change of magnetization...and he derived the rate of entropy production...3) contains much physics and deserves subtle...0. Thus, as we pass from low to high...monopoles hopping at a rate nu 0 located near...

2012-01-01T23:59:59.000Z

86

Partial Spin Ordering and Complex Magnetic Structure in BaYFeO4: A Neutron Diffraction and High Temperature Susceptibility Study  

SciTech Connect (OSTI)

The novel iron-based compound, BaYFeO4, crystallizes in the Pnma space group with two distinct Fe3+ sites, that are alternately corner-shared [FeO5]7 square pyramids and [FeO6]9 octahedra, forming into [Fe4O18]24 rings, which propagate as columns along the b-axis. A recent report shows two discernible antiferromagnetic (AFM) transitions at 36 and 48 K in the susceptibility, yet heat capacity measurements reveal no magnetic phase transitions at these temperatures. An upturn in the magnetic susceptibility measurements up to 400 K suggests the presence of shortrange magnetic behavior at higher temperatures. In this Article, variable-temperature neutron powder diffraction and hightemperature magnetic susceptibility measurements were performed to clarify the magnetic behavior. Neutron powder diffraction confirmed that the two magnetic transitions observed at 36 and 48 K are due to long-range magnetic order. Below 48 K, the magnetic structure was determined as a spin-density wave (SDW) with a propagation vector, k = (0, 0, 1/3), and the moments along the b-axis, whereas the structure becomes an incommensurate cycloid [k = (0, 0, 0.35)] below 36 K with the moments within the bc-plane. However, for both cases the ordered moments on Fe3+ are only of the order 3.0 B, smaller than the expected values near 4.5 B, indicating that significant components of the Fe moments remain paramagnetic to the lowest temperature studied, 6 K. Moreover, new high-temperature magnetic susceptibility measurements revealed a peak maximum at 550 K indicative of short-range spin correlations. It is postulated that most of the magnetic entropy is thus removed at high temperatures which could explain the absence of heat capacity anomalies at the long-range ordering temperatures. Published spin dimer calculations, which appear to suggest a k = (0, 0, 0) magnetic structure, and allow for neither low dimensionality nor geometric frustration, are inadequate to explain the observed complex magnetic structure.

Thompson, Corey [Florida State University, Tallahassee] [Florida State University, Tallahassee; Greedan, John [McMaster University] [McMaster University; Garlea, Vasile O [ORNL] [ORNL; Flacau, Roxana [National Research Council of Canada] [National Research Council of Canada; Tan, Malinda [California State University, Long Beach (CSULB)] [California State University, Long Beach (CSULB); Derakhshan, Shahab [California State University, Long Beach (CSULB)] [California State University, Long Beach (CSULB)

2014-01-01T23:59:59.000Z

87

Spin and charge pumping in magnetic tunnel junctions with precessing magnetization: A nonequilibrium Green function approach  

E-Print Network [OSTI]

-dimensional model, consisting of a single precessing spin and a potential barrier as the "sample," and realistic generation" spintronic devices1 has largely been focused on harnessing coherent spin states electrical scheme is based on N1 F N2 multilayers11 where different voltages develop at different F Ni

Nikolic, Branislav K.

88

Calculation of the expectation values of the spin and the magnetic moment of the gamma photons created as a result of the electron-positron annihilation  

E-Print Network [OSTI]

We have calculated the expectation values of the spin and the intrinsic magnetic moment of the gamma photons created as a result of the electron-positron annihilation. We show that, depending on its helicity a gamma photon propagating in z direction with an angular frequency carries a magnetic moment of along the propagation direction. Here the (+) and (-) signs stand for the right hand and left circular helicity respectively. We also show that whatever the helicity is, the spin of each gamma photon is equal to zero (but not !). We argue that in a Stern-Gerlach experiment (SGE) the magnetic moment is an important property but not the spin of the particles. Because of these two symmetric values of the magnetic moment, we expect a splitting of the gamma photon beam into two symmetric subbeams in a (SGE). We believe that the present result will be helpful for understanding the recent attempts on the (SGE) with slow light and the behavior of the dark polaritons and also the atomic spinor polaritons.

Mesude Saglam; Ziya Saglam

2012-01-20T23:59:59.000Z

89

Effect of Electric and Magnetic Fields on Spin Dynamics in the Resonant Electric Dipole Moment Experiment  

E-Print Network [OSTI]

A buildup of the vertical polarization in the resonant electric dipole moment (EDM) experiment [Y. F. Orlov, W. M. Morse, and Y. K. Semertzidis, Phys. Rev. Lett. 96, 214802 (2006)] is affected by a horizontal electric field in the particle rest frame oscillating at a resonant frequency. This field is defined by the Lorentz transformation of an oscillating longitudinal electric field and a uniform vertical magnetic one. The effect of a longitudinal electric field is significant, while the contribution from a magnetic field caused by forced coherent longitudinal oscillations of particles is dominant. The effect of electric field on the spin dynamics was not taken into account in previous calculations. This effect is considerable and leads to decreasing the EDM effect for the deuteron and increasing it for the proton. The formula for resonance strengths in the EDM experiment has been derived. The spin dynamics has been calculated.

Alexander J. Silenko

2007-10-02T23:59:59.000Z

90

Probing Spin Liquids with a New Pulsed-Magnet System | Advanced Photon  

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

a Magnetic Moment in a Split Picosecond a Magnetic Moment in a Split Picosecond Unpeeling Atoms and Molecules from the Inside Out Butterfly Wing Yields Clues to Light-Altering Structures Squeezing Information from Materials under Extreme Pressure Quick-Change Molecules Caught in the Act Science Highlights Archives: 2013 | 2012 | 2011 | 2010 2009 | 2008 | 2007 | 2006 2005 | 2004 | 2003 | 2002 2001 | 2000 | 1998 | Subscribe to APS Science Highlights rss feed Probing Spin Liquids with a New Pulsed-Magnet System AUGUST 26, 2010 Bookmark and Share The (008) intensity color map on a θ vs. 2θ mesh. With increasing magnetic field the peak splits at a critical field of H ~29 T, which is a hallmark of a structural phase transition with a reduction from cubic to tetragonal or orthorhombic symmetry. Above the critical field,

91

Ultrafast Spin Avalanches in Crystals of Nanomagnets in Terms of Magnetic Detonation  

Science Journals Connector (OSTI)

Recent experiments [W. Decelle et al., Phys. Rev. Lett. 102, 027203 (2009)] have discovered ultrafast propagation of spin avalanches in crystals of nanomagnets, which is 3 orders of magnitude faster than the traditionally studied magnetic deflagration. The new regime has been hypothetically identified as magnetic detonation. Here we demonstrate unequivocally the possibility of magnetic detonation in the crystals, as a front consisting of a leading shock and a zone of Zeeman energy release. We study the key features of the process and find that the magnetic detonation speed only slightly exceeds the sound speed in agreement with the experimental observations. For combustion science, our results provide a unique physical example of extremely weak detonation.

M. Modestov; V. Bychkov; M. Marklund

2011-11-11T23:59:59.000Z

92

Thermal entanglement in a two-qubit Heisenberg XXZ spin chain under an inhomogeneous magnetic field  

E-Print Network [OSTI]

The thermal entanglement in a two-qubit Heisenberg \\emph{XXZ} spin chain is investigated under an inhomogeneous magnetic field \\emph{b}. We show that the ground-state entanglement is independent of the interaction of \\emph{z}-component $J_{z}$. The thermal entanglement at the fixed temperature can be enhanced when $J_{z}$ increases. We strictly show that for any temperature \\emph{T} and $J_{z}$ the entanglement is symmetric with respect to zero inhomogeneous magnetic field, and the critical inhomogeneous magnetic field $b_{c}$ is independent of $J_{z}$. The critical magnetic field $B_{c}$ increases with the increasing $|b|$ but the maximum entanglement value that the system can arrive becomes smaller.

Guo-Feng Zhang

2005-09-01T23:59:59.000Z

93

Comment on "Spin-glass attractor on tridimensional hierarchical lattices in the presence of an external magnetic field"  

E-Print Network [OSTI]

The effect of random or uniform magnetic fields on spin glasses on some d=3 hierarchical lattices has been studied, using renormalization-group theory, by Salmon and Nobre. In this work, the recursion relation for the ...

Berker, A. Nihat

94

Magnetic soft x-ray microscopy-imaging fast spin dynamics in magnetic nanostructures  

E-Print Network [OSTI]

fundamental time scale in magnetism is given by the time required to transfer energy and momentum from the electronic

Fischer, Peter; Kim, Dong-Hyun; Mesler, Brooke L.; Chao, Weilun; Sakdinawat, Anne E.; Anderson, Erik H.

2007-01-01T23:59:59.000Z

95

Dilute magnetism and spin-orbital percolation effects in Sr2Ir1?xRhxO4  

Science Journals Connector (OSTI)

We have used a combination of resonant magnetic x-ray scattering and x-ray absorption spectroscopy to investigate the properties of the doped spin-orbital Mott insulator Sr2Ir1?xRhxO4 (0.07?x?0.70). We show that Sr2Ir1?xRhxO4 represents a unique model system for the study of dilute magnetism in the presence of strong spin-orbit coupling, and provide evidence of a doping-induced change in magnetic structure and a suppression of magnetic order at xc?0.17. We demonstrate that Rh-doping introduces Rh3+/Ir5+ ions which effectively hole-dope this material. We propose that the magnetic phase diagram for this material can be understood in terms of a novel spin-orbital percolation picture.

J. P. Clancy; A. Lupascu; H. Gretarsson; Z. Islam; Y. F. Hu; D. Casa; C. S. Nelson; S. C. LaMarra; G. Cao; Young-June Kim

2014-02-10T23:59:59.000Z

96

Observations of thermally excited ferromagnetic resonance on spin torque oscillators having a perpendicularly magnetized free layer  

SciTech Connect (OSTI)

Measurements of thermally excited ferromagnetic resonance were performed on spin torque oscillators having a perpendicularly magnetized free layer and in-plane magnetized reference layer (abbreviated as PMF-STO in the following) for the purpose of obtaining magnetic properties in the PMF-STO structure. The measured spectra clearly showed a large main peak and multiple smaller peaks on the high frequency side. A Lorentzian fit on the main peak yielded Gilbert damping factor of 0.0041. The observed peaks moved in proportion to the out-of-plane bias field. From the slope of the main peak frequency as a function of the bias field, Lande g factor was estimated to be about 2.13. The mode intervals showed a clear dependence on the diameter of the PMF-STOs, i.e., intervals are larger for a smaller diameter. These results suggest that the observed peaks should correspond to eigenmodes of lateral spin wave resonance in the perpendicularly magnetized free layer.

Tamaru, S., E-mail: shingo.tamaru@aist.go.jp; Kubota, H.; Yakushiji, K.; Konoto, M.; Nozaki, T.; Fukushima, A.; Imamura, H.; Taniguchi, T.; Arai, H.; Tsunegi, S.; Yuasa, S. [Spintronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Suzuki, Y. [Spintronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan)

2014-05-07T23:59:59.000Z

97

arXiv:cond-mat/0007297v118Jul2000 Permanent magnetic moment in mesoscopic metals with spin-orbit interaction  

E-Print Network [OSTI]

arXiv:cond-mat/0007297v118Jul2000 Permanent magnetic moment in mesoscopic metals with spin-orbit interaction and odd number of electrons will have a permanent magnetic moment, even in zero magnetic field an effective single-electron Hamiltonian which accounts for spin-orbit coupling. I. INTRODUCTION Permanent

Serota, Rostislav

98

Identification and selection rules of the spin-wave eigen-modes in a normally magnetized nano-pillar  

E-Print Network [OSTI]

Identification and selection rules of the spin-wave eigen-modes in a normally magnetized nano nano-pillar (Permalloy-Copper-Permalloy) by means of a Magnetic Resonance Force Microscope (MRFM). We azimuthal index = 0, the RF cur- rent flowing through the nano-pillar, creating a circular RF Oersted field

99

Magnetic properties and critical behavior of Fe(tetracyanoethylene){sub 2}(centre dot)x(CH{sub 2}Cl{sub 2}): A high-T{sub c} molecule-based magnet  

SciTech Connect (OSTI)

We report magnetic studies of Fe(TCNE){sub 2}{center_dot}x(CH{sub 2}Cl{sub 2}), a member of the family of high-T{sub c} molecule-based magnets, M(TCNE){sub x}{center_dot}y(solvent) (M=V, Mn, TCNE=tetracyanoethelyne). Based on extensive static and dynamic magnetic measurements we show that this system has a complex magnetic behavior, with a mixture of ferrimagnetic and random anisotropy characteristics. The constricted hysteresis curve with a spin-flop shape, the ac susceptibility in the presence of a dc field, consistent with the spin-flop picture, and the remanent magnetization suggest ferrimagnetic behavior. The ac susceptibility data in zero dc field have modest frequency dependence suggesting glassiness, while the field-cooling/zero-field-cooling magnetization data show irreversibilities, starting at {approx}97 K, and increasing below {approx}20 K, all consistent with the behavior of reentrant random anisotropy magnets (RAM). Ferromagneticlike scaling analyses provide a critical temperature T{sub c}=97 K and the critical exponents {beta}=0.45 and {delta}=2.5, relatively consistent with random anisotropy magnet predictions. Also, the curvature of the Tmagnetic studies and analyzing the similarities with other members of this family of hybrid organic/inorganic compounds, we discuss the origins of anisotropy and randomness and the possible interconnections between ferrimagnetism and RAM (sperimagnetism) in Fe(TCNE){sub 2}{center_dot}x(CH{sub 2}Cl{sub 2}). (c) 2000 The American Physical Society.

Girtu, Mihai A. [Department of Physics, The Ohio State University, Columbus, Ohio 43210-1106 (United States); Wynn, Charles M. [Department of Physics, The Ohio State University, Columbus, Ohio 43210-1106 (United States); Zhang, Jie [Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850 (United States); Miller, Joel S. [Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850 (United States); Epstein, Arthur J. [Department of Physics and Department of Chemistry, The Ohio State University, Columbus, Ohio, 43210-1106 (United States)

2000-01-01T23:59:59.000Z

100

Long Time Behavior of Magnetic Field in Two Department of Mathematical Sciences, Montana State University  

E-Print Network [OSTI]

Long Time Behavior of Magnetic Field in Two Dimensions I.Klapper Department of Mathematical Sciences, Montana State University Bozeman, MT 59717 Abstract: As noted by Zel'dovich (1957), geometric constraints restrict the behavior of magnetic field in two dimensions. Here, tight long time bounds and decay

Klapper, Isaac

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Magnetism Highlights| Neutron Science | ORNL  

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

Magnetism Magnetism SHARE Magnetism Highlights 1-5 of 5 Results ARCS maps collaborative magnetic spin behavior in iron telluride December 01, 2011 - Researchers have long thought that magnetism and superconductivity are mutually exclusive. The former typically involves localized atomic electrons. The latter requires freely propagating, itinerant electrons. Unexpected Magnetic Excitations in Doped Insulator Surprise Researchers October 01, 2011 - When doping a disordered magnetic insulator material with atoms of a nonmagnetic material, the conventional wisdom is that the magnetic interactions between the magnetic ions in the material will be weakened. Neutron Analysis Reveals Unique Atomic-Scale Behavior of "Cobalt Blue" September 01, 2011 - Neutron scattering studies of "cobalt blue," a

102

HIGH RESOLUTION NMR IN INHOMOGENEOUS MAGNETIC FIELDS: APPLICATION OF TOTAL SPIN COHERENCE TRANSFER ECHOES  

E-Print Network [OSTI]

APPLICATION OF TOTAL SPIN COHERENCE TRANSFER ECHOES D.P.by total spin coherence transfer echo spectroscopy. (a) Thesequence to use total spin coherence transfer echoes to

Weitekamp, D.P.

2014-01-01T23:59:59.000Z

103

Spin Asymmetries Arising In Neutrino-Lepton Processes In A Magnetic Field And Their Macroscopic Appearance  

SciTech Connect (OSTI)

We present expressions that determine the differential cross sections and energy and momentum losses for the neutrino-lepton processes {nu}le- {yields} {nu}le-, {nu}-tildele- {yields} {nu}-tildele-, {nu}l{nu}-tildel {yields} e-e+, {nu}l{nu}-tildee {yields} l-e+, {nu}le- {yields} {nu}el- in a magnetic field with allowance for the longitudinal and transverse polarizations of the charged leptons and antileptons and the results on the spin asymmetries arising in these processes.

Huseynov, Vali A. [Department of General and Theoretical Physics, Nakhchivan State University, AZ 7000, Nakhchivan (Azerbaijan); Laboratory of Physical Research, Nakhchivan Division of Azerbaijan National Academy of Sciences, AZ 7000, Nakhchivan (Azerbaijan); Gasimova, Rasmiyya E.; Akbarova, Nurida Y.; Hajiyeva, Billura T. [Department of General and Theoretical Physics, Nakhchivan State University, AZ 7000, Nakhchivan (Azerbaijan)

2007-06-13T23:59:59.000Z

104

Tuning the magnetic and structural phase transitions of PrFeAsO via Fe/Ru spin dilution  

SciTech Connect (OSTI)

Neutron diffraction and muon spin relaxation measurements are used to obtain a detailed phase diagram of PrFe1{xRuxAsO. The isoelectronic substitution of Ru for Fe acts eectively as spin dilution, suppressing both the structural and magnetic phase transitions. The temperature, TS, of the tetragonal-orthorhombic structural phase transition decreases gradually as a function of x. Slightly below TS coherent precessions of the muon spin are observed corresponding to static magnetism, possibly re ecting a signicant magneto-elastic coupling in the FeAs layers. Short range order in both the Fe and Pr moments persists for higher levels of x. The static magnetic moments disappear at a concentration coincident with that expected for percolation of the J1 - J2 square lattice model.

Yiu, Yuen [ORNL; Bonfa, Pietro [University of Parma, Italy; Sanna, Samuele [Universita di Pavia, Italy; De Renzi, Roberto [University of Parma, Italy; Caretta, Pietro [Universita di Pavia, Italy; McGuire, Michael A [ORNL; Huq, Ashfia [ORNL; Nagler, Stephen E [ORNL

2014-01-01T23:59:59.000Z

105

A co-crystal of polyoxometalates exhibiting single-molecule magnet behavior: the structural origin of a large magnetic anisotropy  

SciTech Connect (OSTI)

A polyoxometalate-based {MnIII3MnIV} single-molecule magnet exhibits a large axial anisotropy (D = ?0.86 cm?1) resulting from a near-parallel alignment of Jahn–Teller axes. Its rigorous three-fold symmetry (i.e. rhombicity E ? 0) and increased intercluster separation via co-crystallization effectively hamper quantum tunnelling of the magnetization. Graphical abstract: A co-crystal of polyoxometalates exhibiting single-molecule magnet behavior: the structural origin of a large magnetic anisotropy

Fang, Xikui; McCallum, Kendall; Pratt III, Harry D.; Anderson, Travis M.; Dennis, Kevin; Luban, Marshall

2012-03-29T23:59:59.000Z

106

Spin dynamics in a spin-correlated radical pair of photosystem I. Pulsed time-resolved EPR at high magnetic field.  

SciTech Connect (OSTI)

Spin-dynamics of the spin-correlated radical pair (SCRP) P{sub 700}{sup +}A{sub 1A}{sup -} in the photosystem I (PSI) reaction center protein have been investigated with high-frequency (HF), time-resolved EPR spectroscopy. The superior spectral resolution of HF EPR enables spin-dynamics for both the donor and acceptor radicals in the pair to be monitored independently. Decay constants of each spin were measured as a function of temperature and compared to data obtained at X-band EPR. Relaxation times, T{sub 1}, and decay rates, k{sub S}, are the same at both X- and D-band magnetic fields. The spin-dynamics within the radical pair were determined from theoretical simulation of experimental time-resolved HF EPR spectra. At low temperatures, T < 60 K, the decay of the SCRP from the singlet state, k{sub S}, is the predominant process, while at high temperatures, T > 130 K, the T{sub 1} relaxation is much faster than k{sub S}. The recombination rate k{sub S} was observed to decrease as the temperature is increased. These EPR spectral results are in agreement with previously reported optical measurements of P{sub 700}{sup +}A{sub 1}{sup -} radical pair recombination.

Poluektov, O. G.; Paschenko, S. V.; Utschig, L. M.; Chemical Sciences and Engineering Division

2009-01-01T23:59:59.000Z

107

Magnons and continua in a magnetized and dimerized spin-1/2 chain  

SciTech Connect (OSTI)

We examine the magnetic field dependent excitations of the dimerized spin-1/2 chain, copper nitrate, with antiferromagnetic intra-dimer exchange $J_1=0.44$ meV and exchange alternation $\\alpha=J_2/J_1=0.24$. Magnetic excitations in three distinct regimes of magnetization are probed through inelastic neutron scattering at low temperatures. At low and high fields there are three and two long-lived magnon-like modes, respectively. The number of modes and the anti-phase relationship between the wave-vector dependent energy and intensity of magnon scattering reflect the distinct ground states: A singlet ground state at low fields $\\mu_0H < \\mu_0H_{c1} = 2.8$~T and an $S_z=1/2$ product state at high fields $\\mu_0H > \\mu_0H_{c2} = 4.2$~T. In the intermediate field regime, a continuum of scattering for $\\hbar\\omega\\approx J_1$ is indicative of a strongly correlated gapless quantum state without coherent magnons.

Stone, Matthew B [ORNL; Chen, Y. [National Institute of Standards and Technology (NIST); Broholm, C. [Johns Hopkins University; Reich, D. H. [Johns Hopkins University; Xu, Guangyong [Brookhaven National Laboratory (BNL); Copley, John R. D. [National Institute of Standards and Technology (NIST), Gaithersburg, MD; Cook, Jeremy [National Institute of Standards and Technology (NIST)

2014-01-01T23:59:59.000Z

108

Low Energy Spin Waves and Magnetic Interactions in SrFe{sub 2}As{sub 2}  

SciTech Connect (OSTI)

We report inelastic neutron scattering studies of magnetic excitations in antiferromagnetically ordered SrFe{sub 2}As{sub 2} (T{sub N}=200-220 K), the parent compound of the FeAs-based superconductors. At low temperatures (T=7 K), the magnetic spectrum S(Q,({Dirac_h}/2{pi}){omega}) consists of a Bragg peak at the elastic position (({Dirac_h}/2{pi}){omega}=0 meV), a spin gap ({delta}{<=}6.5 meV), and sharp spin-wave excitations at higher energies. Based on the observed dispersion relation, we estimate the effective magnetic exchange coupling using a Heisenberg model. On warming across T{sub N}, the low-temperature spin gap rapidly closes, with weak critical scattering and spin-spin correlations in the paramagnetic state. The antiferromagnetic order in SrFe{sub 2}As{sub 2} is therefore consistent with a first order phase transition, similar to the structural lattice distortion.

Zhao Jun; Li Shiliang [Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200 (United States); Yao Daoxin; Carlson, E. W.; Hu Jiangping [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Hong Tao; Mook, H. A. [Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393 (United States); Chen, Y.; Chang, S.; Ratcliff, W. II; Lynn, J. W. [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102 (United States); Chen, G. F.; Luo, J. L.; Wang, N. L. [Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China); Dai Pengcheng [Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996-1200 (United States); Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393 (United States)

2008-10-17T23:59:59.000Z

109

Field-Induced Freezing of a Quantum Spin Liquid on the Kagome Lattice P. Mendels,1  

E-Print Network [OSTI]

a gapless spin-liquid behavior in zero field, we uncover an instability toward a spin-solid phase at sub with dense sets of low energy excitations in all spin sectors [5,6]. A recent state-of-the-art calculation [7 planes which ensure the quasi-two-dimensionality of the magnetic net (Fig. 1). Despite a sizable

Paris-Sud 11, Université de

110

Crystallization Behavior, Nanostructure and Magnetic Properties of Melt-spun (Nd,Pr,Dy)2(Fe,Co,Mo)14B/-Fe Nanocomposite Magnets  

E-Print Network [OSTI]

behavior, phase evolution, nanostructure, exchange coupling and hard magnetic properties of melt-spun Nd2 extensive attention for the development of novel permanent magnets with high magnetic performance [1, exchange coupling and magnetic properties of the nanocomposites. In the present work, the crystallization

Garmestani, Hamid

111

ELSEWER Journal of Magnetism and Magnetic Materials 169 (1997) 261-270 Superparamagnetic behavior of Fe,GaAs precipitates in GaAs  

E-Print Network [OSTI]

ELSEWER Journal of Magnetism and Magnetic Materials 169 (1997) 261-270 Superparamagnetic behavior; revised 6 December 1996 Abstract We present magnetization measurements on Fe3GaAs clusters distributed-dependent magnetization well above the blocking temperature indicate a particle size distribution in agreement

Woodall, Jerry M.

112

Spin-dependence of the electron scattering cross section by a magnetic layer system and the magneto-resistance  

SciTech Connect (OSTI)

The authors present a theoretical model for calculating the spin-dependent cross section of the scattering of electrons by a magnetic layer system. The model demonstrates that the cross sections of the scattering are different for spin up and spin down electrons. The model assumes that the electrical resistivity in a conductor is proportional to the scattering cross section of the electron in it. It is believed to support the two channel mechanism in interpreting magneto-resistance (MR). Based on the model without considering the scattering due to the interfacial roughness and the spin flipping scattering, the authors have established a relationship between MR and the square of the magnetic moment in the bulk sample without considering the scattering due to the interfacial roughness and the spin flipping scattering. It can also qualitatively explain the MR difference between the current in plane (CIP) and current perpendicular to the plane (CPP) configurations. The predictions by the model agree well with the experimental findings.

Wang, J.T.; Tang, F.; Brown, W.D.; Bagayoko, D. (Southern Univ. and A and M College, Baton Rouge, LA (United States). Physics Dept.)

1998-12-20T23:59:59.000Z

113

Magnetic orders and spin-flop transitions in the cobalt doped multiferroic $\\rm Mn_{1-x}Co_{x}WO_4$  

SciTech Connect (OSTI)

We present a comprehensive single crystal neutron diffraction investigation of the $\\rm Mn_{1-x}Co_{x}WO_4$ with $0.02\\leq x \\leq0.30$. At lower concentration $x \\leq 0.05$, the system is quickly driven into the multiferroic phase with spin structure forming an elliptical spiral order similar to the parent compound. The reduction of electric polarization is ascribed to the tilting of the spiral plane. For $x\\sim 0.075$, the magnetic structure undergoes a spin flop transition that is characterized by a sudden rotation of the spin helix envelope into the $ac$ plane. This spin structure persists for concentration up to $x=0.15$, where additional competing magnetic orders appear at low temperature. For $0.17 \\leq x \\leq 0.30$, the system experiences another spin flop transition and recovers the low-$x$ spiral spin configuration. A simple commensurate spin structure with $\\vec{q}=(0.5,0,0)$ is found to coexist with the incommensurate spiral order. The complex evolution of magnetic structure in Co doped $\\rm MnWO_4$ contrasts sharply with other transition metal ion doped $\\rm Mn_{1-x}A_xWO_4$ (A=Zn, Mg, Fe) where the chemical substitutions stabilize only one type of magnetic structure. The rich phase diagram of $\\rm Mn_{1-x}Co_{x}WO_4 $ results from the interplay between magnetic frustration and spin anisotropy of the Co ions.

Chi, Songxue [ORNL; Fernandez-Baca, Jaime A [ORNL; Cao, Huibo [ORNL; Liang, K. C. [University of Houston, Houston; Wang, Y. Q. [University of Houston, Houston; Lorenz, Bernd [University of Houston, Houston; Chu, C. W. [University of Houston, Houston

2012-01-01T23:59:59.000Z

114

Current-induced switching of magnetic tunnel junctions: Effects of field-like spin-transfer torque, pinned-layer magnetization orientation, and temperature  

SciTech Connect (OSTI)

We study current-induced switching in magnetic tunnel junctions in the presence of a field-like spin-transfer torque and titled pinned-layer magnetization in the high current limit at finite temperature. We consider both the Slonczewski and field-like torques with coefficients a{sub J} and b{sub J}, respectively. At finite temperatures, ?=b{sub J}/a{sub J}=±1 leads to a smaller mean switching time compared that with ?=0. The reduction of switching time in the presence of the field-like term is due to the alignment effect (for ?>0) and the initial torque effect.

Tiwari, R. K.; Jhon, M. H.; Ng, N.; Gan, C. K., E-mail: ganck@ihpc.a-star.edu.sg [Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, 16-16 Connexis, Singapore 138632 (Singapore); Srolovitz, D. J. [Department of Materials Science, Engineering, Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

2014-01-13T23:59:59.000Z

115

Co-Doped (La,Sr)TiO3-?: A High Curie Temperature Diluted Magnetic System with Large Spin Polarization  

Science Journals Connector (OSTI)

We report on tunneling magnetoresistance (TMR) experiments that demonstrate the existence of a significant spin polarization in Co-doped (La,Sr)TiO3-? (Co-LSTO), a ferromagnetic diluted magnetic oxide system (DMOS) with high Curie temperature. These TMR experiments have been performed on magnetic tunnel junctions associating Co-LSTO and Co electrodes. Extensive structural analysis of Co-LSTO combining high-resolution transmission electron microscopy and Auger electron spectroscopy excluded the presence of Co clusters in the Co-LSTO layer and thus, the measured ferromagnetism and high spin polarization are intrinsic properties of this DMOS. Our results argue for the DMOS approach with complex oxide materials in spintronics.

G. Herranz, R. Ranchal, M. Bibes, H. Jaffrès, E. Jacquet, J.-L. Maurice, K. Bouzehouane, F. Wyczisk, E. Tafra, M. Basletic, A. Hamzic, C. Colliex, J.-P. Contour, A. Barthélémy, and A. Fert

2006-01-19T23:59:59.000Z

116

Spin oscillations of relativistic fermions in the field of a traveling circularly polarized electromagnetic wave and a constant magnetic field  

E-Print Network [OSTI]

The Dirac equation, in the field of a traveling circularly polarized electromagnetic wave and a constant magnetic field, has singular solutions, corresponding the expansion of energy in vicinity of some singular point. These solutions described relativistic fermions. States relating to these solutions are not stationary. The temporal change of average energy, momentum and spin for single and mixed states is studied in the paper. A distinctive feature of the states is the disappearance of the longitudinal component of the average spin. Another feature is the equivalence of the condition of fermion minimal energy and the classical condition of the magnetic resonance. Finding such solutions assumes the use of a transformation for rotating and co-moving frames of references. Comparison studies of solutions obtained with the Galilean and non-Galilean transformation shown that some parameters of the non-Galilean transformation may be measured in high-energy physics.

Boris V. Gisin

2014-05-13T23:59:59.000Z

117

Enhanced synchronization in an array of spin torque nano oscillators in the presence of oscillating external magnetic field  

E-Print Network [OSTI]

We demonstrate that the synchronization of an array of electrically coupled spin torque nano-oscillators (STNO) modelled by Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation can be enhanced appreciably in the presence of a common external microwave magnetic field. The applied microwave magnetic field stabilizes and enhances the regions of synchronization in the parameter space of our analysis, where the oscillators are exhibiting synchronized oscillations thereby emitting improved microwave power. To characterize the synchronized oscillations we have calculated the locking range in the domain of external source frequency.

B. Subash; V. K. Chandrasekar; M. Lakshmanan

2014-09-15T23:59:59.000Z

118

Enhanced synchronization in an array of spin torque nano oscillators in the presence of oscillating external magnetic field  

E-Print Network [OSTI]

We demonstrate that the synchronization of an array of electrically coupled spin torque nano-oscillators (STNO) modelled by Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation can be enhanced appreciably in the presence of a common external microwave magnetic field. The applied microwave magnetic field stabilizes and enhances the regions of synchronization in the parameter space of our analysis, where the oscillators are exhibiting synchronized oscillations thereby emitting improved microwave power. To characterize the synchronized oscillations we have calculated the locking range in the domain of external source frequency.

B. Subash; V. K. Chandrasekar; M. Lakshmanan

2014-12-23T23:59:59.000Z

119

Magnetism and superconductivity in quark matter  

E-Print Network [OSTI]

Magnetic properties of quark matter and its relation to the microscopic origin of the magnetic field observed in compact stars are studied. Spontaneous spin polarization appears in high-density region due to the Fock exchange term, which may provide a scenario for the behaviors of magnetars. On the other hand, quark matter becomes unstable to form spin density wave in the moderate density region, where restoration of chiral symmetry plays an important role. Coexistence of magnetism and color superconductivity is also discussed.

T. Tatsumi; E. Nakano; K. Nawa

2005-06-01T23:59:59.000Z

120

Nuclear Spin Lattice Relaxation and Conductivity Studies of the Non-Arrhenius Conductivity Behavior in Lithium Fast Ion Conducting Sulfide Glasses  

SciTech Connect (OSTI)

As time progresses, the world is using up more of the planet's natural resources. Without technological advances, the day will eventually arrive when these natural resources will no longer be sufficient to supply all of the energy needs. As a result, society is seeing a push for the development of alternative fuel sources such as wind power, solar power, fuel cells, and etc. These pursuits are even occurring in the state of Iowa with increasing social pressure to incorporate larger percentages of ethanol in gasoline. Consumers are increasingly demanding that energy sources be more powerful, more durable, and, ultimately, more cost efficient. Fast Ionic Conducting (FIC) glasses are a material that offers great potential for the development of new batteries and/or fuel cells to help inspire the energy density of battery power supplies. This dissertation probes the mechanisms by which ions conduct in these glasses. A variety of different experimental techniques give a better understanding of the interesting materials science taking place within these systems. This dissertation discusses Nuclear Magnetic Resonance (NMR) techniques performed on FIC glasses over the past few years. These NMR results have been complimented with other measurement techniques, primarily impedance spectroscopy, to develop models that describe the mechanisms by which ionic conduction takes place and the dependence of the ion dynamics on the local structure of the glass. The aim of these measurements was to probe the cause of a non-Arrhenius behavior of the conductivity which has been seen at high temperatures in the silver thio-borosilicate glasses. One aspect that will be addressed is if this behavior is unique to silver containing fast ion conducting glasses. more specifically, this study will determine if a non-Arrhenius correlation time, {tau}, can be observed in the Nuclear Spin Lattice Relaxation (NSLR) measurements. If so, then can this behavior be modeled with a new single distribution of activation energies (DAE) to calculate the corresponding conductivity and relaxation rates as a function of temperature and frequency?

Benjamin Michael Meyer

2003-05-31T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic  

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

Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic Vortices Print Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic Vortices Print Soft magnetic, micron-sized thin-film structures with magnetic vortices are intriguing systems that may one day be used in ultrafast computer memories. In such systems, the otherwise in-plane magnetization turns perpendicular to the plane at the center of the vortex, forming the vortex core. Because such a core has two possible polarizations (up or down) and can be switched between these two states by a small alternating magnetic field, it could serve as a memory bit in future magnetic memory devices. However, these magnetic structures often contain numerous imperfections such as domain wall pinning sites, which have to be taken into account for the practical application of such systems. To study how these defects affect the dynamics of magnetic vortices, researchers from Belgium, Germany, and the United States investigated square-shaped and disk-shaped thin-film structures with artificially introduced imperfections in the form of nanometer-sized holes. They used time-resolved scanning transmission x-ray microscopy (STXM) at ALS Beamline 11.0.2 to determine the frequency at which these vortices vibrate (their eigenfrequency). The imperfections were found to cause a higher vibrational frequency in square-shaped structures, but did not influence the disk-shaped structures. Knowledge of the frequency is crucial for vortex-based memories, since the electric signal for writing data needs to be precisely tuned to it.

122

Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic  

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

Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic Vortices Print Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic Vortices Print Soft magnetic, micron-sized thin-film structures with magnetic vortices are intriguing systems that may one day be used in ultrafast computer memories. In such systems, the otherwise in-plane magnetization turns perpendicular to the plane at the center of the vortex, forming the vortex core. Because such a core has two possible polarizations (up or down) and can be switched between these two states by a small alternating magnetic field, it could serve as a memory bit in future magnetic memory devices. However, these magnetic structures often contain numerous imperfections such as domain wall pinning sites, which have to be taken into account for the practical application of such systems. To study how these defects affect the dynamics of magnetic vortices, researchers from Belgium, Germany, and the United States investigated square-shaped and disk-shaped thin-film structures with artificially introduced imperfections in the form of nanometer-sized holes. They used time-resolved scanning transmission x-ray microscopy (STXM) at ALS Beamline 11.0.2 to determine the frequency at which these vortices vibrate (their eigenfrequency). The imperfections were found to cause a higher vibrational frequency in square-shaped structures, but did not influence the disk-shaped structures. Knowledge of the frequency is crucial for vortex-based memories, since the electric signal for writing data needs to be precisely tuned to it.

123

Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic  

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

Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic Vortices Print Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic Vortices Print Soft magnetic, micron-sized thin-film structures with magnetic vortices are intriguing systems that may one day be used in ultrafast computer memories. In such systems, the otherwise in-plane magnetization turns perpendicular to the plane at the center of the vortex, forming the vortex core. Because such a core has two possible polarizations (up or down) and can be switched between these two states by a small alternating magnetic field, it could serve as a memory bit in future magnetic memory devices. However, these magnetic structures often contain numerous imperfections such as domain wall pinning sites, which have to be taken into account for the practical application of such systems. To study how these defects affect the dynamics of magnetic vortices, researchers from Belgium, Germany, and the United States investigated square-shaped and disk-shaped thin-film structures with artificially introduced imperfections in the form of nanometer-sized holes. They used time-resolved scanning transmission x-ray microscopy (STXM) at ALS Beamline 11.0.2 to determine the frequency at which these vortices vibrate (their eigenfrequency). The imperfections were found to cause a higher vibrational frequency in square-shaped structures, but did not influence the disk-shaped structures. Knowledge of the frequency is crucial for vortex-based memories, since the electric signal for writing data needs to be precisely tuned to it.

124

Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic  

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

Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic Vortices Print Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic Vortices Print Soft magnetic, micron-sized thin-film structures with magnetic vortices are intriguing systems that may one day be used in ultrafast computer memories. In such systems, the otherwise in-plane magnetization turns perpendicular to the plane at the center of the vortex, forming the vortex core. Because such a core has two possible polarizations (up or down) and can be switched between these two states by a small alternating magnetic field, it could serve as a memory bit in future magnetic memory devices. However, these magnetic structures often contain numerous imperfections such as domain wall pinning sites, which have to be taken into account for the practical application of such systems. To study how these defects affect the dynamics of magnetic vortices, researchers from Belgium, Germany, and the United States investigated square-shaped and disk-shaped thin-film structures with artificially introduced imperfections in the form of nanometer-sized holes. They used time-resolved scanning transmission x-ray microscopy (STXM) at ALS Beamline 11.0.2 to determine the frequency at which these vortices vibrate (their eigenfrequency). The imperfections were found to cause a higher vibrational frequency in square-shaped structures, but did not influence the disk-shaped structures. Knowledge of the frequency is crucial for vortex-based memories, since the electric signal for writing data needs to be precisely tuned to it.

125

Occluded cobalt species over ZSM-5 matrix: Design, preparation, characterization and magnetic behavior  

SciTech Connect (OSTI)

Co-containing molecular sieves with MFI structure was synthesized by the hydrothermal crystallization method and cobalt was incorporated in it by wet impregnation at different percentages. Thermal post-treatments were applied to Co-ZSM-5: calcination and reduction. X ray diffraction (XRD) and FTIR studies confirmed crystallinity, structure and orthorhombic symmetry of the obtained samples (Co-ZSM-5 calcined and Co-ZSM-5 reduced). The XRD, Raman spectroscopy, SEM and TPR techniques for the calcined samples showed the presence of Co{sub 3}O{sub 4} which diminished in the reduced samples and Co{sup 0} appeared. The magnetic behavior of the materials was evaluated by magnetization (M) variation with applied magnetic field (H) at different temperatures. Low magnetization is observed in the calcined samples while high values are attained in the reduced samples, due to the presence of metallic Co.

Pierella, Liliana B. [Grupo Zeolitas-CITeQ, Centro de Investigacion y Tecnologia Quimica, Facultad Cordoba, Universidad Tecnologica Nacional, Cordoba (Argentina); Conicet, Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina)], E-mail: lpierella@scdt.frc.utn.edu.ar; Saux, Clara [Grupo Zeolitas-CITeQ, Centro de Investigacion y Tecnologia Quimica, Facultad Cordoba, Universidad Tecnologica Nacional, Cordoba (Argentina); Conicet, Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina); Bertorello, Hector R.; Bercoff, Paula G. [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Cordoba (Argentina); Conicet, Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina); Botta, Pablo M.; Rivas, J. [Departamento de Fisica Aplicada, Universidad de Santiago de Compostela, Facultad de Fisica, Campus Sur, 15782 Santiago de Compostela (Spain)

2008-08-04T23:59:59.000Z

126

Temperature-dependent magnetic Compton scattering study of spin moments in Ce(Fe0.94Ru0.06)2  

Science Journals Connector (OSTI)

We report on the study of spin moments in Ce(Fe0.94Ru0.06)2 using magnetic Compton scattering. The measurements on polycrystalline sample were carried out at SPring-8, Japan with 175 keV elliptically polarized synchrotron radiation at 70, 90, 120, 150, and 190 K in 2 T field. The temperature variation of the magnetic effect exhibits clearly the double magnetic transition, i.e., from antiferromagnetic to ferromagnetic and ferromagnetic to paramagnetic transition in agreement with the resistivity and magnetization studies on this material. A comparison of temperature-dependent spin moments in the present sample with Ce(Fe0.96Ru0.04)2 shows interesting features of spin momentum density.

B. K. Sharma; V. Purvia; B. L. Ahuja; M. Sharma; P. Chaddah; S. B. Roy; Y. Kakutani; A. Koizumi; T. Nagao; A. Omura; T. Kawai; N. Sakai

2005-10-10T23:59:59.000Z

127

Unraveling multi-spin effects in rotational resonance nuclear magnetic resonance using effective reduced density matrix theory  

SciTech Connect (OSTI)

A quantum-mechanical model integrating the concepts of reduced density matrix and effective Hamiltonians is proposed to explain the multi-spin effects observed in rotational resonance (R{sup 2}) nuclear magnetic resonance (NMR) experiments. Employing this approach, the spin system of interest is described in a reduced subspace inclusive of its coupling to the surroundings. Through suitable model systems, the utility of our theory is demonstrated and verified with simulations emerging from both analytic and numerical methods. The analytic results presented in this article provide an accurate description/interpretation of R{sup 2} experimental results and could serve as a test-bed for distinguishing coherent/incoherent effects in solid-state NMR.

SivaRanjan, Uppala; Ramachandran, Ramesh, E-mail: rramesh@iisermohali.ac.in [Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Manauli, P.O. Box-140306, Mohali, Punjab (India)] [Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Manauli, P.O. Box-140306, Mohali, Punjab (India)

2014-02-07T23:59:59.000Z

128

Far-Infrared Studies of Spin-Peierls Materials in a Magnetic Field  

Science Journals Connector (OSTI)

Both a 20 T superconducting magnet and a 33 T resistive magnet were employed for the magnetic field work. ... Bottom panel:? dashed line, absolute transmission spectra of MEM(TCNQ)2 at 300 K and zero field; solid lines, 5 K transmission ratios of MEM(TCNQ)2 taken as a function of applied magnetic field. ... (47)?Ng, H. K.; Wang, Y. J. Proceedings of the Physical Phenomena at High Magnetic Fields II Conference, Tallahassee, FL, Fisk, Z., Ed.; 1995. ...

G. Li; J. S. Lee; V. C. Long; J. L. Musfeldt; Y. J. Wang; M. Almeida; A. Revcolevschi; G. Dhalenne

1998-03-04T23:59:59.000Z

129

Effects of spin on the dynamics of the 2D Dirac oscillator in the magnetic cosmic string background  

E-Print Network [OSTI]

In this work the dynamics of a 2D Dirac oscillator in the spacetime of a magnetic cosmic string is considered. It is shown that earlier approaches to this problem have neglected a $\\delta$ function contribution to the full Hamiltonian, which comes from the Zeeman interaction. The inclusion of spin effects leads to results which confirm a modified dynamics. Based on the self-adjoint extension method, we determined the most relevant physical quantities, such as energy spectrum, wave functions and the self-adjoint extension parameter by applying boundary conditions allowed by the system.

Fabiano M. Andrade; Edilberto O. Silva

2014-03-17T23:59:59.000Z

130

Effects of spin on the dynamics of the 2D Dirac oscillator in the magnetic cosmic string background  

E-Print Network [OSTI]

In this work the dynamics of a 2D Dirac oscillator in the spacetime of a magnetic cosmic string is considered. It is shown that earlier approaches to this problem have neglected a $\\delta$ function contribution to the full Hamiltonian, which comes from the Zeeman interaction. The inclusion of spin effects leads to results which confirm a modified dynamics. Based on the self-adjoint extension method, we determined the most relevant physical quantities, such as energy spectrum, wave functions and the self-adjoint extension parameter by applying boundary conditions allowed by the system.

Andrade, Fabiano M

2014-01-01T23:59:59.000Z

131

Dynamics of quantum spin liquid and spin solid phases in IPA-CuCl3 under an applied magnetic field studied with neutron scattering  

SciTech Connect (OSTI)

Inelastic and elastic neutron scattering is used to study spin correlations in the quasi-one-dimensional quantum antiferromagnet IPA-CuCl3 in strong applied magnetic fields. A condensation of magnons and commensurate transverse long-range ordering is observe at a critical field Hc=9.5 T. The field dependencies of the energies and polarizations of all magnon branches are investigated both below and above the transition point. Their dispersion is measured across the entire one-dimensional Brillouin zone in magnetic fields up to 14 T. The critical wave vector of magnon spectrum truncation Masuda et al., Phys. Rev. Lett. 96, 047210 2006 is found to shift from hc0,35 at HHC to hc=0.25 for HHC. A drastic reduction of magnon bandwidths in the ordered phase Garlea et al., Phys. Rev. Lett. 98, 167202 2007 is observed and studied in detail. New features of the spectrum, presumably related to this bandwidth collapse, are observed just above the transition field.

Zheludev, Andrey I [ORNL; Garlea, Vasile O [ORNL; Masuda, T. [Yokohama City University, Japan; Manaka, H. [Kagoshima University, Kagoshima JAPAN; Regnault, L.-P. [CEA, Grenoble, France; Ressouche, E. [CEA, Grenoble, France; Grenier, B. [CEA, Grenoble, France; Chung, J.-H. [National Institute of Standards and Technology (NIST); Qiu, Y. [National Institute of Standards and Technology (NIST); Habicht, Klaus [Hahn-Meitner Institut, Berlin, Germany; Kiefer, K. [Hahn-Meitner Institut, Berlin, Germany; Boehm, Martin [Institut Laue-Langevin (ILL)

2007-01-01T23:59:59.000Z

132

Theoretical prediction of nuclear magnetic shieldings and indirect spin-spin coupling constants in 1,1-, cis-, and trans-1,2-difluoroethylenes  

SciTech Connect (OSTI)

A theoretical prediction of nuclear magnetic shieldings and indirect spin-spin coupling constants in 1,1-, cis- and trans-1,2-difluoroethylenes is reported. The results obtained using density functional theory (DFT) combined with large basis sets and gauge-independent atomic orbital calculations were critically compared with experiment and conventional, higher level correlated electronic structure methods. Accurate structural, vibrational, and NMR parameters of difluoroethylenes were obtained using several density functionals combined with dedicated basis sets. B3LYP/6-311++G(3df,2pd) optimized structures of difluoroethylenes closely reproduced experimental geometries and earlier reported benchmark coupled cluster results, while BLYP/6-311++G(3df,2pd) produced accurate harmonic vibrational frequencies. The most accurate vibrations were obtained using B3LYP/6-311++G(3df,2pd) with correction for anharmonicity. Becke half and half (BHandH) density functional predicted more accurate {sup 19}F isotropic shieldings and van Voorhis and Scuseria's ?-dependent gradient-corrected correlation functional yielded better carbon shieldings than B3LYP. A surprisingly good performance of Hartree-Fock (HF) method in predicting nuclear shieldings in these molecules was observed. Inclusion of zero-point vibrational correction markedly improved agreement with experiment for nuclear shieldings calculated by HF, MP2, CCSD, and CCSD(T) methods but worsened the DFT results. The threefold improvement in accuracy when predicting {sup 2}J(FF) in 1,1-difluoroethylene for BHandH density functional compared to B3LYP was observed (the deviations from experiment were ?46 vs. ?115 Hz)

Nozirov, Farhod, E-mail: teobaldk@gmail.com, E-mail: farhod.nozirov@gmail.com [Department of Physics, 4513 Manhattan College Parkway Riverdale, New York 10471 (United States)] [Department of Physics, 4513 Manhattan College Parkway Riverdale, New York 10471 (United States); Stachów, Micha?, E-mail: michal.stachow@gmail.com [Faculty of Chemistry, Opole University, 48, Oleska Street, 45-052 Opole (Poland)] [Faculty of Chemistry, Opole University, 48, Oleska Street, 45-052 Opole (Poland); Kupka, Teobald, E-mail: teobaldk@gmail.com, E-mail: farhod.nozirov@gmail.com

2014-04-14T23:59:59.000Z

133

Webs in vitro and in vivo: spiders alter their orb-web spinning behavior in the laboratory Andrew Sensenig1,3  

E-Print Network [OSTI]

Webs in vitro and in vivo: spiders alter their orb-web spinning behavior in the laboratory Andrew of the elegant architectures of orb webs are conducted in controlled laboratory environments that remove in the wild is largely unknown. We compared web architecture and silk investment of furrowed orb weavers

Agnarsson, Ingi

134

Interacting spins and holes in zigzag edge nanographene  

SciTech Connect (OSTI)

We have investigated charge and spin gap properties of zigzag edge graphene nanoribbons (ZGNRs) modeled within Hubbard Hamiltonian with onsite electron-electron interaction using semi-empirical many-body configuration interaction (CI) method. The charge gap behavior resembles the mean-field results, showing minima near Dirac point. We have observed unprecedented gap-less spin excitations over the flat band region. Moreover, doping the ZGNRs with holes reduces both the charge and spin gaps, inducing metallic and magnetic behavior, which can be exploited to fabricate spintronic devices.

Dutta, Sudipta; Wakabayashi, Katsunori [International Center for Materials Nanoarchitechtonics (WPI-MANA) National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki - 305-0044 (Japan)

2013-12-04T23:59:59.000Z

135

Muon spin relaxation studies of incommensurate magnetism and superconductivity in stage-4 La2CuO4.11 and La1.88Sr0.12CuO4  

E-Print Network [OSTI]

Muon spin relaxation studies of incommensurate magnetism and superconductivity in stage-4 La2CuO4-0011, Japan Received 1 February 2002; published 16 July 2002 We report muon spin relaxation ( SR) measurements, zero-field SR measurements show muon spin precession below the Ne´el temperature TN with frequency 3

136

Magnetism in fcc rhodium and palladium  

Science Journals Connector (OSTI)

First-principles total-energy band calculations using the fixed-spin-moment procedure are used to study the volume dependence of the magnetic behavior for fcc Rh and Pd. We calculate the total energy, the magnetic moment, and the spin-polarized l-decomposed electron occupancy from below the equilibrium volume to the free-atom limit, and show the magnetic susceptibility in the nonmagnetic range. We find that both metals are nonmagnetic at zero pressure, but undergo first-order transitions from nonmagnetic to magnetic behavior at expanded volumes. In both cases, the onset of magnetic behavior is accompanied by magnetic moments that exceed the Hund’s-rule atomic limit. With increasing volume, we find a depletion of s and p states and a corresponding increase of d states with an approach to the 4d9 and 4d10 free-atom configurations for Rh and Pd, respectively.

V. L. Moruzzi and P. M. Marcus

1989-01-01T23:59:59.000Z

137

Magnetic impurities in graphene  

Science Journals Connector (OSTI)

We used a quantum Monte Carlo method to study the magnetic impurity adatoms on graphene. We found that by tuning the chemical potential we could switch the values of the impurity local magnet moment between relatively large and small values. Our computations of the impurity spectral density found its behavior to differ significantly from that of an impurity in a normal metal and our computations of the charge-charge and spin-spin correlations between the impurity and the conduction-band electrons found them to be strongly suppressed. In general, our results are consistent with those from poor man’s scaling and numerical renormalization group methods.

F. M. Hu; Tianxing Ma; Hai-Qing Lin; J. E. Gubernatis

2011-08-03T23:59:59.000Z

138

Power-Law NLED-Based Magnetic Universe Can Mimic Phantom Behavior  

E-Print Network [OSTI]

We study the cosmic dynamics of a magnetic universe supported by non-linear electrodynamics (NLED) Lagrangeans that are proportional to powers of the electromagnetic invariant $\\propto F^{1/(1-m)}$ ($m$ is an overall constant). For simplicity we focus in the case when $F$ depends on the magnetic field alone, a case dubbed in the bibliography as ''magnetic universe''. Our results demonstrate that, depending on the values of the free parameter $m$, the magnetic field can mimic phantom field behavior, an effect previously found in other contexts. It is demonstrated that, since there are found equilibrium points in the phase space of these models that can be associated with magnetic-dominated past and future attractors, a combination of positive and negative powers of $F$ may lead to interesting cosmological behavior. In particular, a cosmological scenario where the universe might evolve from a past NLED-driven (non-inflationary) state into a future (late-time) -- also NLED-driven -- inflationary stage, transiting through a matter-dominated solution, is envisioned. The impact of braneworld gravity on the dynamics driven by such NLED Lagrangeans is also investigated. It is demonstrated that, due to phantom property at late times, the non-linear electromagnetic effects may play an important role in deciding the fate of the cosmic evolution. Randall-Sundrum brane effects, in particular, modify the nature of the starting point of the cosmic evolution, as well as the fate of the expansion: both, the big bang singularity and the big rip event -- inherent in general relativity with phantom matter source --, may be avoided.

Ricardo García-Salcedo; Tame Gonzalez; Claudia Moreno; Israel Quiros

2010-06-11T23:59:59.000Z

139

Enhanced magnetism and nuclear ordering of 169Tm spins in TmPO4 C. Fermon, J. F. Gregg(*), J.-F. Jacquinot, Y. Roinel, V. Bouffard, G. Fournier and A. Abragam  

E-Print Network [OSTI]

1053 « Enhanced » magnetism and nuclear ordering of 169Tm spins in TmPO4 C. Fermon, J. F. Gregg.P.A.). Abstract 2014 Ordering of the nuclear spins of169Tm in TmPO4, caused by their « enhanced » nuclear magnetism, has been produced by Dynamic Nuclear Polarization (D.N.P.) followed by Adiabatic Demagnetization

Boyer, Edmond

140

Energy levels and decoherence properties of single electron and nuclear spins in a defect center in diamond  

E-Print Network [OSTI]

The coherent behavior of the single electron and single nuclear spins of a defect center in diamond and a 13C nucleus in its vicinity, respectively, are investigated. The energy levels associated with the hyperfine coupling of the electron spin of the defect center to the 13C nuclear spin are analyzed. Methods of magnetic resonance together with optical readout of single defect centers have been applied in order to observe the coherent dynamics of the electron and nuclear spins. Long coherence times, in the order of microseconds for electron spins and tens of microseconds for nuclear spins, recommend the studied system as a good experimental approach for implementing a 2-qubit gate.

I. Popa; T. Gaebel; M. Domhan; C. Wittmann; F. Jelezko; J. Wrachtrup

2004-09-12T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Spin and Charge Quantum Transport in Organic/Magnetic Heterostructures for Spintronics and Optoelectronic  

E-Print Network [OSTI]

and Optoelectronic This research project is one of the Seed Projects of the Caltech Center for Science to optimizing the spintronic and optoelectronic properties of organic semiconductor/ferromagnet heterostructures they are highly adaptable and exhibit interesting properties for optoelectronic applications.ii The weak spin

Yeh, Nai-Chang

142

Devices and process for high-pressure magic angle spinning nuclear magnetic resonance  

DOE Patents [OSTI]

A high-pressure magic angle spinning (MAS) rotor is detailed that includes a high-pressure sample cell that maintains high pressures exceeding 150 bar. The sample cell design minimizes pressure losses due to penetration over an extended period of time.

Hoyt, David W; Sears, Jr., Jesse A; Turcu, Romulus V.F.; Rosso, Kevin M; Hu, Jian Zhi

2014-04-08T23:59:59.000Z

143

Dopant spin states and magnetism of Sn{sub 1?x}Fe{sub x}O{sub 2} nanoparticles  

SciTech Connect (OSTI)

This work reports detailed investigations of a series of ?2.6?nm sized, Sn{sub 1?x}Fe{sub x}O{sub 2} crystallites with x?=?0–0.10 using Mossbauer spectroscopy, x-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance spectroscopy (EPR), and magnetometry to determine the oxidation state of Fe dopants and their role in the observed magnetic properties. The magnetic moment per Fe ion ? was the largest ?6.48?×?10{sup ?3} ?{sub B} for the sample with the lowest (0.001%) Fe doping, and it showed a rapid downward trend with increasing Fe doping. Majority of the Fe ions are in 3+ oxidation state occupying octahedral sites. Another significant fraction of Fe dopant ions is in 4+ oxidation state and a still smaller fraction might be existing as Fe{sup 2+} ions, both occupying distorted sites, presumably in the surface regions of the nanocrystals, near oxygen vacancies. These studies also suggest that the observed magnetism is not due to exchange coupling between Fe{sup 3+} spins. A more probable role for the multi-valent Fe ions may be to act as charge reservoirs, leading to charge transfer ferromagnetism.

Punnoose, A., E-mail: apunnoos@boisestate.edu; Dodge, Kelsey; Reddy, K. M.; Franco, Nevil; Chess, Jordan; Eixenberger, Josh [Department of Physics, Boise State University, Boise, Idaho 83725-1570 (United States); Beltrán, J. J. [Department of Physics, Boise State University, Boise, Idaho 83725-1570 (United States); Grupo de Estado Sólido, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No 52-21, Medellín (Colombia); Barrero, C. A. [Grupo de Estado Sólido, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No 52-21, Medellín (Colombia)

2014-05-07T23:59:59.000Z

144

Micromagnetic study of auto-oscillation modes in spin-Hall nano-oscillators  

SciTech Connect (OSTI)

We present a numerical study of magnetization dynamics in a recently introduced spin torque nano-oscillator, whose operational principle relies on the spin-Hall effect—spin-Hall nano-oscillators. Our numerical results show good agreement with the experimentally observed behaviors and provide detailed information about the features of the primary auto-oscillation mode observed in the experiments. They also clarify the physical nature of the secondary auto-oscillation mode, which was experimentally observed under certain conditions only.

Ulrichs, H., E-mail: henning.ulrichs@uni-muenster.de; Demidov, V. E.; Demokritov, S. O. [Department of Physics and Center for Nonlinear Science, University of Münster, Corrensstraße 2-4, 48149 Münster (Germany)

2014-01-27T23:59:59.000Z

145

Spin Waves and magnetic exchange interactions in insulating Rb0.89Fe1.58Se2  

SciTech Connect (OSTI)

The parent compounds of iron pnictide superconductors are bad metals with a collinear antiferromagnetic structure and Neel temperatures below 220 K. Although alkaline iron selenide A{sub y}Fe{sub 1.6+x}Se{sub 2} (A = K, Rb, Cs) superconductors are isostructural with iron pnictides, in the vicinity of the undoped limit they are insulators, forming a block antiferromagnetic order and having Neel temperatures of roughly 500 K. Here we show that the spin waves of the insulating antiferromagnet Rb{sub 0.89}Fe{sub 1.58}Se{sub 2} can be accurately described by a local moment Heisenberg Hamiltonian. A fitting analysis of the spin wave spectra reveals that the next-nearest neighbour couplings in Rb{sub 0.89}Fe{sub 1.58}Se{sub 2}, (Ba,Ca,Sr)Fe{sub 2}As{sub 2}, and Fe{sub 1.05}Te are of similar magnitude. Our results suggest a common origin for the magnetism of all the Fe-based superconductors, despite having different ground states and antiferromagnetic orderings.

Wang, Miaoyin [ORNL; Fang, Chen [Purdue University; Yao, Dao-Xin [unknown; Tan, Guotai [ORNL; Harriger, Leland W [ORNL; Song, Yu [ORNL; Netherton, Tucker J [ORNL; Zhang, Chenglin [ORNL; Wang, Meng [ORNL; Stone, Matthew B [ORNL; Tian, Wei [Ames Laboratory and Iowa State University; Hu, Jiangping [Purdue University and Chinese Academy of Sciences; Dai, Pengcheng [University of Tennessee, Knoxville (UTK)

2011-01-01T23:59:59.000Z

146

ARPES Provides Direct Evidence of Spin-Wave Coupling  

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

ARPES Provides Direct Evidence of Spin-Wave Coupling Print ARPES Provides Direct Evidence of Spin-Wave Coupling Print The electronic properties of a metal are determined by the dynamical behavior of its conduction electrons. Conventional band theory accounts for the interaction of the electrons with the static ion lattice. However, coupling to further microscopic degrees of freedom can alter the electron dynamics considerably. For example, "conventional" superconductivity emerges as a result of the electrons' interaction with lattice vibrations (phonons). In magnetic materials, coupling with spin waves (magnons) is also expected. Such interactions may contribute to high-temperature superconductivity in novel materials. Unfortunately, lattice vibrations and spin waves have similar energy scales, hindering detailed study. Researchers have taken a new approach in analyzing the electron bands of ferromagnetic iron. Angle-resolved photoemission spectroscopy (ARPES) provides direct spectroscopic evidence of altered electron mass and energy (quasiparticle formation) in a magnetic solid due to coupling with spin waves.

147

ARPES Provides Direct Evidence of Spin-Wave Coupling  

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

ARPES Provides Direct Evidence of Spin-Wave Coupling Print ARPES Provides Direct Evidence of Spin-Wave Coupling Print The electronic properties of a metal are determined by the dynamical behavior of its conduction electrons. Conventional band theory accounts for the interaction of the electrons with the static ion lattice. However, coupling to further microscopic degrees of freedom can alter the electron dynamics considerably. For example, "conventional" superconductivity emerges as a result of the electrons' interaction with lattice vibrations (phonons). In magnetic materials, coupling with spin waves (magnons) is also expected. Such interactions may contribute to high-temperature superconductivity in novel materials. Unfortunately, lattice vibrations and spin waves have similar energy scales, hindering detailed study. Researchers have taken a new approach in analyzing the electron bands of ferromagnetic iron. Angle-resolved photoemission spectroscopy (ARPES) provides direct spectroscopic evidence of altered electron mass and energy (quasiparticle formation) in a magnetic solid due to coupling with spin waves.

148

Pulsar wind model for the spin-down behavior of intermittent pulsars  

E-Print Network [OSTI]

It is observed that intermittent pulsars have higher slow down rate in the on state (radio-loud) than in the off state (radio-quiet). This gives the evidence that particle wind may play an important role in pulsar spindown. The effect of particle acceleration is included in modeling the rotational energy loss rate. Applying the pulsar wind model to the three intermittent pulsars (PSR B1931+24, PSR J1841-0500, and PSR J1832+0029), we calculate their magnetic field and inclination angle simultaneously. The braking index of intermittent pulsars is also predicted. The duty cycle of particle wind determined from timing observations is consistent with the duty cycle of the on state. It is shown that the particle number density may always be the Goldreich-Julian density. This may ensure that different on states of intermittent pulsars are stable. Observations on the inclination angle and braking index of intermittent pulsars may help to test different models of particle acceleration, as well as different models of p...

Li, L; Yan, W M; Yuan, J P; Xu, R X; Wang, N

2013-01-01T23:59:59.000Z

149

Magnetization process, bipartite entanglement, and enhanced magnetocaloric effect of the exactly solved spin-1/2 Ising-Heisenberg tetrahedral chain  

Science Journals Connector (OSTI)

The frustrated spin-1/2 Ising-Heisenberg ladder with Heisenberg intra-rung and Ising inter-rung interactions is exactly solved in a longitudinal magnetic field by taking advantage of the local conservation of the total spin on each rung and the transfer-matrix method. We have rigorously calculated the ground-state phase diagram, magnetization process, magnetocaloric effect, and basic thermodynamic quantities for the model, which can be alternatively viewed as an Ising-Heisenberg tetrahedral chain. It is demonstrated that a stepwise magnetization curve with an intermediate plateau at half of the saturation magnetization is also reflected in respective stepwise changes of the concurrence serving as a measure of bipartite entanglement. The ground-state phase diagram and zero-temperature magnetization curves of the Ising-Heisenberg tetrahedral chain are contrasted with the analogous results of the purely quantum Heisenberg tetrahedral chain, which have been obtained through density-matrix renormalization group (DMRG) calculations. While both ground-state phase diagrams fully coincide in the regime of weak inter-rung interaction, the purely quantum Heisenberg tetrahedral chain develops Luttinger spin-liquid and Haldane phases for strongly coupled rungs, which are absent in the Ising-Heisenberg counterpart model.

Jozef Stre?ka; Onofre Rojas; Taras Verkholyak; Marcelo L. Lyra

2014-02-28T23:59:59.000Z

150

Terahertz Spectroscopy of Spin Waves in Multiferroic BiFeO3 in High Magnetic Fields  

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

We have studied the magnetic field dependence of far-infrared active magnetic modes in a single ferroelectric domain BiFeO3 crystal at low temperature. The modes soften close to the critical field of 18.8 T along the [001] (pseudocubic) axis, where the cycloidal structure changes to the homogeneous canted antiferromagnetic state and a new strong mode with linear field dependence appears that persists at least up to 31 T. A microscopic model that includes two Dzyaloshinskii-Moriya interactions and easy-axis anisotropy describes closely both the zero-field spectroscopic modes as well as their splitting and evolution in a magnetic field. The good agreement of theory with experiment suggests that the proposed model provides the foundation for future technological applications of this multiferroic material.

Nagel, U.; Fishman, Randy S.; Katuwal, T.; Engelkamp, H.; Talbayev, D.; Yi, Hee Taek; Cheong, S.-W.; Rõõm, T.

2013-06-01T23:59:59.000Z

151

Interface boundary conditions for dynamic magnetization and spin wave dynamics in a ferromagnetic layer with the interface Dzyaloshinskii-Moriya interaction  

SciTech Connect (OSTI)

In this work, we derive the interface exchange boundary conditions for the classical linear dynamics of magnetization in ferromagnetic layers with the interface Dzyaloshinskii-Moriya interaction (IDMI). We show that IDMI leads to pinning of dynamic magnetization at the interface. An unusual peculiarity of the IDMI-based pinning is that its scales as the spin-wave wave number. We incorporate these boundary conditions into an existing numerical model for the dynamics of the Damon-Eshbach spin wave in ferromagnetic films. IDMI affects the dispersion and the frequency non-reciprocity of the travelling Damon-Eshbach spin wave. For a broad range of film thicknesses L and wave numbers, the results of the numerical simulations of the spin wave dispersion are in a good agreement with a simple analytical expression, which shows that the contribution of IDMI to the dispersion scales as 1/L, similarly to the effect of other types of interfacial anisotropy. Suggestions to experimentalists how to detect the presence of IDMI in a spin wave experiment are given.

Kostylev, M. [School of Physics, M013, University of Western Australia, Crawley, Perth 6009, Western Australia (Australia)

2014-06-21T23:59:59.000Z

152

Non-Linear Magnetic Ringing of Spin-Ordered Solid He-3  

E-Print Network [OSTI]

of preparing the initial state, not by switch- ing off a large dc field, but rather by applying a ~eak ac magnetic pulse at the zero-field resonance fre- quency IIp/2rr for a sufficient duration, in order to drive the system to a finite deviation from...

Hu, Chia-Ren; HAM, TE.

1981-01-01T23:59:59.000Z

153

Anisotropic Spin Relaxation in Graphene  

Science Journals Connector (OSTI)

Spin relaxation in graphene is investigated in electrical graphene spin valve devices in the nonlocal geometry. Ferromagnetic electrodes with in-plane magnetizations inject spins parallel to the graphene layer. They are subject to Hanle spin precession under a magnetic field B applied perpendicular to the graphene layer. Fields above 1.5 T force the magnetization direction of the ferromagnetic contacts to align to the field, allowing injection of spins perpendicular to the graphene plane. A comparison of the spin signals at B=0 and B=2??T shows a 20% decrease in spin relaxation time for spins perpendicular to the graphene layer compared to spins parallel to the layer. We analyze the results in terms of the different strengths of the spin-orbit effective fields in the in-plane and out-of-plane directions and discuss the role of the Elliott-Yafet and Dyakonov-Perel mechanisms for spin relaxation.

N. Tombros; S. Tanabe; A. Veligura; C. Jozsa; M. Popinciuc; H. T. Jonkman; B. J. van Wees

2008-07-25T23:59:59.000Z

154

Spin and orbital magnetism of coinage metal trimers (Cu{sub 3}, Ag{sub 3}, Au{sub 3}): A relativistic density functional theory study  

SciTech Connect (OSTI)

We have demonstrated electronic structure and magnetic properties of Cu{sub 3}, Ag{sub 3} and Au{sub 3} trimers using a full potential local orbital method in the framework of relativistic density functional theory. We have also shown that the non-relativistic generalized gradient approximation for the exchange-correlation energy functional gives reliable magnetic properties in coinage metal trimers compared to experiment. In addition we have indicated that the spin-orbit coupling changes the structure and magnetic properties of gold trimer while the structure and magnetic properties of copper and silver trimers are marginally affected. A significant orbital moment of 0.21?{sub B} was found for most stable geometry of the gold trimer whereas orbital magnetism is almost quenched in the copper and silver trimers.

Afshar, Mahdi [Department of Physics, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)] [Department of Physics, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Sargolzaei, Mohsen [Department of Chemistry, Shahrood University of Technology, Shahrood (Iran, Islamic Republic of)] [Department of Chemistry, Shahrood University of Technology, Shahrood (Iran, Islamic Republic of)

2013-11-15T23:59:59.000Z

155

Magnetism and magnetotransport in disordered graphene  

Science Journals Connector (OSTI)

We perform Monte Carlo simulations to study the interplay of structural and magnetic order in single layer graphene covered with magnetic adatoms. We propose that the presence of ripples in the graphene structure can lead to clustering of the adatoms and to a variety of magnetic states such as superparamagnetism, antiferromagnetism, ferromagnetism and spin-glass behavior. We derive the magnetization hysteresis and also the magnetoresistance curves in the variable range hopping regime, which can provide experimental signatures for ripple induced clustering and magnetism. We propose that the magnetic states in graphene can be controlled by gate voltage and coverage fraction.

T. G. Rappoport; Bruno Uchoa; A. H. Castro Neto

2009-12-07T23:59:59.000Z

156

Synthesis, characterization and magnetic behavior of Co/MCM-41 nano-composites  

SciTech Connect (OSTI)

Synthesis, structure and magnetic properties of Co/MCM-41 as magnetic nano-composites have been investigated. Mesoporous materials with different degrees of metal loading were prepared by wet impregnation and characterized by ICP, XRD, N{sub 2} adsorption, UV–vis DRS, TPR and EPMA-EDS. Cobalt oxide clusters and Co{sub 3}O{sub 4} nano-particles could be confined inside the mesopores of MCM-41, being this fact favored by the Co loading increasing. In addition, larger crystals of Co{sub 3}O{sub 4} detectable by XRD also grow on the surface when the Co loading is enhanced. The magnetic characterization was performed in a SQUID magnetometer using a maximum magnetic applied field µ{sub 0}Ha=1 T. While the samples with the higher Co loadings showed a behavior typically paramagnetic, a superparamagnetic contribution is more notorious for lower loadings, suggesting high Co species dispersion. - Graphical abstract: Room temperature hysteresis loops as a function of the Co content. Display Omitted - Highlights: • Co species as isolated Co{sup 2+}, oxide clusters and Co{sub 3}O{sub 4} nano-particles were detected. • For higher Co loads were detected, by XRD, Co{sub 3}O{sub 4} particles on the external surface. • The confining of Co species inside the mesopores was achieved by increasing Co load. • Paramagnetism from oxide clusters/nano-particles becomes dominant for higher Co loads. • Superparamagnetism can be assigned to Co species of small size and finely dispersed.

Cuello, N. [CITeQ-Universidad Tecnológica Nacional-Facultad Regional Córdoba, Maestro López esq. Cruz Roja Argentina, 5016 Córdoba (Argentina); Elías, V. [CITeQ-Universidad Tecnológica Nacional-Facultad Regional Córdoba, Maestro López esq. Cruz Roja Argentina, 5016 Córdoba (Argentina); CONICET (Argentina); Crivello, M. [CITeQ-Universidad Tecnológica Nacional-Facultad Regional Córdoba, Maestro López esq. Cruz Roja Argentina, 5016 Córdoba (Argentina); Oliva, M. [FaMAF-Universidad Nacional de Córdoba, Córdoba (Argentina); IFEG-CONICET (Argentina); Eimer, G., E-mail: geimer@scdt.frc.utn.edu.ar [CITeQ-Universidad Tecnológica Nacional-Facultad Regional Córdoba, Maestro López esq. Cruz Roja Argentina, 5016 Córdoba (Argentina); CONICET (Argentina)

2013-09-15T23:59:59.000Z

157

Ising-Glauber Spin Cluster Model for Temperature-Dependent Magnetization Noise in SQUIDs  

Science Journals Connector (OSTI)

Clusters of interacting two-level-systems, likely due to Farbe+(F+) centers at the metal-insulator interface, are shown to self-consistently lead to 1/f? magnetization noise [with ?(T)?1] in SQUIDs. Model calculations, based on a new method of obtaining correlation functions, explains various puzzling experimental features. It is shown why the inductance noise is inherently temperature dependent while the flux noise is not, despite the same underlying microscopics. Magnetic ordering in these systems, established by three-point correlation functions, explains the observed flux- inductance-noise cross correlations. Since long-range ferromagnetic interactions are shown to lead to a more weakly temperature dependent flux noise when compared to short-range interactions, the time reversal symmetry of the clusters is also not likely broken by the same mechanism which mediates surface ferromagnetism in nanoparticles and thin films of the same insulator materials.

Amrit De

2014-11-18T23:59:59.000Z

158

RHIC | Spin Physics  

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

Spin Physics Spin Physics RHIC is the world's only machine capable of colliding high-energy beams of polarized protons, and is a unique tool for exploring the puzzle of the proton's 'missing' spin. In addition to colliding heavy ions, RHIC is able to collide single protons. While these collisions don't produce quark-gluon plasma, they're interesting to physicists for other reasons. Scientists want to know more about a property of particles called 'spin'. Spin is the direction a particle is spinning around an axis as it travels -- just like the Earth spins on its axis as it travels around the sun. Each proton has a specific spin, which helps give it a characteristic magnetic property. spin In this picture of a proton-proton collision, the spin of the particles is shown as arrows circling the spherical particles. The red and green

159

A New Spin on Photoemission Spectroscopy  

SciTech Connect (OSTI)

The electronic spin degree of freedom is of general fundamental importance to all matter. Understanding its complex roles and behavior in the solid state, particularly in highly correlated and magnetic materials, has grown increasingly desirable as technology demands advanced devices and materials based on ever stricter comprehension and control of the electron spin. However, direct and efficient spin dependent probes of electronic structure are currently lacking. Angle Resolved Photoemission Spectroscopy (ARPES) has become one of the most successful experimental tools for elucidating solid state electronic structures, bolstered bycontinual breakthroughs in efficient instrumentation. In contrast, spin-resolved photoemission spectroscopy has lagged behind due to a lack of similar instrumental advances. The power of photoemission spectroscopy and the pertinence of electronic spin in the current research climate combine to make breakthroughs in Spin and Angle Resolved Photoemission Spectroscopy (SARPES) a high priority . This thesis details the development of a unique instrument for efficient SARPES and represents a radical departure from conventional methods. A custom designed spin polarimeter based on low energy exchange scattering is developed, with projected efficiency gains of two orders of magnitude over current state-of-the-art polarimeters. For energy analysis, the popular hemispherical analyzer is eschewed for a custom Time-of-Flight (TOF) analyzer offering an additional order of magnitude gain in efficiency. The combined instrument signifies the breakthrough needed to perform the high resolution SARPES experiments necessary for untangling the complex spin-dependent electronic structures central to today?s condensed matter physics.

Advanced Light Source; Jozwiak, Chris

2008-12-18T23:59:59.000Z

160

Bonding, Backbonding, and Spin-Polarized Molecular Orbitals: Basis for Magnetism and Semiconducting Transport in V[TCNE]x~;;2  

E-Print Network [OSTI]

Orbitals: Basis for Magnetism and Semiconducting Transportand photo-induced magnetism [6, 7]. These novel propertiesthe former LUMO splitting. Magnetism and activated transport

Kortright, Jeffrey B

2008-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Observation of Transient Behavior of Magnetic Flux in Inductive-type Fault Current Limiter with YBCO Thin Film Disc  

Science Journals Connector (OSTI)

Recently, the installation of fault current limiters (FCLs) in power systems is expected for controlling large short circuit currents. In this study, we focus on inductive-type \\{FCLs\\} having a YBCO superconducting thin film disc that is fabricated by metal-organic deposition. AC currents were injected into the FCL so that the periodic transient behavior of the apparent magnetic flux density around the FCL could be measured by using a pick-up coil. The magnetic flux density exhibited hysteresis when AC current was injected into the FCL. The transition between the conducting states in the YBCO layer was explained by the hysteresis relationship between the magnetic flux density and current.

Kosuke Higuchi; Yin Guan; Yasunobu Yokomizu; Toshiro Matsumura

2012-01-01T23:59:59.000Z

162

Nuclear Spin Filter  

Science Journals Connector (OSTI)

A "spin filter" for selecting metastable hydrogen, deuterium, or tritium atoms with a given nuclear spin magnetic quantum number (mI) has been built and tested. With the device installed in the Los Alamos "Lamb-shift" polarized-ion source, we have obtained a deuterium negative-ion beam with ? 55% spin-state purity for mI=1, 0, or -1. An improved magnetic field homogeneity in the apparatus is expected to increase the purity to ? 75%.

Joseph L. McKibben; George P. Lawrence; Gerald G. Ohlsen

1968-05-20T23:59:59.000Z

163

Spin-gap opening accompanied by a strong magnetoelastic response in the S=1 magnetic dimer system Ba3BiRu2O9  

Science Journals Connector (OSTI)

Neutron diffraction, magnetization, resistivity, and heat-capacity measurements on the 6H-perovskite Ba3BiRu2O9 reveal simultaneous magnetic and structural dimerization driven by strong magnetoelastic coupling. An isostructural but strongly displacive first-order transition on cooling through T*=176 K is associated with a change in the nature of direct Ru–Ru bonds within Ru2O9 face-sharing octahedra. Above T*, Ba3BiRu2O9 is an S=1 magnetic dimer system with intradimer exchange interactions J0/kB=320 K and interdimer exchange interactions J?/kB=?160 K. Below T*, a spin-gapped state emerges with ??220 K. Ab initio calculations confirm antiferromagnetic exchange within dimers, but the transition is not accompanied by long-range magnetic order.

Wojciech Miiller; Maxim Avdeev; Qingdi Zhou; Andrew J. Studer; Brendan J. Kennedy; Gordon J. Kearley; Chris D. Ling

2011-12-15T23:59:59.000Z

164

Deconvolution of mixed magnetism in multilayer graphene  

SciTech Connect (OSTI)

Magnetic properties of graphite modified at the edges by KCl and exfoliated graphite in the form of twisted multilayered graphene (<4 layers) are analyzed to understand the evolution of magnetic behavior in the absence of any magnetic impurities. The mixed magnetism in multilayer graphene is deconvoluted using Low field-high field hysteresis loops at different temperatures. In addition to temperature and the applied magnetic field, the density of edge state spins and the interaction between them decides the nature of the magnetic state. By virtue of magnetometry and electron spin resonance studies, we demonstrate that ferromagnetism is intrinsic and is due to the interactions among various paramagnetic centers. The strength of these magnetic correlations can be controlled by modifying the structure.

Swain, Akshaya Kumar [IITB-Monash Research Academy, Department of Metallurgical Engineering and Materials Science, IIT Bombay, Mumbai 400076 (India); Bahadur, Dhirendra, E-mail: dhirenb@iitb.ac.in [Department of Metallurgical Engineering and Materials Science, IIT Bombay, Mumbai 400076 (India)

2014-06-16T23:59:59.000Z

165

Phase transitions and entanglement properties in spin-1 Heisenberg clusters with single-ion anisotropy  

E-Print Network [OSTI]

The incipient quantum phase transitions of relevance to nonzero fluctuations and entanglement in Heisenberg clusters are studied in this paper by exploiting negativity as a measure in bipartite and frustrated spin-1 anisotropic Heisenberg clusters with bilinear-biquadratic exchange, single-ion anisotropy and magnetic field. Using the exact diagonalization technique, it is shown that quantum critical points signaled by qualitative changes in behavior of magnetization and particle number are ultimately related to microscopic entanglement and collective excitations. The plateaus and peaks in spin and particle susceptibilities define the conditions for a high/low-density quantum entanglement and various ordered phases with different spin (particle) concentrations.

V S Abgaryan; N S Ananikian; L N Ananikyan; A N Kocharian

2011-06-27T23:59:59.000Z

166

Hydrogenated Graphene Nanoflakes: Semiconductor to Half-Metal Transition and Remarkable Large Magnetism  

SciTech Connect (OSTI)

The electronic and magnetic properties of graphene nanoflakes (GNFs) can be tuned by patterned adsorption of hydrogen. Controlling the H coverage from bare GNFs to half hydrogenated and then to fully hydrogenated GNFs, the transformation of small-gap semiconductor {yields} half-metal {yields} wide-gap semiconductor occurs, accompanied by a magnetic {yields} magnetic {yields} nonmagnetic transfer and a nonmagnetic {yields} magnetic {yields} nonmagnetic transfer for triangular and hexagonal nanoflakes, respectively. The half hydrogenated GNFs, associated with strong spin polarization around the Fermi level, exhibit the unexpected large spin moment that is scaled squarely with the size of flakes. The induced spin magnetizations of these nanoflakes align parallel and lead to a substantial collective character, enabling the half hydrogenated GNFs to be spin-filtering flakes. These hydrogenation-dependent behaviors are then used to realize an attractive approach to engineer the transport properties, which provides a new route to facilitate the design of tunable spin devices.

Zhou, Yungang; Wang, Zhiguo; Yang, Ping; Sun, Xin; Zu, Xiaotao; Gao, Fei

2012-03-08T23:59:59.000Z

167

E-Print Network 3.0 - anomalous magnetic behavior Sample Search...  

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

of Physics, University of Maryland at College Park Collection: Engineering ; Materials Science 3 Probing the magnetic microstructure of an amorphous GdFe system with magnetic...

168

Phonon and magnetic dimer excitations in Fe-based S=2 spin-ladder compound BaFe2Se2O  

Science Journals Connector (OSTI)

Raman scattering spectra of the new Fe-based S=2 spin-ladder compound BaFe2Se2O are measured in a temperature range between 15 and 623 K. All six A1g and two B1g Raman active modes of BaFe2Se2O, predicted by the factor-group analysis, have been experimentally observed at energies that are in a rather good agreement with the lattice dynamics calculation. The antiferromagnetic long-range spin ordering in BaFe2Se2O below TN=240 K leaves a fingerprint both in the A1g and B1g phonon mode linewidth and energy. In the energy range between 400 and 650 cm?1 we have observed a magnetic excitation related structure in the form of a magnon continuum, with the peaks corresponding to the singularities in the one-dimensional density of magnon states. The onset value of magnetic continuum (2?S) is found at about 437 cm?1 at 15 K. The magnetic continuum disappears at about 623 K, which led us to conclude that the short-range magnetic ordering in BaFe2Se2O exists apparently up to 2.6TN.

Z. V. Popovi?; M. Š?epanovi?; N. Lazarevi?; M. M. Radonji?; D. Tanaskovi?; Hechang Lei (???); C. Petrovic

2014-01-03T23:59:59.000Z

169

Crystal structure and magnetic properties and Zn substitution effects on the spin-chain compound Sr{sub 3}Co{sub 2}O{sub 6}  

SciTech Connect (OSTI)

The effects of substituting Co on the spin-chain compound Sr{sub 3}Co{sub 2}O{sub 6} with Zn were investigated by synchrotron X-ray diffraction, magnetic susceptibility, isothermal magnetization, and specific heat measurements. To the best of our knowledge, this is the first report to describe the successful substitution of Co in Sr{sub 3}Co{sub 2}O{sub 6} with Zn. The substitution was carried out by a method involving high pressures and temperatures to obtain Sr{sub 3}CoZnO{sub 6}, which crystalized into a K{sub 4}CdCl{sub 6}-derived rhombohedral structure with a space group of R-3c, similar to the host compound. With the Zn substitution, the Ising-type magnetic anisotropy of the host compound remarkably reduced; the newly formed Sr{sub 3}CoZnO{sub 6} became magnetically isotropic with Heisenberg-type characteristics. This could probably be ascribed to the establishment of a different interaction pathway, –Co{sup 4+}(S=1/2)–O–Zn{sup 2+}(S=0)–O–Co{sup 4+}(S=1/2)–. Details of the magnetic properties of Zn substituted Sr{sub 3}Co{sub 2}O{sub 6} were reported. - Graphical abstract: Crystal structure of the spin-chain compound Sr{sub 3}CoZnO{sub 6} synthesized at 6 GPa. Zn atoms preferably occupy the trigonal prism sites rather than the octahedral sites. As a result, the compound is much magnetically isotropic. Highlights: • Effects of substituting Co with Zn on spin-chain magnetism of Sr{sub 3}Co{sub 2}O{sub 6} were studied. • High-pressure synthesis resulted in a solid solution of Sr{sub 3}CoZnO{sub 6}. • Sr{sub 3}CoZnO{sub 6} showed more isotropic magnetism than the host Sr{sub 3}Co{sub 2}O{sub 6}.

Wang, Xia [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba Ibaraki 305-0044 (Japan); Department of Chemistry, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Guo, Yanfeng, E-mail: Yangfeng.Guo@physics.ox.ac.uk [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba Ibaraki 305-0044 (Japan); Sun, Ying [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba Ibaraki 305-0044 (Japan); Tsujimoto, Yoshihiro [Materials Processing Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba Ibaraki 305-0047 (Japan); Matsushita, Yoshitaka [Materials Analysis Station, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba Ibaraki 305-0047 (Japan); Yamaura, Kazunari, E-mail: yamaura.kazunari@nims.go.jp [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba Ibaraki 305-0044 (Japan); Department of Chemistry, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan)

2013-08-15T23:59:59.000Z

170

Spin Stability  

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

Stability Stability of Asymmetrically Charged Plasma Dust I. H. Hutchinson Plasma Science and Fusion Center Massachusetts Institute of Technology, Cambridge, MA, USA Recently it has been reported that, under some circumstances, dust particles sus- pended in the sheath edge are observed to spin [1, 2, 3]. The present paper shows that there is a natural electrostatic mechanism that should cause even perfectly spherical par- ticles in a perfectly irrotational, magnetic-field-free flowing plasma to spin. The stability criterion and the final spin state are obtained[4]. When the particle is made of an insulating material, it can support potential dif- ferences around its surface. In the limit of zero conductivity, and ignoring all charging effects other than electron or ion collection, the surface charge density accumulates in such a way as to bring the local electric current density to zero.

171

Low-amplitude magnetic vortex core reversal by non-linear interaction between azimuthal spin waves and the vortex gyromode  

SciTech Connect (OSTI)

We show, by experiments and micromagnetic simulations in vortex structures, that an active “dual frequency” excitation of both the sub-GHz vortex gyromode and multi-GHz spin waves considerably changes the frequency response of spin wave mediated vortex core reversal. Besides additional minima in the switching threshold, a significant broadband reduction of the switching amplitudes is observed, which can be explained by non-linear interaction between the vortex gyromode and the spin waves. We conclude that the well known frequency spectra of azimuthal spin waves in vortex structures are altered substantially, when the vortex gyromode is actively excited simultaneously.

Sproll, Markus; Noske, Matthias; Kammerer, Matthias; Dieterle, Georg; Weigand, Markus; Stoll, Hermann; Schütz, Gisela [Max Planck Institute for Intelligent Systems (formerly MPI for Metals Research), Heisenbergstr. 3, 70569 Stuttgart (Germany)] [Max Planck Institute for Intelligent Systems (formerly MPI for Metals Research), Heisenbergstr. 3, 70569 Stuttgart (Germany); Bauer, Hans; Gangwar, Ajay; Woltersdorf, Georg; Back, Christian H. [Department of Physics, University of Regensburg, Universitätsstr. 31, 93040 Regensburg (Germany)] [Department of Physics, University of Regensburg, Universitätsstr. 31, 93040 Regensburg (Germany)

2014-01-06T23:59:59.000Z

172

Photo of the Week: Controlling Chaos with Magnetic Fields | Department of  

Broader source: Energy.gov (indexed) [DOE]

Controlling Chaos with Magnetic Fields Controlling Chaos with Magnetic Fields Photo of the Week: Controlling Chaos with Magnetic Fields January 18, 2013 - 11:26am Addthis This artistic rendition of "spin vortices" illustrates tiny magnetic vortices that spin according to the polarization of each disk's vortex core. At Argonne National Laboratory, scientists are using alternating magnetic fields to control the behavior of these spin vortices, which are small dots made of iron and nickel. The experiments will help to create new, more efficient magnetic devices -- like the random access memory (RAM) in the device you are using to look at this very photo. Learn more about spin vortices. | Photo courtesy of Sander Munster, Dresden University of Technology.

173

Chaotic spin correlations in frustrated Ising hierarchical lattices  

E-Print Network [OSTI]

Spin-spin correlations are calculated in frustrated hierarchical Ising models that exhibit chaotic renormalization-group behavior. The spin-spin correlations, as a function of distance, behave chaotically. The far correlations, ...

Aral, Nese

174

Studies of magnetism and exchange scattering in solids using synchroton radiation and spin-polarized photoemission. Progress report, June 1, 1982-May 31, 1983  

SciTech Connect (OSTI)

Some of the experiments necessary for proving the existence of Spin Polarized EXAFS (SPEXAFS) and for establishing it as a useful techncique for studying magnetism in solids have been carried out at the Stanford Synchrotron Radiation Laboratory (SSRL) and the National Synchrotron Light Source (NSLS). Transmission EXAFS, which does not depend on electron spin, has been measured in several manganese compounds. The 3s photopeaks of Mn/sup 2 +/ in MnF/sub 2/ have been shown to display EXAFS-like oscillations. The pin dependence of these oscillations will next be studied. Observations of the 3p photopeaks of iron metal on a palladium substrate have shown anomalous intensity variations with varying photon energy. This phenomenon will also be studied further. The existence of Cooper minima in the iron 3s and 3p photoabsorption cross sections has been sought, and this investigation will continue.

Rothberg, G.M.

1983-01-01T23:59:59.000Z

175

The asymptotic behavior for the Vlasov-Poisson-Boltzmann system & heliostat with spinning-elevation tracking mode.  

E-Print Network [OSTI]

???Time asymptotic behavior for Boltzmann equations and their derivatives is an interesting and important problem for both physicists and mathematicians. The dynamics of dilute electrons… (more)

Li, Li (??)

2009-01-01T23:59:59.000Z

176

Electric field control of spin-resolved edge states in graphene quantum nanorings  

SciTech Connect (OSTI)

The electric-field effect on the electronic and magnetic properties of triangular and hexagonal graphene quantum rings with zigzag edge termination is investigated by means of the single-band tight-binding Hamiltonian and the mean-field Hubbard model. It is shown how the electron and spin states in the nanoring structures can be manipulated by applying an electric field. We find different spin-depolarization behaviors with variation of electric field strength due to the dependence of spin densities on the shapes and edges of this kind of nanorings. In the case of triangular quantum rings, the magnetization on the inner and outer edges can be selectively tuned and the spin states depolarize gradually as the field strength is increased, while in the case of hexagonal nanorings, the transverse electric field reduces the magnetic moments on both inner and outer edges symmetrically and rapidly.

Farghadan, R., E-mail: rfarghadan@kashanu.ac.ir [Department of Physics, University of Kashan, Kashan (Iran, Islamic Republic of); Saffarzadeh, A. [Department of Physics, Payame Noor University, P.O. Box 19395-3697, Tehran (Iran, Islamic Republic of); Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada)

2014-05-07T23:59:59.000Z

177

Magnetism in tunable quantum rings  

Science Journals Connector (OSTI)

We have studied the spin structure of circular four-electron quantum rings using tunable confinement potentials. The calculations were done using the exact diagonalization method. Our results indicate that ringlike systems can have oscillatory flips between ferromagnetic and antiferromagnetic behavior as a function of the magnetic field. Furthermore, at constant external magnetic fields there were seen similar oscillatory changes between ferromagnetism and antiferromagnetism when the system parameters were changed. According to our results, the magnetism of quantum rings could be tuned by system parameters.

G. Bårdsen; E. Tölö; A. Harju

2009-11-10T23:59:59.000Z

178

Microstructual investigation of mixed rar earth iron boron processed vis melt-spinning and high-pressure gas-atomization for isotrophic bonded permanent magnets  

SciTech Connect (OSTI)

A solid solution of three rare earths (RE) in the RE{sub 2}Fe{sub 14}B structure have been combined to create the novel mixed rare earth iron boron (MRE{sub 2}Fe{sub 14}B) alloy family. MRE{sub 2}Fe{sub 14}B exhibits reduced temperature dependent magnetic properties; remanence and coercivity. The desired form of MRE{sub 2}Fe{sub 14}B is a powder that can be blended with a polymer binder and compression or injection molded to form an isotropic polymer bonded permanent magnet (PBM). Commercially, Nd{sub 2}Fe{sub 14}B is the alloy of choice for PBMs. Powders of Nd{sub 2}Fe{sub 14}B are made via melt-spinning as can be MRE{sub 2}Fe{sub 14}B which allows for direct comparisons. MRE{sub 2}Fe{sub 14}B made using melt-spinning at high wheel speeds is overquenched and must be annealed to an optimal hard magnetic state. Due to the rare earth content in the MRE{sub 2}Fe{sub 14}B powders, they must be protected from the environment in which they operate. This protection is accomplished by using a modified fluidized bed process to grow a protective fluoride coating nominally 15nm thick, to reduce air oxidation. MRE{sub 2}Fe{sub 14}B has demonstrated reduced temperature dependent magnetic properties in ribbon and PBM form. The real challenge has been modifying alloy designs that were successfully melt-spun to be compatible with high-pressure gas-atomization (HPGA). The cooling rates in HPGA are lower than melt-spinning, as the powders are quenched via convective cooling, compared to melt-spinning, which quenches initially by conductive cooling. Early alloy designs, in gas atomized and melt-spun form, did not have similar phase compositions or microstructures. Alloy additions, such as the addition of zirconium as a nucleation catalyst, were successful in creating similar phases and microstructures in the HPGA powders and melt-spun ribbon of the same MRE{sub 2}Fe{sub 14}B composition.

Buelow, Nicholas Lee

2005-08-01T23:59:59.000Z

179

398 IEEE TRANSACTIONS ON MAGNETICS, VOL. 42, NO. 3, MARCH 2006 Introducing Dynamic Behavior of Magnetic Materials  

E-Print Network [OSTI]

of Magnetic Materials Into a Model of a Switched Reluctance Motor Drive F. Sixdenier, L. Morel, and J. P, we present the model of an ultrafast switched reluctance motor, in which the control of the power switched reluctance motor (SRM) drive [9], [10] designed by the Labora- toire de genie industriel et

Boyer, Edmond

180

Quantum states of neutrons in magnetic thin films  

SciTech Connect (OSTI)

We have studied experimentally and theoretically the interaction of polarized neutrons with magnetic thin films and magnetic multilayers. In particular, we have analyzed the behavior of the critical edges for total external reflection in both cases. For a single film we have observed experimentally and theoretically a simple behavior: the critical edges remain fixed and the intensity varies according to the angle between the polarization axis and the magnetization vector inside the film. For the multilayer case we find that the critical edges for spin-up and spin-down polarized neutrons move toward each other as a function of the angle between the magnetization vectors in adjacent ferromagnetic films. Although the results for multilayers and single thick layers appear to be different, in fact, the same spinor method explains both results. An interpretation of the critical edges behavior for the multilyers as a superposition of ferromagnetic and antifferomagnetic states is given.

Radu, F.; Zabel, H. [Department of Physics, Ruhr-University Bochum, D- 44780 Bochum (Germany); Leiner, V. [Institut fuer Werkstoffforschung WFN, GKSS Forschungszentrum GmbH, 21502 Geesthacht (Germany); Wolff, M. [Department of Physics, Ruhr-University Bochum, D- 44780 Bochum (Germany); Institut Laue-Langevin, F-38042 Grenoble Cedex 9 (France); Ignatovich, V.K. [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980, Dubna Moscow Region (Russian Federation)

2005-06-01T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Magnetism  

Science Journals Connector (OSTI)

Historically, magnetism is related to rock magnetism, due to a few minerals exhibiting spontaneous magnetization. Attractive properties of magnetite were already known in Antiquity and were used for navigation...

Guillaume Morin

1998-01-01T23:59:59.000Z

182

Neutron Spin Resonance in Iron-based Superconductors | The Ames...  

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

Neutron Spin Resonance in Iron-based Superconductors The propagation of a novel magnetic excitation in the superconducting state, called a spin resonance, has been observed in iron...

183

Polaron Behavior in CMR Manganites  

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

Polaron Behavior in CMR Manganites Print Polaron Behavior in CMR Manganites Print Spintronic devices manipulate electron spin to sense magnetic fields, store information, or perform logical operations. Colossal magnetoresistive (CMR) manganites are a class of materials under study for future spintronic applications such as nonvolatile magnetic computer memory (MRAM). Researchers have recently used several soft x-ray spectroscopies at the ALS to study a prototypical CMR manganite as it was heated past its Curie temperature-the point at which the material ceases to be magnetic. They were able to observe the formation of polarons: electrons whose interaction with the lattice creates a deformation (energy well) that traps the electron, as a pocket on a pool table traps a billiard ball. For the first time, this provided a direct look inside polaron formation in a CMR material, indicating that electron localization as polarons is a defining characteristic of all CMR materials.

184

Polaron Behavior in CMR Manganites  

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

Polaron Behavior in CMR Manganites Print Polaron Behavior in CMR Manganites Print Spintronic devices manipulate electron spin to sense magnetic fields, store information, or perform logical operations. Colossal magnetoresistive (CMR) manganites are a class of materials under study for future spintronic applications such as nonvolatile magnetic computer memory (MRAM). Researchers have recently used several soft x-ray spectroscopies at the ALS to study a prototypical CMR manganite as it was heated past its Curie temperature-the point at which the material ceases to be magnetic. They were able to observe the formation of polarons: electrons whose interaction with the lattice creates a deformation (energy well) that traps the electron, as a pocket on a pool table traps a billiard ball. For the first time, this provided a direct look inside polaron formation in a CMR material, indicating that electron localization as polarons is a defining characteristic of all CMR materials.

185

magnetism  

Science Journals Connector (OSTI)

magnetism [A class of physical phenomena associated with moving electricity, including the mutual mechanical forces among magnets and electric currents] ? Magnetismus m

2014-08-01T23:59:59.000Z

186

Anomalous magnetic behavior in the transition metal ions doped Cu{sub 2}O flower-like nanostructures  

SciTech Connect (OSTI)

Cuprous oxide (Cu{sub 2}O) flower-like nanostructures doped with various metal ions i.e. Fe, Co, Ni and Mn have been synthesized by an organic phase solution method. The powder X-ray diffraction study clearly reveals them as single phase simple cubic cuprite lattice. Study of their magnetic properties have shown that these doped samples are ferromagnetic in nature; however, no such property was observed for the undoped Cu{sub 2}O sample. The magnitude of the ferromagnetic behavior was found to be dependent on the dopant metal ions amount, which increased consistently with its increase. As total magnetic moment contribution of the doped metal ions calculated was insignificant, it is believed to have originated from the induced magnetic moments at cation deficiency sites in the material, created possibly due to the disturbance of the crystal lattice by the dopant ions. The existence of the defects has been supported by photoluminescence spectra of the doped samples. -- Graphical abstract: Room temperature ferromagnetic behavior was observed in the Cu{sub 2}O nanoflowers doped with Fe, Co, Ni and Mn ions. Cation deficiencies formed due to dopant ions were possibly responsible for ferromagnetism. Display Omitted

Ahmed, Asar [Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh (India); Gajbhiye, Namdeo S., E-mail: nsg@iitk.ac.i [Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh (India)

2011-01-15T23:59:59.000Z

187

Magnetism of individual atoms adsorbed on surfaces Harald Brune a,*, Pietro Gambardella b  

E-Print Network [OSTI]

Magnetism of individual atoms adsorbed on surfaces Harald Brune a,*, Pietro Gambardella b history: Available online 10 February 2009 Keywords: Magnetic impurities Magnetic anisotropy Spin­orbit coupling Dilute magnetic semiconductors Spin excitation spectroscopy Spin-polarized transport Quantized

Brune, Harald

188

Electron Spin Decoherence in Silicon Carbide Nuclear Spin Bath  

E-Print Network [OSTI]

In this paper, we study the electron spin decoherence of single defects in silicon carbide (SiC) nuclear spin bath. We find that, although the natural abundance of $^{29}\\rm{Si}$ ($p_{\\rm{Si}}=4.7\\%$) is about 4 times larger than that of $^{13}{\\rm C}$ ($p_{\\rm{C}}=1.1\\%$), the electron spin coherence time of defect centers in SiC nuclear spin bath in strong magnetic field ($B>300~\\rm{Gauss}$) is longer than that of nitrogen-vacancy (NV) centers in $^{13}{\\rm C}$ nuclear spin bath in diamond. The reason for this counter-intuitive result is the suppression of heteronuclear-spin flip-flop process in finite magnetic field. Our results show that electron spin of defect centers in SiC are excellent candidates for solid state spin qubit in quantum information processing.

Li-Ping Yang; Christian Burk; Mattias Widmann; Sang-Yun Lee; Jörg Wrachtrup; Nan Zhao

2014-09-16T23:59:59.000Z

189

The effects of Co-Ti co-doping on the magnetic, electrical, and magnetodielectric behaviors of M-type barium hexaferrites  

SciTech Connect (OSTI)

Magnetic, electrical and magnetodielectric properties have been studied in Co-Ti co-doped M-type hexaferrite BaCo{sub x}Ti{sub x}Fe{sub 12-2x}O{sub 19} (x = 0 ? 4). With the incorporation of Co-Ti, both their ferromagnetic magnetization and coercivity have been greatly changed. The temperature dependent magnetization curve shows a apparent hump at around 420 K, likely in association with more complicated cycloidal spin ordering, which is closely related to ferroelectric polarization. Interestingly, a significantly enhancement in resistivity (?3 orders in magnitude) can be obtained in co-doped samples (x > 2), which is beneficial for magnetoelectric properties. The magnetoelectric effect were examined by dielectric tunibility under external magnetic field, which shows apparent tunability up to ??3% for sample with x = 2 at 1T magnetic field, further supporting it is a room temperature single phase mutliferroic material.

Guan, Yujie; Lin, Yuanbin; Zou, Liangying; Miao, Qing; Zeng, Min; Gao, Xingsen, E-mail: xingsengao@scnu.edu.cn [Institute for Advanced Materials, South China Normal University, Guangzhou 510006 (China)] [Institute for Advanced Materials, South China Normal University, Guangzhou 510006 (China); Liu, Zhongwu [Department of Metallic Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China)] [Department of Metallic Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Liu, Junming [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)] [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)

2013-12-15T23:59:59.000Z

190

Spin rotation and birefringence effect for a particle in a high energy storage ring and measurement of the real part of the coherent elastic zero-angle scattering amplitude, electric and magnetic polarizabilities  

E-Print Network [OSTI]

In the present paper the equations for the spin evolution of a particle in a storage ring are analyzed considering contributions from the tensor electric and magnetic polarizabilities of the particle. Study of spin rotation and birefringence effect for a particle in a high energy storage ring provides for measurement as the real part of the coherent elastic zero-angle scattering amplitude as well as tensor electric and magnetic polarizabilities. We proposed the method for measurement the real part of the elastic coherent zero-angle scattering amplitude of particles and nuclei in a storage ring by the paramagnetic resonance in the periodical in time nuclear pseudoelectric and pseudomagnetic fields.

V. G. Baryshevsky; A. A. Gurinovich

2005-06-14T23:59:59.000Z

191

Investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al alloy with Ag and Mn additions  

SciTech Connect (OSTI)

The investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al, Cu-11%Al-3%Ag, Cu-11%Al-10%Mn and Cu-11%Al-10%Mn-3%Ag alloys was made using microhardness measurements, differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy, energy dispersion X-ray spectroscopy and magnetic moment change with applied field measurement. The results indicated that the Mn addition changes the phase stability range, the microhardness values and makes undetectable the eutectoid reaction in annealed Cu-11%Al and Cu-11%Al-3%Ag alloys while the presence of Ag does not modify the phase transformation sequence neither microhardness values of the annealed Cu-11%Al and Cu-11%Al-10%Mn alloys, but it increases the magnetic moment of this latter at about 2.7 times and decreases the rates of eutectoid and peritectoid reactions of the former. - Highlights: Black-Right-Pointing-Pointer The microstructure of Cu-Al alloy is modified in the Ag presence. Black-Right-Pointing-Pointer ({alpha} + {gamma}) phase is stabilized down to room temperature when Ag is added to Cu-Al alloy. Black-Right-Pointing-Pointer Ag-rich phase modifies the magnetic characteristics of Cu-Al-Mn alloy.

Silva, R.A.G., E-mail: galdino.ricardo@gmail.com [Departamento de Ciencias Exatas e da Terra-UNIFESP, Diadema-SP (Brazil)] [Departamento de Ciencias Exatas e da Terra-UNIFESP, Diadema-SP (Brazil); Paganotti, A.; Gama, S. [Departamento de Ciencias Exatas e da Terra-UNIFESP, Diadema-SP (Brazil)] [Departamento de Ciencias Exatas e da Terra-UNIFESP, Diadema-SP (Brazil); Adorno, A.T.; Carvalho, T.M.; Santos, C.M.A. [Instituto de Quimica - UNESP, Araraquara-SP (Brazil)] [Instituto de Quimica - UNESP, Araraquara-SP (Brazil)

2013-01-15T23:59:59.000Z

192

Spin squeezing in the Ising model  

Science Journals Connector (OSTI)

We analyze the collective spin noise in interacting spin systems. General expressions are derived for the short-time behavior of spin systems with general spin-spin interactions, and we suggest optimum experimental conditions for the detection of spin squeezing. For Ising models with site-dependent nearest-neighbor interactions, general expressions are presented for the spin squeezing parameter for all times. The reduction of collective spin noise can be used to verify the entangling powers of quantum computer architectures based on interacting spins.

Xiaoguang Wang; Anders Søndberg Sørensen; Klaus Mølmer

2001-10-12T23:59:59.000Z

193

Identification and selection rules of the spin-wave eigen-modes in a normally magnetized nano-pillar  

E-Print Network [OSTI]

effects in the electronic transport properties1 . An elementary device of spintronics consists of two magnetic layers separated by a normal layer. It exhibits the well- known giant magneto-resistance (GMR) effect2,3 , that is, its resistance depends on the relative angle between the magnetic layers. Nowadays

Boyer, Edmond

194

Inhomogeneous magnetism in the doped kagome lattice of LaCuO2.66  

SciTech Connect (OSTI)

The hole-doped kagome lattice of Cu2+ ions in LaCuO2.66 was investigated by nuclear quadrupole resonance (NQR), electron spin resonance (ESR), electrical resistivity, bulk magnetization and specific heat measurements. For temperatures above 180 K, the spin and charge properties show an activated behavior suggestive of a narrow-gap semiconductor. At lower temperatures, the results indicate an insulating ground state which may or may not be charge ordered. While the frustrated spins in remaining patches of the original kagome lattice might not be directly detected here, the observation of coexisting non-magnetic sites, free spins and frozen moments reveals an intrinsically inhomogeneous magnetism. Numerical simulations of a 1/3-diluted kagome lattice rationalize this magnetic state in terms of a heterogeneous distribution of cluster sizes and morphologies near the site-percolation threshold.

Julien, M.-H. [Laboratoire National des Champs Magn´etiques Intenses; Simonet, V [Institut Neel, CNRS-UJF; Canals, B. [Institut Neel, CNRS-UJF; Garlea, Vasile O [ORNL; Bordet, Pierre [Laboratoire of Cristallographie, Grenoble; Darie, Celine [Laboratoire of Cristallographie, Grenoble

2013-01-01T23:59:59.000Z

195

Magnetism  

Science Journals Connector (OSTI)

... dipoles in applied fields". It deals with the classical (Langevin) theory of para-magnetism, anisotropy fields and magnetic measurements. In the next chapter "Atomic structure" the author ... special relevance to ferrites and the inclusion of a quite lengthy discussion of Pauli para-magnetism and of Stoner's treatment of itinerant electron ferromagnetism, though it does much to ...

E. W. LEE

1972-03-31T23:59:59.000Z

196

Characterization of the sp2 bonds network in a-C:H layers with nuclear magnetic resonance, electron energy loss spectroscopy and electron spin resonance  

Science Journals Connector (OSTI)

a-C:H layers prepared at different ion energies have been investigated by several methods including 13C nuclear magnetic resonance (NMR), electron energy loss spectroscopy (EELS) and electron spin resonance (ESR). The sp2 fraction of the samples rose from 27% to about 60 at.% with increasing ion energies from 30 eV to 170 eV. In the EELS spectra of these layers the intensity of the ? ? ?? transition between 4 and 7 eV showed no significant variation. But a shift of the peak is observed from 7 eV to lower energy losses with increasing ion energies indicating an enhanced formation of larger sp2 cluster sizes. This shift is accompanied by a broadening of the energy loss peak, suggesting a broadening of the cluster size distribution. The ESR spectra showed an increase of the spin density by more than one order of magnitude with increasing ion energies. Simultaneously the linewidth of the ESR signal gets narrower. This can also be interpreted as an increasing cluster size from single benzene rings to three and four fused six-fold rings. Hence, the EELS and ESR spectra lead to the same conclusions with respect to the microstructure of the a-C:H network.

R. Kleber; K. Jung; H. Ehrhardt; I. Mühling; K. Breuer; H. Metz; F. Engelke

1991-01-01T23:59:59.000Z

197

2 n -SEMA -a robust solid state nuclear magnetic resonance experiment for measuring heteronuclear dipolar couplings in static oriented systems using effective transverse spin-lock  

Science Journals Connector (OSTI)

Separated local field (SLF) spectroscopy is a powerful technique to measure heteronuclear dipolar couplings. The method provides site-specific dipolar couplings for oriented samples such as membrane proteins oriented in lipid bilayers and liquid crystals. A majority of the SLF techniques utilize the well-known Polarization Inversion Spin Exchange at Magic Angle (PISEMA) pulse scheme which employs spin exchange at the magic angle under Hartmann–Hahn match. Though PISEMA provides a relatively large scaling factor for the heteronuclear dipolar coupling and a better resolution along the dipolar dimension it has a few shortcomings. One of the major problems with PISEMA is that the sequence is very much sensitive to proton carrier offset and the measured dipolar coupling changes dramatically with the change in the carrier frequency. The study presented here focuses on modified PISEMA sequences which are relatively insensitive to proton offsets over a large range. In the proposed sequences the proton magnetization is cycled through two quadrants while the effective field is cycled through either two or four quadrants. The modified sequences have been named as 2 n -SEMA where n represents the number of quadrants the effective field is cycled through. Experiments carried out on a liquid crystal and a single crystal of a model peptide demonstrate the usefulness of the modified sequences. A systematic study under various offsets and Hartmann–Hahn mismatch conditions has been carried out and the performance is compared with PISEMA under similar conditions.

S. Jayanthi; K. V. Ramanathan

2010-01-01T23:59:59.000Z

198

Compaction and sintering behaviors of a Nd-Fe-B permanent magnet alloy  

SciTech Connect (OSTI)

Extensive x-ray diffraction (XRD) and magnetic measurements were done on Nd/sub 15/ Fe/sub 77/ B/sub 8/ magnet alloy green compacts after cold isostatic pressing following a pulsed 2-T field (CIP) and die-pressing under a static 1.2-T perpendicular field (DP1) or parallel field (DP2), and on those after sintering. An alignment factor F, through the calculation of the integrated diffraction intensity ratio of the XRD patterns, was adopted as the effectiveness of magnetic alignment. At the green compact state, DP1 has the best alignment while CIP the worst. However, after sintering the alignment factor was such that CIP>DPI>DP2, the same order as the magnetic properties. Three mechanisms were proposed for the evolution of the alignment factor at different stages of sintering, i.e., that both the appearance of a liquid phase at low temperatures and preferred grain growth at high temperatures enhance F, while recrystallization at intermediate temperatures deteriorates F. CIP results in less-defect green compact, hence less recrystallization, leading to better resultant alignment

Chin, T.; Hung, M.; Tsai, D.; Wu, K.; Chang, W.

1988-11-15T23:59:59.000Z

199

Dynamic switching of the circulation in tapered magnetic nanodisks  

E-Print Network [OSTI]

spin structure of magnetic vortex cores. Science 298, 577 (Magnetic vortex core observation in circular dots of permalloy. Science

Uhlir, V.

2014-01-01T23:59:59.000Z

200

Localized Spins on Graphene  

Science Journals Connector (OSTI)

The problem of a magnetic impurity, atomic or molecular, absorbed on top of a carbon atom in otherwise clean graphene is studied using the numerical renormalization group. The spectral, thermodynamic, and scattering properties of the impurity are described in detail. In the presence of a small magnetic field, the low-energy electronic features of graphene make it possible to inject spin-polarized currents through the impurity using a scanning tunneling microscope. Furthermore, the impurity scattering becomes strongly spin dependent and for a finite impurity concentration it leads to spin-polarized bulk currents and a large magnetoresistance. In gated graphene the impurity spin is Kondo screened at low temperatures. However, at temperatures larger than the Kondo temperature, the anomalous magnetotransport properties are recovered.

P. S. Cornaglia; Gonzalo Usaj; C. A. Balseiro

2009-01-27T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Neutrino magnetic moment in a magnetized plasma  

E-Print Network [OSTI]

The contribution of a magnetized plasma to the neutrino magnetic moment is calculated. It is shown that only part of the additional neutrino energy in magnetized plasma connecting with its spin and magnetic field strength defines the neutrino magnetic moment. It is found that the presence of magnetized plasma does not lead to the considerable increase of the neutrino magnetic moment in contrast to the results presented in literature previously.

N. V. Mikheev; E. N. Narynskaya

2010-11-08T23:59:59.000Z

202

Nuclear-spin noise  

Science Journals Connector (OSTI)

The spectral density of the Nyquist noise current in a tuned circuit coupled to a sample of nuclear spins has been measured at He4 temperatures with a dc SQUID used as a rf amplifier. When the sample is in thermal equilibrium, a dip is observed in the spectral density at the Larmor frequency. For zero spin polarization, on the other hand, a bump in the spectral density is observed. This bump is due to temperature-independent fluctuations in the transverse component of magnetization, and represents spontaneous emission from the spins into the circuit.

Tycho Sleator; Erwin L. Hahn; Claude Hilbert; John Clarke

1985-10-21T23:59:59.000Z

203

Magnetism  

Science Journals Connector (OSTI)

... THIS is a good book, and we are glad to see the subject of magnetism fully treated in a popularly written text-book. It is a second edition of ... of importance, accuracy, and exhaustiveness, places the present treatise, as far as terrestrial magnetism is concerned, much before any similar book with which we are acquainted. The correction ...

JAMES STUART

1872-03-07T23:59:59.000Z

204

Experimental Test of Complementarity by Nuclear Magnetic Resonance Techniques  

E-Print Network [OSTI]

We have tested complementarity for the ensemble-averaged spin states of nuclei $^{13}$C in the molecule of $^{13}$CHCl$_{3}$ by the use of the spin states of another nuclei $^{1}$H as the path marker. It turns out that the wave-particle duality holds when one merely measures the probability density of quantum states, and that the wave- and particle-like behavior is simultaneously observed with the help of measuring populations and coherence in a single nuclear magnetic resonance(NMR) experiment. Effects of path-marking schemes and causes of the appearance and disappearance of the wave behavior are analysed.

Xiwen Zhu; Ximing Fang; Xinhua Peng; Mang Feng; Kelin Gao; Fei Du

2000-11-22T23:59:59.000Z

205

ARPES Provides Direct Evidence of Spin-Wave Coupling  

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

ARPES Provides Direct Evidence ARPES Provides Direct Evidence of Spin-Wave Coupling ARPES Provides Direct Evidence of Spin-Wave Coupling Print Wednesday, 30 March 2005 00:00 The electronic properties of a metal are determined by the dynamical behavior of its conduction electrons. Conventional band theory accounts for the interaction of the electrons with the static ion lattice. However, coupling to further microscopic degrees of freedom can alter the electron dynamics considerably. For example, "conventional" superconductivity emerges as a result of the electrons' interaction with lattice vibrations (phonons). In magnetic materials, coupling with spin waves (magnons) is also expected. Such interactions may contribute to high-temperature superconductivity in novel materials. Unfortunately, lattice vibrations and spin waves have similar energy scales, hindering detailed study. Researchers have taken a new approach in analyzing the electron bands of ferromagnetic iron. Angle-resolved photoemission spectroscopy (ARPES) provides direct spectroscopic evidence of altered electron mass and energy (quasiparticle formation) in a magnetic solid due to coupling with spin waves.

206

Titan's New Build Attracts Magnetic Systems Research Impossible Until Now  

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

Titan's New Build Attracts Magnetic Systems Research Impossible Until Now Titan's New Build Attracts Magnetic Systems Research Impossible Until Now November 01, 2013 Researchers using Titan are studying the behavior of magnetic systems by simulating nickel atoms as they reach their Curie temperature-the threshold between order (right) and disorder (left) when atoms spin into random magnetic directions of fluctuating magnetic strengths, causing the material to lose its magnetism. As simple as magnets seemed during school science lessons (opposites attract, likes repel), improving the performance of magnetic materials and creating new alloys is so complicated Markus Eisenbach, computational scientist at Oak Ridge National Laboratory, has been waiting for a computer that can perform as many as twenty quadrillion calculations per second to

207

Photo-Induced Spin State Switching In [Fe(bpp){sub 2}](NCS){sub 2{center_dot}}2H{sub 2}O  

SciTech Connect (OSTI)

We present the results of our investigation into the effect of irradiation of green light on the high spin <--> low spin transition behavior of the mononuclear iron(II) compound [Fe(bpp){sub 2}](NCS){sub 2{center_dot}}2H{sub 2}O explored with the help of magnetic as well as Moessbauer spectroscopic studies. It has been found that the compound exhibits molecular bistability under irradiation of light due to LIESST effect.

Bhattacharjee, Ashis [Department of Physics, Visva-Bharati University, Santiniketan -731235 (India); Institut fuer Anorganische Chemie und Analytische Chemie, Johannes-Gutenberg Universitaet, D-55099 Mainz (Germany); Goodwin, Harry A. [School of Chemistry, University of New South Wales, UNSW 2052, Sydney (Australia); Guetlich, Philipp [Institut fuer Anorganische Chemie und Analytische Chemie, Johannes-Gutenberg Universitaet, D-55099 Mainz (Germany)

2010-12-01T23:59:59.000Z

208

Ising Chain with a Spin Impurity  

Science Journals Connector (OSTI)

Consider a closed, linear chain of N localized spins (each s=12) with nearest-neighbor Ising interaction. Such a chain, exposed to a uniform external magnetic field, will be called the pure host. Replace a single spin in the pure host by an impurity spin which is also subjected to nearest-neighbor Ising interaction and to the external field. The magnitude of the impurity spin, the magnitude of its magnetic moment, and the magnitude and sign of its interaction with the host are allowed to differ from the corresponding values characterizing the host. For the bulk system (N??, for constant linear density of spins), the thermodynamic properties, such as the impurity magnetization, the (position-dependent) magnetization of the impurity-host system and the impurity-host spin correlation functions, are obtained exactly in terms of conventional, tabulated functions. Numerical results are presented for impurity spins of magnitude S=32,52.

H. Falk

1966-11-04T23:59:59.000Z

209

Effect of electronic reconstruction on cuprate-manganite spin switches.  

SciTech Connect (OSTI)

We examine the anomalous inverse spin switch behavior in La{sub 0.7}Ca{sub 0.3}MnO{sub 3}(LCMO)/YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO)/LCMO trilayers by combined transport studies and polarized neutron reflectometry. Measuring magnetization profiles and magnetoresistance in an in-plane rotating magnetic field, we prove that, contrary to many accepted theoretical scenarios, the relative orientation between the two LCMO's magnetizations is not sufficient to determine the magnetoresistance. Rather the field dependence of magnetoresistance is explained by the interplay between the applied magnetic field and the (exponential tail of the) induced exchange field in YBCO, the latter originating from the electronic reconstruction at the LCMO/YBCO interfaces.

Liu, Y.; Visani, C.; Nemes, N. M.; Fitzsimmons, M. R.; Zhu, L. Y.; Tornos, J.; Zhernenkov, M.; Hoffmann, A.; Leon, C.; Santamaria, J.; te Velthuis, S. G. E. (Materials Science Division); (Universidad Complutense de Madrid); (LANL)

2012-01-01T23:59:59.000Z

210

MagLab - MagLab Dictionary: Electron Magnetic Resonance (Transcript...  

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

an electron has a negative charge. When charged objects spin, they produce magnetism In other words, a spinning electron behaves like a tiny magnet. Indeed, THIS IS the...

211

Field-Induced Spin-Flop in Antiferromagnetic Semiconductors with Commensurate and Incommensurate Magnetic Structures: Li2FeGeS4 (LIGS) and Li2FeSnS4 (LITS)  

Science Journals Connector (OSTI)

Li2FeGeS4 (LIGS) and Li2FeSnS4 (LITS), which are among the first magnetic semiconductors with the wurtz-kesterite structure, exhibit antiferromagnetism with TN ? 6 and 4 K, respectively. Both compounds undergo a conventional metamagnetic transition that ...Divalent ions are directed to specific locations within the structures of the Li2?Fe?IV?S4 diamond-like materials to generate antiferromagnetic ordering. Both compounds undergo a reversible spin-flop transition. Changing the tetravalent ion in these materials alters the bandgaps and magnetic structures. The indirect-gap (Eg = 1.4 eV) semiconductor Li2FeGeS4 has a magnetic structure that is commensurate with the nuclear structure, while Li2FeSnS4 has a direct bandgap (Eg = 1.9 eV) and an incommensurate magnetic structure.

Jacilynn A. Brant; Clarina dela Cruz; Jinlei Yao; Alexios P. Douvalis; Thomas Bakas; Monica Sorescu; Jennifer A. Aitken

2014-11-14T23:59:59.000Z

212

Dynamic spin fluctuations at T?0 in a spin-12 ferromagnetic kagome lattice  

Science Journals Connector (OSTI)

We report magnetization, electron-spin resonance (ESR), and muon-spin relaxation (?SR) measurements on single crystals of the S=1/2 (Cu+2) kagome compound Cu(1,3-benzendicarboxylate). The ?SR is carried to temperatures as low as 45 mK. The spin-Hamiltonian parameters are determined from the analysis of the magnetization and ESR data. We find that this compound has anisotropic ferromagnetic interactions. Nevertheless, no spin freezing is observed even at temperatures two orders of magnitude lower than the coupling constants. In light of this finding, the relation between persistent spin dynamics and spin liquids on kagome lattices is reexamined.

Oren Ofer; Lital Marcipar; V. Ravi Chandra; Snir Gazit; Daniel Podolsky; Daniel P. Arovas; Amit Keren

2014-05-16T23:59:59.000Z

213

E-Print Network 3.0 - application au spin Sample Search Results  

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

the charge and the spin, which are widely used in nowadays electronic devices... . The charge defines the interaction with electric fields, whereas the spin (due to its magnetic...

214

E-Print Network 3.0 - angle field spinning Sample Search Results  

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

a pure spin current was converted into electric current by application of a magnetic field... ). This feature is crucial for spintronic allowing spin manipulation by external...

215

Spin dependent transport properties of Mn-Ga/MgO/Mn-Ga magnetic tunnel junctions with metal(Mg, Co, Cr) insertion layer  

SciTech Connect (OSTI)

We report a first principles theoretical investigation of spin polarized quantum transport in Mn{sub 2}Ga/MgO/Mn{sub 2}Ga and Mn{sub 3}Ga/MgO/Mn{sub 3}Ga magnetic tunneling junctions (MTJs) with the consideration of metal(Mg, Co, Cr) insertion layer effect. By changing the concentration of Mn, our calculation shows a considerable disparity in transport properties: A tunneling magnetoresistance (TMR) ratio of 852% was obtained for Mn{sub 2}Ga-based MTJs, however, only a 5% TMR ratio for Mn{sub 3}Ga-based MTJs. In addition, the influence of insertion layer has been considered in our calculation. We found the Co insertion layer can increase the TMR of Mn{sub 2}Ga-based MTJ to 904%; however, the Cr insertion layer can decrease the TMR by 668%; A negative TMR ratio can be obtained with Mg insertion layer. Our work gives a comprehensive understanding of the influence of different insertion layer in Mn-Ga based MTJs. It is proved that, due to the transmission can be modulated by the interfacial electronic structure of insertion, the magnetoresistance ratio of Mn{sub 2}Ga/MgO/Mn{sub 2}Ga MTJ can be improved by inserting Co layer.

Liang, S. H.; Tao, L. L.; Liu, D. P., E-mail: dpliu@iphy.ac.cn; Han, X. F., E-mail: xfhan@iphy.ac.cn [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Lu, Y. [Institut Jean Lamour, UMR 7198, CNRS-Nancy Université, BP 239, 54506 Vandoeuvre (France)

2014-04-07T23:59:59.000Z

216

Interface defects in SiC power MOSFETs - An electrically detected magnetic resonance study based on spin dependent recombination  

SciTech Connect (OSTI)

This study presents electrically detected magnetic resonance (EDMR) measurements on a silicon carbide (SiC) MOSFET having the structure of a double-diffused silicon MOSFET (DMOS). The resonance pattern of a SiC DMOS was measured by monitoring the change of the recombination current between the source/body and the drain. The amplitude of the response has a maximum when the device is biased in depletion due to the equal concentrations of electrons and holes at the interface resulting in the most efficient recombination. The measured anisotropic g-tensor has axial symmetry with g{sub ?} = 2.0051(4) (B ? c-axis), and g{sub ?} = 2.0029(4) (B? c-axis) and the pattern shows several hyperfine (HF) peaks. We tentatively identify the observed defect as a silicon vacancy located directly at the interface.

Gruber, Gernot [KAI GmbH, Europastrasse 8, 9500 Villach, Austria and Graz University of Technology - Institute of Solid State Physics, Petersgasse 16, 8020 Graz (Austria); Hadley, Peter [Graz University of Technology - Institute of Solid State Physics, Petersgasse 16, 8020 Graz (Austria); Koch, Markus [Graz University of Technology - Institute of Experimental Physics, Petersgasse 16, 8020 Graz (Austria); Peters, Dethard [Infineon Technologies, Schottkystrasse 10, 91058 Erlangen (Germany); Aichinger, Thomas [Infineon Technologies, Siemensstrasse 2, 9500 Villach (Australia)

2014-02-21T23:59:59.000Z

217

Metallic Magnetic Hetrostructures  

E-Print Network [OSTI]

This work studied sputter deposited conventional spin valves (SV) and related structures. In SV layered structures, two ferromagnetic layers are separated by a non-magnetic spacer. Under an external magnetic field, the relative orientation...

Leung, Chi Wah

218

Chemical Magnetism Shouheng Sun, Chairman Semiconductivity,  

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

Chemical Magnetism Shouheng Sun, Chairman Semiconductivity, spin delocalization, and excited states of the single molecule magnets Fe 8 Br 8 and Mn 12 -acetate "invited... D....

219

Magnetism in metal-organic capsules  

E-Print Network [OSTI]

Quantum Spin Chains in Magnetism: Molecules to Materials, J.Magnetism in metal-organic capsules Jerry L. Atwood,* a Euan

Atwood, Jerry L.

2010-01-01T23:59:59.000Z

220

Nuclear spin circular dichroism  

SciTech Connect (OSTI)

Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra.

Vaara, Juha, E-mail: juha.vaara@iki.fi [NMR Research Group, Department of Physics, University of Oulu, P.O. Box 3000, FIN-90014 Oulu (Finland)] [NMR Research Group, Department of Physics, University of Oulu, P.O. Box 3000, FIN-90014 Oulu (Finland); Rizzo, Antonio [Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche (IPCF-CNR), Area della Ricerca, via G. Moruzzi 1, I-56124 Pisa (Italy)] [Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche (IPCF-CNR), Area della Ricerca, via G. Moruzzi 1, I-56124 Pisa (Italy); Kauczor, Joanna; Norman, Patrick [Department of Physics, Chemistry and Biology, Linköping University, S-58183 Linköping (Sweden)] [Department of Physics, Chemistry and Biology, Linköping University, S-58183 Linköping (Sweden); Coriani, Sonia, E-mail: coriani@units.it [Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via L. Giorgieri 1, I-34127 Trieste (Italy)] [Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via L. Giorgieri 1, I-34127 Trieste (Italy)

2014-04-07T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Dy-V magnetic interaction and local structure bias on the complex spin and orbital ordering in Dy1?xTbxVO3 (x=0 and 0.2)  

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

The spin and orbital ordering in Dy1?xTbxVO3 (x=0 and 0.2) was studied by measuring x-ray powder diffraction, magnetization, specific heat, and neutron single-crystal diffraction. The results show that G-OO/C-AF and C-OO/G-AF phases coexist in Dy0.8Tb0.20VO3 in the temperature range 2–60 K, and the volume fraction of each phase is temperature and field dependent. The ordering of Dy moments at T*?=?12 K induces a transition from G-OO/C-AF to a C-OO/G-AF phase. Magnetic fields suppress the long-range order of Dy moments and thus the C-OO/G-AF phase below T*. The polarized moments induced at the Dy sublattice by external magnetic fields couple to the V 3d moments, and this coupling favors the G-OO/C-AF state. Also discussed is the effect of the Dy-V magnetic interaction and local structure distortion on the spin and orbital ordering in Dy1?xTbxVO3.

Yan, J.-Q.; Cao, H. B.; McGuire, M. A.; Ren, Y.; Sales, B. C.; Mandrus, D. G.

2013-06-01T23:59:59.000Z

222

magnets  

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

I I Painless Physics Articles BEAM COOLING August 2, 1996 By Leila Belkora, Office of Public Affairs ACCELERATION August 16, 1996 By Dave Finley, Accelerator Division Head RF August 30, 1996 By Pat Colestock, Accelerator Division FIXED TARGET PHYSICS September 20, 1996 By Peter H. Garbincius, Physics Section FIXED TARGET PHYSICS PART DEUX October 16, 1996 By Peter H. Garbincius, Physics Section and Leila Belkora, Office of Public Affaris CROSS SECTION November 1, 1996 By Doreen Wackeroth, Theoretical Physics Edited by Leila Belkora, Office of Public Affaris MAGNETS PART I November 15, 1996 By Hank Glass, Technical Support Section Edited by Donald Sena, Office of Public Affairs MAGNETS PART II January 10, 1997 By Hank Glass, Technical Support Section Edited by Donald Sena, Office of Public Affairs

223

Fractalization drives crystalline states in a frustrated spin system  

SciTech Connect (OSTI)

The fractalized Hofstadter butterfly energy spectrum predicted for magnetically confined fermions diffracted by a crystal lattice has remained beyond the reach of laboratory-accessible magnetic fields. We find the geometrically frustrated spin system SrCu{sub 2}(BO{sub 3}){sub 2} to provide a sterling demonstration of a system in which bosons confined by a magnetic and lattice potential mimic the behavior of fermions in the extreme quantum limit, giving rise to a sequence of plateaus at all magnetization m{sub z}/M{sub sat} = 1/q ratios 9 {>=} q {>=} 2 and p/q = 2/9 (m{sub sat} is the saturation magnetization) in magnetic fields up to 85 T and temperatures down to 29 mK, within the sequence of previously identified plateaus at 1/8, 1/4, and 1/3 of the saturated magnetization. We identify this hierarchy of plateaus as a consequence of confined bosons in SrCu{sub 2}(BO{sub 3}){sub 2} mimicking the high magnetic field fractalization predicted by the Hofstadter butterfly for fermionic systems. Such an experimental realization of the Hofstadter problem for interacting fermions has not been previously achieved in real materials, given the unachievably high magnetic flux densities or large lattice periods required. By a theoretical treatment that includes short-range repulsion in the Hofstadter treatment, stripe-like spin density-modulated phases are revealed in SrCu{sub 2}(BO{sub 3}){sub 2} as emergent from a fluidic fractal spectrum.

Harrison, Neil [Los Alamos National Laboratory; Sengupta, Pinaki [Los Alamos National Laboratory; Batista, Cristian [Los Alamos National Laboratory; Sebastian, Suchitra [UNIV OF CAMBRIDGE

2008-01-01T23:59:59.000Z

224

MOTT INSULATORS, SPIN LIQUIDS AND QUANTUM DISORDERED SUPERCONDUCTIVITY  

E-Print Network [OSTI]

COURSE 7 MOTT INSULATORS, SPIN LIQUIDS AND QUANTUM DISORDERED SUPERCONDUCTIVITY MATTHEW P.A. FISHER insulators and quantum magnetism 583 3.1 Spin models and quantum magnetism . . . . . . . . . . . . . . . . . . . . . . . . . . . . 637 #12;MOTT INSULATORS, SPIN LIQUIDS AND QUANTUM DISORDERED SUPERCONDUCTIVITY Matthew P.A. Fisher

225

Dynamical properties of a crystalline rare-earth boron cluster spin-glass system  

Science Journals Connector (OSTI)

Dynamical properties of the magnetic B12 cluster compound HoB22C2N were investigated. HoB22C2N is taken to be representative of the class of trigonal and rhombohedral B12 cluster compounds which were found to exhibit spin-glass behavior as measured by dc superconducting quantum interference device magnetometer and specific-heat measurements. These are examples of magnetic glassiness being observed in rare earth boron-rich crystalline cluster compounds. Well defined maxima in the in-phase linear ac susceptibility ?? curves were observed, indicative of the spin-glass transition. Strong frequency dependence of the cusp temperature Tf was found. The dependence of Tf could not be analyzed satisfactorily by the dynamical scaling theory of a three-dimensional spin glass. A more detailed investigation of the behavior of relaxation times by Cole-Cole analysis showed that the behavior in HoB22C2N is different from the simple blocking of a superparamagnetic system, because of the temperature dependence of the parameter ? representing the width of the relaxation-time distribution function g(?). The median relaxation time was also determined and the data were found to be described well in terms of a generalized Arrhenius law ln ??T-2.5. These results indicate that HoB22C2N is a two-dimensional spin-glass system, which supports what has been speculated previously.

Takao Mori and Hiroaki Mamiya

2003-12-18T23:59:59.000Z

226

A study of the order-disorder, solid-solid phase transition of (+)-camphor using nuclear magnetic resonance with cross-polarization and magic-angle spinning  

E-Print Network [OSTI]

Parameters in the Rotating Frame . 52 a. Proton Spin-Lattice Relaxation in the Rotating Frame. . . 52 b. T and Contact Time. CH c. Carbon Spin-Lattice Relaxation in the Rotating Frame. 53 54 d. Adiabatic Demagnetization in the Rotating Frame. 56 2... the orientation of the magic-angle sample spinning with respect to B 0 Figure 1. 9. Illustrates the pulse sequence used for cross-polarization. S. L. represents the proton spin-lock time. . 39 . 45 Figure 1. 10. Depicts the cross-polarization process as a...

Crook, Russell Allan

2012-06-07T23:59:59.000Z

227

Low-temperature magnetic characterization of optimum and etch-damaged in-plane magnetic tunnel junctions  

SciTech Connect (OSTI)

We describe low-temperature characterization of magnetic tunnel junctions (MTJs) patterned by reactive ion etching for spin-transfer-torque magnetic random access memory. Magnetotransport measurements of typical MTJs show increasing tunneling magnetoresistance (TMR) and larger coercive fields as temperature is decreased down to 10 K. However, MTJs selected from the high-resistance population of an MTJ array exhibit stable intermediate magnetic states when measured at low temperature and show TMR roll-off below 100 K. These non-ideal low-temperature behaviors arise from edge damage during the etch process and can have negative impacts on thermal stability of the MTJs.

Kan, Jimmy J.; Gottwald, Matthias; Fullerton, Eric E. [Center for Magnetic Recording Research, University of California, San Diego, La Jolla, California 92093 (United States)] [Center for Magnetic Recording Research, University of California, San Diego, La Jolla, California 92093 (United States); Lee, Kangho; Kang, Seung H. [Advanced Technology, Qualcomm, Inc., San Diego, California 92121 (United States)] [Advanced Technology, Qualcomm, Inc., San Diego, California 92121 (United States)

2013-09-21T23:59:59.000Z

228

An accreting low magnetic field magnetar for the ultraluminous X-ray source in M82  

E-Print Network [OSTI]

One ultraluminous X-ray source in M82 is identified as an accreting neutron recently (named as NuSTAR J095551+6940.8). It has a super-Eddington luminosity and is spinning up. For an aged magnetar, it is more likely to be a low magnetic field magnetar. An accreting low magnetic field magnetar may explain both the super-Eddington luminosity and the rotational behaviors. Considering the effect of beaming, the spin-up rate is understandable using the traditional form of accretion torque. The transient nature, spectral properties, theoretical period range are discussed. Three observational appearances of accreting magnetars are summarized.

Tong, H

2014-01-01T23:59:59.000Z

229

Mechanism and assessment of spin transfer torque (STT) based memory  

E-Print Network [OSTI]

When a sufficient current density passes through the MTJ, the spin-polarized current will exert a spin transfer torque to switch the magnetization of the free layer. This is the fundamental of the novel write mechanism in ...

Loh, Iong Ying

2009-01-01T23:59:59.000Z

230

Magnetic structure of free iron clusters compared to iron crystal surfaces  

Science Journals Connector (OSTI)

Electronic and magnetic properties of free Fe clusters of 9 to 89 atoms are investigated theoretically within an ab initio fully relativistic framework and compared to results of crystal surfaces. It is found that the local spin magnetic moments ?spin and the orbital magnetic moments ?orb are enhanced for atoms close to the surface of a Fe cluster. The corresponding Friedel-like oscillations in the depth profiles of ?spin and ?orb are more pronounced for clusters than for crystal surfaces. The ?spin in clusters and at crystal surfaces turned out to depend linearly on the effective coordination number Neff. This empirical ?spin-Neff inter-relationship is able to account for some features of the experimentally measured dependence of the magnetic moment of free Fe clusters on the cluster size. The spin-polarized density of states (DOS’s) for atoms in clusters is characterized by sharp atomiclike peaks and substantially differs from the DOS in the bulk. The width of the local valence band gets more narrow if one is moving from the center of the cluster to its surface. The DOS averaged over all atoms in a cluster converges to the bulk behavior more quickly with cluster size than the DOS of the central atoms of these clusters.

O. Šipr, M. Košuth, and H. Ebert

2004-11-15T23:59:59.000Z

231

Spinning angle optical calibration apparatus  

DOE Patents [OSTI]

An optical calibration apparatus is provided for calibrating and reproducing spinning angles in cross-polarization, nuclear magnetic resonance spectroscopy. An illuminated magnifying apparatus enables optical setting an accurate reproducing of spinning "magic angles" in cross-polarization, nuclear magnetic resonance spectroscopy experiments. A reference mark scribed on an edge of a spinning angle test sample holder is illuminated by a light source and viewed through a magnifying scope. When the "magic angle" of a sample material used as a standard is attained by varying the angular position of the sample holder, the coordinate position of the reference mark relative to a graduation or graduations on a reticle in the magnifying scope is noted. Thereafter, the spinning "magic angle" of a test material having similar nuclear properties to the standard is attained by returning the sample holder back to the originally noted coordinate position.

Beer, Stephen K. (Morgantown, WV); Pratt, II, Harold R. (Morgantown, WV)

1991-01-01T23:59:59.000Z

232

Complex magnetic behavior of the sawtooth Fe chains in Rb2Fe2O(AsO4)2  

SciTech Connect (OSTI)

Results of magnetic eld and temperature dependent neutron diraction and magnetization mea- surements on oxy-arsenate Rb2Fe2O(AsO4)2 are reported. The crystal structure of this compound contains pseudo-one-dimensional [Fe2O6] sawtooth-like chains, formed by corner sharing isosce- les triangles of Fe3+ ions occupying two nonequivalent crystallographic sites. The chains extend innitely along the crystallographic b-axis and are structurally conned from one another via dia- magnetic (AsO4)3- units along the a-axis, and Rb+ cations along the c-axis direction. Neutron diraction measurements indicate the onset of a long range antiferromagnetic order below approxi- mately 25 K. The magnetic structure consists of ferrimagnetic chains which are antiferromagnetically coupled with each other. Within each chain, one of the two Fe sites carries a moment which lies along the b-axis, while the second site bears a canted moment in the opposite direction. Exter- nally applied magnetic eld induces a transition to a ferrimagnetic state, in which the coupling between the sawtooth chains becomes ferromagnetic. Magnetization measurements performed on optically-aligned single crystals reveal evidence for an uncompensated magnetization at low mag- netic elds that could emerge from to a phase-segregated state with ferrimagnetic inclusions or from antiferromagnetic domain walls. The observed magnetic states and the competition between them is expected to arise from strongly frustrated interactions within the sawtooth chains and relatively weak coupling between them.

Garlea, Vasile O [ORNL] [ORNL; Sanjeewa, Liurukara D. [Clemson University] [Clemson University; McGuire, Michael A [ORNL] [ORNL; Kumar, Pramod [Indian Institute of Information Technology] [Indian Institute of Information Technology; Sulejmanovic, Dino [Clemson University] [Clemson University; Hwu, Shiou-Jyh [Clemson University] [Clemson University

2014-01-01T23:59:59.000Z

233

Role of Er3+ ion in the formation of the ErFeO3 magnetic properties in the region of spin-reorientation phase transition  

Science Journals Connector (OSTI)

The 90° reorientation of Er3+ spins in ErFeO3 have been directly observed using optical spectroscopy. The peculiarities of the absorption spectrum of ErFeO3 in the region of the 4 I ...

A. I. Belyaeva; K. V. Baranova

2009-08-01T23:59:59.000Z

234

Unconventional temperature enhanced magnetism in iron telluride  

SciTech Connect (OSTI)

Discoveries of copper and iron-based high-temperature superconductors (HTSC)1-2 have challenged our views of superconductivity and magnetism. Contrary to the pre-existing view that magnetism, which typically involves localized electrons, and superconductivity, which requires freely-propagating itinerant electrons, are mutually exclusive, antiferromagnetic phases were found in all HTSC parent materials3,4. Moreover, highly energetic magnetic fluctuations, discovered in HTSC by inelastic neutron scattering (INS) 5,6, are now widely believed to be vital for the superconductivity 7-10. In two competing scenarios, they either originate from local atomic spins11, or are a property of cooperative spin-density-wave (SDW) behavior of conduction electrons 12,13. Both assume clear partition into localized electrons, giving rise to local spins, and itinerant ones, occupying well-defined, rigid conduction bands. Here, by performing an INS study of spin dynamics in iron telluride, a parent material of one of the iron-based HTSC families, we have discovered that this very assumption fails, and that conduction and localized electrons are fundamentally entangled. In the temperature range relevant for the superconductivity we observe a remarkable redistribution of magnetism between the two groups of electrons. The effective spin per Fe at T 10 K, in the2 antiferromagnetic phase, corresponds to S 1, consistent with the recent analyses that emphasize importance of Hund s intra-atomic exchange15-16. However, it grows to S 3/2 in the disordered phase, a result that profoundly challenges the picture of rigid bands, broadly accepted for HTSC.

Zalinznyak, I. [Brookhaven National Laboratory (BNL); Xu, Zhijun [ORNL; Tranquada, John M. [Brookhaven National Laboratory (BNL); Gu, G. D. [Brookhaven National Laboratory (BNL); Tsvelik, A. [Brookhaven National Laboratory (BNL); Stone, Matthew B [ORNL

2011-01-01T23:59:59.000Z

235

Directed Assembly of Single-Molecule and Single-Chain Magnets: From Mononuclear High-Spin Iron(II) Complexes to Cyano-Bridged Chain Compounds  

E-Print Network [OSTI]

new cyano-bridged single-molecule and single-chain magnetsand have come to be known as single- molecule magnets. Thisin part because single- molecule magnets could potentially

Harris, Thomas

2010-01-01T23:59:59.000Z

236

Novel bias-field-free spin transfer oscillator  

SciTech Connect (OSTI)

Two versions of magnetic field free spin torque oscillators with in- and out-of-plane spin polarizers are proposed. The field free spin torque oscillators comprise two spin valve stacks with a common free magnetic layer featuring an out-of-plane anisotropy. Their operation frequencies are controlled by the dimensions of the free layer and can also be tuned by the applied currents. Large and stable magnetization precessional motion of the whole shared free layer for both oscillators are obtained. The structure with in-plane polarizers allows more efficient microwave power extraction of the large in-plane magnetization precession of the free layer.

Windbacher, Thomas, E-mail: windbacher@iue.tuwien.ac.at; Makarov, Alexander; Mahmoudi, Hiwa; Sverdlov, Viktor; Selberherr, Siegfried [Institute for Microelectronics, TU Wien, Gußhausstraße 27–29/E360, A-1040 Wien (Austria)

2014-05-07T23:59:59.000Z

237

Crystal-Field Splitting and Giant Negative Magnetization in  

SciTech Connect (OSTI)

Bimetallic oxalates are a class of layered organic magnets with transi- tion metals M(II) and M'(III) coupled by oxalate molecules in an open honeycomb structure. Of particular interest are the Fe(II)Fe(III) bimetal- lic compounds, which are ferrimagnetically ordered below a transition temperature that ranges from 30 to 48 K, depending on the cation that separates the layers. In small magnetic fields, several of these compounds exhibit giant negative magnetization below a compensation temperature of roughly 2/3 Tc. By studying the behavior of the Kramer's doublet ground state produced by the crystal-field splitting and constructing a reduced Hamiltonian that includes both exchange and spin-orbit and in- teractions, we can explain all of the important behavior of this class of materials: the stability of magnetic order in two dimensions and the existence of magnetic compensation in samples with high transition tem- peratures. We also provide several new predictions for the spin-wave gap and the optical flipping of the magnetic moment.

Fishman, Randy Scott [ORNL; Reboredo, Fernando A [ORNL

2007-01-01T23:59:59.000Z

238

Pressure driven spin crossover and isostructural phase transition in LaFeO{sub 3}  

SciTech Connect (OSTI)

We have studied the behavior of LaFeO{sub 3} under pressure (P) using density functional theory (DFT) and atomistic simulations. Ground state structural properties of LaFeO{sub 3} are correctly described by atomistic simulations. The effect of high pressure shows that there is an isotropic compression up to 100?GPa. However, DFT calculations show that within pressure range 0?spin magnetic phase transition is observed, which is accompanied by 6.9% volume collapse of LaFeO{sub 3} unit cell, while retaining the ground state orthorhombic crystal structure, i.e., isostructural phase transition. Furthermore, the band gap is closed leading insulator to metal transition. This differing behavior observed by the two techniques can be attributed to the omission of magnetic effects in static simulations. The simultaneous magnetic, electrical, and structural (volume collapse) phase transitions of LaFeO{sub 3} under compression as revealed by DFT calculations corroborate experimental findings. From these results, we can elaborate the mechanism of phase transition in LaFeO{sub 3}: increasing crystal field induces a high spin to low spin transition, which in turn drives the electrical transitions and volume collapse.

Javaid, Saqib [EMMG, Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); National Centre of Physics, Islamabad (Pakistan); Javed Akhtar, M., E-mail: javedakhtar6@gmail.com; Younas, Muhammad [EMMG, Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Ahmad, Irfan [EMMG, Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); DMME, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad (Pakistan); Shah, Shafqat H. [Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Ahmad, Iftikhar [Department of Physics, University of Malakand, Chakdara (Pakistan)

2013-12-28T23:59:59.000Z

239

Polytype control of spin qubits in silicon carbide  

E-Print Network [OSTI]

Crystal defects can confine isolated electronic spins and are promising candidates for solid-state quantum information. Alongside research focusing on nitrogen vacancy centers in diamond, an alternative strategy seeks to identify new spin systems with an expanded set of technological capabilities, a materials driven approach that could ultimately lead to "designer" spins with tailored properties. Here, we show that the 4H, 6H and 3C polytypes of SiC all host coherent and optically addressable defect spin states, including spins in all three with room-temperature quantum coherence. The prevalence of this spin coherence shows that crystal polymorphism can be a degree of freedom for engineering spin qubits. Long spin coherence times allow us to use double electron-electron resonance to measure magnetic dipole interactions between spin ensembles in inequivalent lattice sites of the same crystal. Together with the distinct optical and spin transition energies of such inequivalent spins, these interactions provide ...

Falk, Abram L; Calusine, Greg; Koehl, William F; Dobrovitski, Viatcheslav V; Politi, Alberto; Zorman, Christian A; Feng, Philip X -L; Awschalom, David D; 10.1038/ncomms2854

2013-01-01T23:59:59.000Z

240

Deuteron spin-lattice relaxation for HD in solid argon  

Science Journals Connector (OSTI)

Measurements, using 55-MHz deuteron magnetic resonance (DMR), are reported of deuteron spin-lattice relaxation times for HD in solid argon at concentrations of 300–1100 ppm over the temperature range of 10–70 K. The relaxation times increase rapidly, from 10 to 4000 sec, as the temperature is reduced and are independent of the sample’s para-D2 concentration. Comparisons of deuteron spin-lattice relaxation times for HD in solid argon are made with previously reported relaxation times for solid HD–n-D2 mixtures and for ortho-H2 and para-D2 in solid argon. The very different relaxation behavior for HD can be understood because it is an asymmetric molecule. The lack of exchange symmetry results in an increasing probability of the molecule being in a J=0 rotational state as the temperature is reduced. Nuclear spin-lattice relaxation in HD arises from phonon-induced ?mJ transitions for those molecules in the J=1 states. A theory is presented to calculate the nuclear spin-lattice relaxation rate (1/T1) in terms of a molecular decay rate (?) that arises from ?mJ or ?J transitions. The decay rate ? as a function of temperature is determined from the relaxation data. It is found that the asymmetric rotor HD molecules have a coupling to the lattice phonons that is much stronger than for ortho-H2 and para-D2.

Joseph Ganem; Peter A. Fedders; R. E. Norberg

1993-02-01T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Electrically driven spin resonance in silicon carbide color centers  

E-Print Network [OSTI]

We demonstrate that the spin of optically addressable point defects can be coherently driven with AC electric fields. Based on magnetic-dipole forbidden spin transitions, this scheme enables spatially confined spin control, the imaging of high-frequency electric fields, and the characterization of defect spin multiplicity. While we control defects in SiC, these methods apply to spin systems in many semiconductors, including the nitrogen-vacancy center in diamond. Electrically driven spin resonance offers a viable route towards scalable quantum control of electron spins in a dense array.

P. V. Klimov; A. L. Falk; B. B. Buckley; D. D. Awschalom

2013-10-17T23:59:59.000Z

242

Dynamics of spin-flip photon-assisted tunneling  

Science Journals Connector (OSTI)

We present time-resolved measurements of spin-flip photon-assisted tunneling and spin-flip relaxation in a doubly occupied double quantum dot. The photon-assisted excitation rate as a function of magnetic field indicates that spin-orbit coupling is the dominant mechanism behind the spin-flip under the present conditions. We are able to extract the resulting effective “spin-flip tunneling” energy, which is found to be three orders of magnitude smaller than the regular spin-conserving tunneling energy. We also measure the relaxation and dephasing times of a qubit formed out of two two-electron states with different spin and charge configurations.

F. R. Braakman; J. Danon; L. R. Schreiber; W. Wegscheider; L. M. K. Vandersypen

2014-02-18T23:59:59.000Z

243

Noble gas magnetic resonator  

DOE Patents [OSTI]

Precise measurements of a precessional rate of noble gas in a magnetic field is obtained by constraining the time averaged direction of the spins of a stimulating alkali gas to lie in a plane transverse to the magnetic field. In this way, the magnetic field of the alkali gas does not provide a net contribution to the precessional rate of the noble gas.

Walker, Thad Gilbert; Lancor, Brian Robert; Wyllie, Robert

2014-04-15T23:59:59.000Z

244

Magnetism in transition metals  

Science Journals Connector (OSTI)

By using the Hubbard tight-binding-type Hamiltonian and the cluster Bethe-lattice approximation we calculate for Fe the Curie temperature TC=2250 K and the temperature dependence of the magnetic moments and the magnetization. Moreover, we show how previous theories for itinerant magnets may be extended to include short-range spin correlations.

J. L. Morán-López; K. H. Bennemann; M. Avignon

1981-06-01T23:59:59.000Z

245

Magnetic and electronic properties of NpCo2: Evidence for long-range magnetic order  

Science Journals Connector (OSTI)

The magnetic and electronic properties of the cubic Laves phase intermetallic compound NpCo2 have been investigated by magnetization, specific heat, and electrical resistivity measurements. Magnetization data confirm previous results, i.e., an antiferromagneticlike order at 12.5 K and a metamagnetic transition at Bm ? 4.3 T at 3 K with a saturation moment of ?0.6 ?B. Although extensive neutron diffraction studies failed to establish the nature of the antiferromagnetic order, its occurrence is confirmed by specific heat measurements that also highlight the presence of magnetic fluctuations suppressed by the application of an external field larger than Bm. The observed high value of the electronic specific heat, ?0 ? 330 mJ/mol?K2 as T ? 0, and the minute magnetic entropy, Fermi liquid behavior at low temperature. The electronic structure of NpCo2 was examined theoretically and compared to experimental data. Local spin density approximation (LSDA) calculations show that this material is close to a magnetic instability and that ferromagnetic alignment of the Np moments is the most stable. LSDA+U calculations in the fully localized limit with U = 0 give reasonable agreement with the experimental Np moment value and their orbital and spin contributions.

J. P. Sanchez; J.-C. Griveau; P. Javorsky; E. Colineau; R. Eloirdi; P. Boulet; J. Rebizant; F. Wastin; A. B. Shick; R. Caciuffo

2013-04-10T23:59:59.000Z

246

Theory of Toeplitz Determinants and the Spin Correlations of the Two-Dimensional Ising Model. IV  

Science Journals Connector (OSTI)

We consider the rectangular Ising model on a half-plane of infinite extent and study some of the consequences connected with the presence of the boundary. Only the spins on the boundary row are allowed to interact with a magnetic field H. The method of Pfaffians is employed to obtain exact expressions for the partition function. It is found that the free energy is the sum of two terms, one of which is independent of H and proportional to the total number of lattice sites, while the other depends on H and is proportional to the number of lattice sites on the boundary. This separation makes it possible to define various thermodynamic quantities associated with the boundary. In particular, the boundary magnetization is shown to be discontinuous, in the ferromagnetic case, at zero magnetic field for temperatures below the bulk critical temperature Tc. This discontinuity, which is the spontaneous boundary magnetization, goes to zero as (1-TTc)12 as T?Tc-. For T=Tc, the discontinuity is of course absent, and the boundary magnetization behaves as -HlnH for small H. The boundary susceptibility at zero magnetic field in the ferromagnetic case exhibits a logarithmic singularity at T=Tc, both above and below transition. An interesting feature is that the ferromagnetic boundary magnetization, although discontinuous for Tspin. The correlation function for two spins, both on the boundary row, is also obtained exactly and its asymptotic behavior is given. Finally, we derive an expression for the magnetization in any row and explicitly evaluate it for the second row, i.e., the row next to the boundary.

Barry M. McCoy and Tai Tsun Wu

1967-10-10T23:59:59.000Z

247

LaSrVO4: a candidate for the spin-orbital liquid state  

SciTech Connect (OSTI)

A layered perovskite LaSrVO4 was studied by neutron diraction, pair distribution function measurement using synchrotron x-ray, susceptibility and specific heat measurements, and first-principles calculation. The results show (i) a weak structural distortion around 100 K with the existence of orbital fluctuations both above and below it; (ii) the absence of the long range magnetic ordering down to 0.35 K but the appearance of a short range magnetic ordering around 11 K with a T2 behavior of the specic heat below it. Meanwhile, the calculation based on the density functional theory predicts a magnetic ordered ground state. All facts indicate a melting of the magnetic ordering due to the orbital fluctuations in LaSrVO4, which makes it a rare candidate for the spin-orbital liquid state related to t2g orbitals.

Dun, Z. L. [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK); Garlea, Vasile O [ORNL] [ORNL; Ren, Y. [Argonne National Laboratory (ANL)] [Argonne National Laboratory (ANL); Choi, E. [National High Magnetic Field Laboratory (Magnet Lab), Florida] [National High Magnetic Field Laboratory (Magnet Lab), Florida; Zhang, H. M. [Southeast University, Nanjing, China] [Southeast University, Nanjing, China; Dong, S. [Southeast University, Nanjing, China] [Southeast University, Nanjing, China; Zhou, H. D. [University of Tennessee (UT)] [University of Tennessee (UT)

2014-01-01T23:59:59.000Z

248

Neutron Scattering and Ordering of Nuclear Spins  

Science Journals Connector (OSTI)

The ordering of nuclear spins takes place at extremely low temperatures because of the weakness of the interactions between their magnetic moments. Neutron scattering is the traditional and unique method to ... (...

M. Steiner

2004-06-01T23:59:59.000Z

249

Storage rings for spin-polarized hydrogen  

Science Journals Connector (OSTI)

A strong-focusing storage ring is proposed for the long-term magnetic confinement of a collisional gas of neutral spin-polarized hydrogen atoms in the |a? and |b? hyperfine states. The...

Thompson, D; Lovelace, R V E; Lee, D M

1989-01-01T23:59:59.000Z

250

Frustrated quantum magnet the pyrochlore structure consists of corner  

E-Print Network [OSTI]

to exotic magnetic ground states. Quantum Spin Ice: Pyrochlore Quantum Magnet Tb2Ti2O7 at Ultra to determine the nature of magnetic ordering -if any- as a function of applied magnetic field using the ultra magnetization plateau below 50 mK (Fig. 2), as predicted for a single-tetrahedron four -spin model. This new

McQuade, D. Tyler

251

Pseudo-spin paramagnetism in graphene  

SciTech Connect (OSTI)

We calculate the orbital diamagnetic susceptibility of monolayer graphene with an energy gap. The valley pseudo-spin produces paramagnetic susceptibility analogous to contribution from real spin, and explains the origin of a singular orbital magnetism at Dirac point of monolayer graphene.

Koshino, Mikito; Ando, Tsuneya [Department of Physics, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)

2011-12-23T23:59:59.000Z

252

Single-parameter spin-pumping in driven metallic rings with spin-orbit coupling  

SciTech Connect (OSTI)

We consider the generation of a pure spin-current at zero bias voltage with a single time-dependent potential. To such end we study a device made of a mesoscopic ring connected to electrodes and clarify the interplay between a magnetic flux, spin-orbit coupling, and non-adiabatic driving in the production of a spin and electrical current. By using Floquet theory, we show that the generated spin to charge current ratio can be controlled by tuning the spin-orbit coupling.

Ramos, J. P.; Apel, V. M. [Departamento de Física, Universidad Católica del Norte, Angamos 0610, Casilla 1280, Antofagasta (Chile); Foa Torres, L. E. F. [Instituto de Física Enrique Gaviola (CONICET) and FaMAF, Universidad Nacional de Córdoba, Ciudad Universitaria 5000, Córdoba (Argentina); Orellana, P. A. [Departamento de Física, Universidad Técnica Federico Santa María, Avenida Vicuña Mackenna 3939, San Joaquin, Santiago (Chile)

2014-03-28T23:59:59.000Z

253

Calculation of geometric phases in electric dipole searches with trapped spin-1/2 particles based on direct solution of the Schrödinger equation  

Science Journals Connector (OSTI)

Pendlebury etal. [Phys. Rev. A 70, 032102 (2004)] were the first to investigate the role of geometric phases in searches for an electric dipole moment (EDM) of elementary particles based on Ramsey-separated oscillatory field magnetic resonance with trapped ultracold neutrons and comagnetometer atoms. Their work was based on the Bloch equation and later work using the density matrix corroborated the results and extended the scope to describe the dynamics of spins in general fields and in bounded geometries. We solve the Schrödinger equation directly for cylindrical trap geometry and obtain a full description of EDM-relevant spin behavior in general fields, including the short-time transients and vertical spin oscillation in the entire range of particle velocities. We apply this method to general macroscopic fields and to the field of a microscopic magnetic dipole.

A. Steyerl; C. Kaufman; G. Müller; S. S. Malik; A. M. Desai; R. Golub

2014-05-22T23:59:59.000Z

254

Calculation of geometric phases in electric dipole searches with trapped spin-1/2 particles based on direct solution of the Schrödinger equation  

E-Print Network [OSTI]

Pendlebury $\\textit{et al.}$ [Phys. Rev. A $\\textbf{70}$, 032102 (2004)] were the first to investigate the role of geometric phases in searches for an electric dipole moment (EDM) of elementary particles based on Ramsey-separated oscillatory field magnetic resonance with trapped ultracold neutrons and comagnetometer atoms. Their work was based on the Bloch equation and later work using the density matrix corroborated the results and extended the scope to describe the dynamics of spins in general fields and in bounded geometries. We solve the Schr\\"odinger equation directly for cylindrical trap geometry and obtain a full description of EDM-relevant spin behavior in general fields, including the short-time transients and vertical spin oscillation in the entire range of particle velocities. We apply this method to general macroscopic fields and to the field of a microscopic magnetic dipole.

A. Steyerl; C. Kaufman; G. Müller; S. S. Malik; A. M. Desai; R. Golub

2014-05-23T23:59:59.000Z

255

Symmetry and cluster magnetism  

Science Journals Connector (OSTI)

Three possible isomers of 13-atom iron clusters are studied using local-density-functional methods that allow the spin of the cluster to be determined self-consistently. The ground state is the icosahedral structure. It has the greatest magnetic moment because of increased symmetry-required orbital degeneracy for electrons of different spins.

Brett I. Dunlap

1990-05-15T23:59:59.000Z

256

Optically Detected Magnetic Resonance Studies on ?-conjugated semiconductor systems  

SciTech Connect (OSTI)

Optically Detected Magnetic Resonance (ODMR) techniques were used to investigate the dynamics of excitons and charge carriers in ?-conjugated organic semiconductors. Degradation behavior of the negative spin-1/2 electroluminescence-detected magnetic resonance (ELDMR) was observed in Alq3 devices. The increase in the resonance amplitude implies an increasing bipolaron formation during degradation, which might be the result of growth of charge traps in the device. The same behavior of the negative spin-1/2 ELDMR was observed in 2wt% Rubrene doped Tris(8-hydroxyquinolinato)aluminium (Alq3) devices. However, with increasing injection current, a positive spin-1/2 ELDMR, together with positive spin 1 triplet powder patterns at {delta}m{sub S}={+-}1 and {delta}m{sub S}={+-}2, emerges. Due to the similarities in the frequency dependences of single and double modulated ELDMR and the photoluminescence-detected magnetic resonance (PLDMR) results in poly[2-methoxy-5-(2 -ethyl-hexyloxy)-1,4-phenyl ene vinylene] (MEH-PPV) films, the mechanism for this positive spin-1/2 ELDMR was assigned to enhanced triplet-polaron quenching under resonance conditions. The ELDMR in rubrene doped Alq3 devices provides a path to investigate charge distribution in the device under operational conditions. Combining the results of several devices with different carrier blocking properties and the results from transient EL, it was concluded trions not only exist near buffer layer but also exist in the electron transport layer. This TPQ model can also be used to explain the positive spin-1/2 PLDMR in poly(3-hexylthiophene) (P3HT) films at low temperature and in MEH-PPV films at various temperatures up to room temperature. Through quantitative analysis, TE-polaron quenching (TPQ) model is shown having the ability to explain most behaviors of the positive spin-1/2 resonance. Photocurrent detected magnetic resonance (PCDMR) studies on MEH-PPV devices revealed a novel transient resonance signal. The signal may originate from the higher concentration of deep traps near cathode. A quantitative analysis based on this assumption was carried out and found to be consistent with the experimental results.

Chen, Ying

2011-12-06T23:59:59.000Z

257

Nuclear Spin Thermometry Below 1 $^\\circ$K  

Science Journals Connector (OSTI)

23 March 1965 research-article Nuclear Spin Thermometry Below 1 K R. E. Walstedt E. L...consists of measuring the magnetization of a system of nuclear spins by means of pulsed nuclear magnetic resonance. Such a thermometer is useful...

1965-01-01T23:59:59.000Z

258

Free Energy of Electrons in Metals with Magnetic and Electric Polarizations. II: Dielectric Constant and Spin Susceptibilities in the Ferromagnetic State  

Science Journals Connector (OSTI)

......Theoretical Physics February 1970 research-article Articles Free Energy of Electrons in Metals with Magnetic and Electric Polarizations...calculation and the Hartree-Fock approximation, the free energy of electrons in metals is expanded as a power series......

Ichiro Takahashi; Masao Shimizu

1970-02-01T23:59:59.000Z

259

Dynamic control of spin wave spectra using spin-polarized currents  

SciTech Connect (OSTI)

We describe a method of controlling the spin wave spectra dynamically in a uniform nanostripe waveguide through spin-polarized currents. A stable periodic magnetization structure is observed when the current flows vertically through the center of nanostripe waveguide. After being excited, the spin wave is transmitted at the sides of the waveguide. Numerical simulations of spin-wave transmission and dispersion curves reveal a single, pronounced band gap. Moreover, the periodic magnetization structure can be turned on and off by the spin-polarized current. The switching process from full rejection to full transmission takes place within less than 3?ns. Thus, this type magnonic waveguide can be utilized for low-dissipation spin wave based filters.

Wang, Qi; Zhang, Huaiwu, E-mail: hwzhang@uestc.edu.cn; Tang, Xiaoli; Bai, Feiming; Zhong, Zhiyong, E-mail: zzy@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Fangohr, Hans [Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom)

2014-09-15T23:59:59.000Z

260

Magnetic field reversal of electric polarization and magnetoelectric phase diagram of the hexaferrite Ba{sub 1.3}Sr{sub 0.7}Co{sub 0.9}Zn{sub 1.1}Fe{sub 10.8}Al{sub 1.2}O{sub 22}  

SciTech Connect (OSTI)

Low magnetic field reversal of electric polarization has been demonstrated in the multiferroic Y-type hexaferrite Ba{sub 1.3}Sr{sub 0.7}Co{sub 0.9}Zn{sub 1.1}Fe{sub 10.8}Al{sub 1.2}O{sub 22} single crystal. The maximum magnetoelectric coefficient at 200?K reaches 1065?ps/m near zero magnetic field. By a systematic investigation of magnetic field dependence of magnetic and dielectric responses at various temperatures, we obtained the magnetoelectric phase diagram describing the detailed evolution of the spin-induced ferroelectric phases with temperature and magnetic field. Below 225?K, the transverse spin cone can be stabilized at zero magnetic field, which is responsible for the reversal behavior of electric polarization. Our study reveals how to eventually achieve magnetic field reversal of electric polarization in hexaferrites at room temperature.

Shen, Shipeng; Yan, Liqin; Chai, Yisheng; Cong, Junzhuang; Sun, Young, E-mail: youngsun@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2014-01-20T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Numerical studies of a one-dimensional three-spin spin-glass model with long-range interactions  

E-Print Network [OSTI]

We study a p-spin spin-glass model to understand if the finite-temperature glass transition found in the mean-field regime of p-spin models, and used to model the behavior of structural glasses, persists in the nonmean-field regime. By using a three...

Larson, Derek; Katzgraber, Helmut G.; Moore, M. A.; Young, A. P.

2010-01-01T23:59:59.000Z

262

Novel 1D coordination polymer {l_brace}Tm(Piv){sub 3{r_brace}n}: Synthesis, structure, magnetic properties and thermal behavior  

SciTech Connect (OSTI)

The new 1D coordination polymer {l_brace}Tm(Piv){sub 3{r_brace}n} (1), where Piv=OOCBu{sup t-}, was synthesized in high yield (>95%) by the reaction of thulium acetate with pivalic acid in air at 100 Degree-Sign S. According to the X-ray diffraction data, the metal atoms in compound 1 are in an octahedral ligand environment unusual for lanthanides. The magnetic and luminescence properties of polymer 1, it's the solid-phase thermal decomposition in air and under argon, and the thermal behavior in the temperature range of -50 Horizontal-Ellipsis +50 Degree-Sign S were investigated. The vaporization process of complex 1 was studied by the Knudsen effusion method combined with mass-spectrometric analysis of the gas-phase composition in the temperature range of 570-680 K. - Graphical Abstract: Novel 1D coordination polymer {l_brace}Tm(Piv){sub 3{r_brace}n} was synthesized and studied by X-ray diffraction. The magnetic, luminescence properties, the thermal behavior and the volatility for the compound {l_brace}Tm(Piv){sub 3{r_brace}n} were investigated. Black-Small-Square Highlights: Black-Right-Pointing-Pointer We synthesized the coordination polymer {l_brace}Tm(Piv){sub 3{r_brace}n}. Black-Right-Pointing-Pointer Tm atoms in polymer have the coordination number 6. Black-Right-Pointing-Pointer Polymer exhibits blue-color emission at room temperature. Black-Right-Pointing-Pointer Polymer shows high thermal stability and volatility. Black-Right-Pointing-Pointer Polymer has no phase transitions in the range of -50 Horizontal-Ellipsis +50 Degree-Sign S.

Fomina, Irina, E-mail: fomina@igic.ras.ru [N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninsky Prosp. 31, 119991 Moscow, GSP-1 (Russian Federation); Dobrokhotova, Zhanna; Aleksandrov, Grygory [N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninsky Prosp. 31, 119991 Moscow, GSP-1 (Russian Federation); Emelina, Anna; Bykov, Mikhail [Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory 1/3, 119991 Moscow, GSP-1 (Russian Federation); Malkerova, Irina [N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninsky Prosp. 31, 119991 Moscow, GSP-1 (Russian Federation); Bogomyakov, Artem [International Tomography Center, Siberian Branch of the Russian Academy of Sciences, Institutskaya Str. 3a, 630090 Novosibirsk (Russian Federation); Puntus, Lada [Kotel'nikov Institute of Radioengineering and Electronics, Russian Academy of Sciences, Mokhovaya Str. 11-7, 125009 Moscow (Russian Federation); Novotortsev, Vladimir; Eremenko, Igor [N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninsky Prosp. 31, 119991 Moscow, GSP-1 (Russian Federation)

2012-01-15T23:59:59.000Z

263

The electron-spin-nuclear-spin interaction studied by polarized neutron scattering  

Science Journals Connector (OSTI)

The directional properties of electron-proton spin interaction in an external magnetic field give rise to an anisotropic distribution of the intensity of polarized neutron scattering from dynamically polarized protons of radical molecules in solution.

Stuhrmann, H.B.

2007-11-01T23:59:59.000Z

264

Nuclear spin cooling using Overhauser field selective coherent population trapping  

E-Print Network [OSTI]

Hyperfine interactions with a nuclear spin environment fundamentally limit the coherence properties of confined electron spins in the solid-state. Here, we show that a quantum interference effect in optical absorption from two electronic spin states of a solid-state emitter can be used to prepare the surrounding environment of nuclear spins in well-defined states, thereby suppressing electronic spin dephasing. The evolution of the coupled electron-nuclei system into a coherent population trapping state by optical excitation induced nuclear spin diffusion can be described in terms of Levy flights, in close analogy with sub-recoil laser cooling of atoms. The large difference in electronic and nuclear time scales simultaneously allow for a measurement of the magnetic field produced by nuclear spins, making it possible to turn the lasers that cause the anomalous spin diffusion process off when the strength of the resonance fluorescence reveals that the nuclear spins are in the desired narrow state.

Mena Issler; Eric Kessler; Geza Giedke; Susanne Yelin; Ignacio Cirac; Mikhail Lukin; Atac Imamoglu

2010-08-20T23:59:59.000Z

265

Magnetic tunnel junctions for magnetic field sensor by using CoFeB sensing layer capped with MgO film  

SciTech Connect (OSTI)

We evaluated MgO-based magnetic tunnel junctions (MTJs) for magnetic field sensors with spin-valve-type structures in the CoFeB sensing layer capped by an MgO film in order to obtain both top and bottom interfaces of MgO/CoFeB exhibiting interfacial perpendicular magnetic anisotropy (PMA). Hysteresis of the CoFeB sensing layer in these MTJs annealed at 275?°C was suppressed at a thickness of the sensing layer below 1.2?nm by interfacial PMA. We confirmed that the CoFeB sensing layers capped with MgO suppress the thickness dependences of both the magnetoresistance ratio and the magnetic behaviors of the CoFeB sensing layer more than that of the MTJ with a Ta capping layer. MgO-based MTJs with MgO capping layers can improve the controllability of the characteristics for magnetic field sensors.

Takenaga, Takashi, E-mail: takenaga@leap.or.jp; Tsuzaki, Yosuke; Yoshida, Chikako; Yamazaki, Yuichi; Hatada, Akiyoshi; Nakabayashi, Masaaki; Iba, Yoshihisa; Takahashi, Atsushi; Noshiro, Hideyuki; Tsunoda, Koji; Aoki, Masaki; Furukawa, Taisuke; Fukumoto, Hiroshi; Sugii, Toshihiro [Low-power Electronics Association and Project (LEAP), Tsukuba 305-8569 (Japan)

2014-05-07T23:59:59.000Z

266

Magnetism of solid oxygen  

Science Journals Connector (OSTI)

Magnetic susceptibilities of single-crystal ?-O2 and preferentially oriented polycrystalline samples of ?-O2 and ?-O2 have been measured, employing a mutual-inductance bridge method. The susceptibility of paramagnetic ?-O2 is isotropic and exhibits a temperature dependence which is not strictly Curie-Weiss, due to short-range correlations and partially hindered rotation. The susceptibility of ?-O2 exhibits very little anisotropy, but has an unusual temperature dependence which is probably due to the novel behavior of the lattice constants, modulation of inplane and out-of-plane exchange interactions, and short-range order. The susceptibility of anti-ferromagnetic ?-O2 is anisotropic, and data from five differently oriented samples have been analyzed in terms of principal antiferromagnetic susceptibilities. The data are consistent with the assumption that the easy axis is the twofold axis, b??, though the direction a?? cannot be excluded. A comprehensive analysis of the present susceptibility results and other magnetic, spectroscopic, and thermal measurements is made, with special reference to ?-O2. The perpendicular susceptibility implies an unreasonably large Néel temperature, 211 K, and a correspondingly large intersublattice exchange interaction, |J2|k=19.8 K. The effects of anisotropy and zeropoint spin deviations do not reduce this estimate by more than 15%. The temperature dependence of the parallel susceptibility suggests a much smaller value for the effective exchange interaction, |J|k=5.3 K, and appears to be well accounted for assuming a single spin-wave excitation. Antiferromagnetic resonance frequencies are analyzed and shown to yield, on assuming a dominant anisotropy equal to that of the free molecule, |J2|k=4.3 K. An approximate separation of lattice and magnetic heat capacities is effected, and a value |J|k=3.0 K deduced. The data appear to require the assumption of two spin-wave modes. Except for the perpendicular susceptibility, experimental results suggest a Néel temperature between 30 and 40 K. Meanfield and other theories lead to similar estimates, assuming that |J|k is between 3 and 4 K. The effect of the anisotropy on TN is minor, and no significant spin-shortening effect is predicted. Other experimental results are considered, and a disparate set of estimates for the exchange interaction and zone-boundary spin-wave energies is discussed. Including the effects of intrasublattice exchange interactions within the context of a two-sublattice model does not seem sufficient to remove the various discrepancies. An approximate calculation of relative overlap integrals and exchange interactions between different pairs of molecules in ?-O2 is made. It is suggested that a multisublattice model for the magnetic structure, and possibly one involving noncollinear sublattices, may provide an eventual resolution of the various difficulties. A "quasi-two-dimensional" description of ?-O2 is also considered, but appears not to offer a satisfactory explanation of the unusual and imperfectly correlated properties of this phase.

Gary C. DeFotis

1981-05-01T23:59:59.000Z

267

Calculation of nuclear spin-spin coupling constants using frozen density embedding  

SciTech Connect (OSTI)

We present a method for a subsystem-based calculation of indirect nuclear spin-spin coupling tensors within the framework of current-spin-density-functional theory. Our approach is based on the frozen-density embedding scheme within density-functional theory and extends a previously reported subsystem-based approach for the calculation of nuclear magnetic resonance shielding tensors to magnetic fields which couple not only to orbital but also spin degrees of freedom. This leads to a formulation in which the electron density, the induced paramagnetic current, and the induced spin-magnetization density are calculated separately for the individual subsystems. This is particularly useful for the inclusion of environmental effects in the calculation of nuclear spin-spin coupling constants. Neglecting the induced paramagnetic current and spin-magnetization density in the environment due to the magnetic moments of the coupled nuclei leads to a very efficient method in which the computationally expensive response calculation has to be performed only for the subsystem of interest. We show that this approach leads to very good results for the calculation of solvent-induced shifts of nuclear spin-spin coupling constants in hydrogen-bonded systems. Also for systems with stronger interactions, frozen-density embedding performs remarkably well, given the approximate nature of currently available functionals for the non-additive kinetic energy. As an example we show results for methylmercury halides which exhibit an exceptionally large shift of the one-bond coupling constants between {sup 199}Hg and {sup 13}C upon coordination of dimethylsulfoxide solvent molecules.

Götz, Andreas W., E-mail: agoetz@sdsc.edu [San Diego Supercomputer Center, University of California San Diego, 9500 Gilman Dr MC 0505, La Jolla, California 92093-0505 (United States); Autschbach, Jochen [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260-3000 (United States)] [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260-3000 (United States); Visscher, Lucas, E-mail: visscher@chem.vu.nl [Amsterdam Center for Multiscale Modeling (ACMM), VU University Amsterdam, Theoretical Chemistry, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands)] [Amsterdam Center for Multiscale Modeling (ACMM), VU University Amsterdam, Theoretical Chemistry, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands)

2014-03-14T23:59:59.000Z

268

Thermodynamics of multiferroic spin chains  

Science Journals Connector (OSTI)

The minimal model to describe many spin-chain materials with ferroelectric properties is the Heisenberg model with ferromagnetic nearest-neighbor coupling J1 and antiferromagnetic next-nearest-neighbor coupling J2. Here we study the thermodynamics of this model using a density-matrix algorithm applied to transfer matrices. We find that the incommensurate spin-spin correlations—crucial for the ferroelectric properties and the analog of the classical spiral pitch angle—depend not only on the ratio J2/|J1| but also strongly on temperature. We study small easy-plane anisotropies which can stabilize a vector chiral order as well as the finite-temperature signatures of multipolar phases, stable at finite magnetic field. Furthermore, we fit the susceptibilities of LiCuVO4, LiCu2O2, and Li2ZrCuO4. Contrary to the literature, we find that for LiCuVO4 the best fit is obtained with J2?90?K and J2/|J1|?0.5 and show that these values are consistent with the observed spin incommensurability. Finally, we discuss our findings concerning the incommensurate spin-spin correlations and multipolar orders in relation to future experiments on these compounds.

J. Sirker

2010-01-26T23:59:59.000Z

269

Spin-transfer switching of orthogonal spin-valve devices at cryogenic temperatures  

SciTech Connect (OSTI)

We present the quasi-static and dynamic switching characteristics of orthogonal spin-transfer devices incorporating an out-of-plane magnetized polarizing layer and an in-plane magnetized spin valve device at cryogenic temperatures. Switching at 12?K between parallel and anti-parallel spin-valve states is investigated for slowly varied current as well as for current pulses with durations as short as 200 ps. We demonstrate 100% switching probability with current pulses 0.6?ns in duration. We also present a switching probability diagram that summarizes device switching operation under a variety of pulse durations, amplitudes, and polarities.

Ye, L., E-mail: ly17@nyu.edu; Gopman, D. B.; Rehm, L.; Backes, D.; Wolf, G.; Kent, A. D. [Department of Physics, New York University, New York, New York 10003 (United States); Ohki, T. [Raytheon BBN Technologies, Cambridge, Massachusetts 02138 (United States); Kirichenko, A. F.; Vernik, I. V.; Mukhanov, O. A. [HYPRES, 175 Clearbrook Road, Elmsford, New York 10523 (United States)

2014-05-07T23:59:59.000Z

270

E-Print Network 3.0 - amplitudes spin chains Sample Search Results  

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

of 12 spins placed in a permanent magnetic field and interact- ing through a weak Ising... nuclear-spin quantum computer in a chain of impurity paramagnetic atoms in a...

271

E-Print Network 3.0 - angle spinning 1h Sample Search Results  

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

Chemistry 9 2380 IEEE TRANSACTIONS ON MAGNETICS, VOL. 37, NO. 4, JULY 2001 General Spin Wave Instability Theory Summary: normal, as indicated. The spin wave linewidth 1H was set at...

272

Diluted ferromagnetic semiconductor Li(Zn,Mn)P with decoupled charge and spin doping  

Science Journals Connector (OSTI)

We report the discovery of a diluted magnetic semiconductor, Li(Zn,Mn)P, in which charge and spin are introduced independently via lithium off-stoichiometry and the isovalent substitution of Mn2+ for Zn2+, respectively. Isostructural to (Ga,Mn)As, Li(Zn,Mn)P was found to be a p-type ferromagnetic semiconductor with excess lithium providing charge doping. First-principles calculations indicate that excess Li is favored to partially occupy the Zn site, leading to hole doping. Ferromagnetism with Curie temperature up to 34 K is achieved while the system still shows semiconducting transport behavior.

Z. Deng; K. Zhao; B. Gu; W. Han; J. L. Zhu; X. C. Wang; X. Li; Q. Q. Liu; R. C. Yu; T. Goko; B. Frandsen; L. Liu; Jinsong Zhang; Yayu Wang; F. L. Ning; S. Maekawa; Y. J. Uemura; C. Q. Jin

2013-08-21T23:59:59.000Z

273

Structural analysis of lithium-excess lithium manganate cathode materials by 7Li magic-angle spinning nuclear magnetic resonance spectroscopy  

Science Journals Connector (OSTI)

The local structures of lithium-excess lithium manganese spinel oxides were studied by high-resolution solid-state 7Li magic-angle spinning (MAS) NMR spectroscopy. Two resonance lines at ?500 and ?555 ppm were observed for the spinels in 7Li MAS NMR spectra. Spinel stability tests in which spinel powder was stored in electrolyte solution were performed to analyze the changes in the lithium local structure after manganese dissolution. After the spinel stability test, the intensity of the resonance at ?500 ppm decreased, whereas new resonance line at 0 ppm was observed. The lithium content of the 0 ppm peak increases with the storage time in electrolyte. SEM and chemical analysis suggested a surface coating of non-spinel lithium compounds, the presence of defects on particles surface and fluorine incorporation into the aged spinel. In addition, about 60–70% of lithium remains in the spinel framework after the storage.

Hideyuki Oka; Senshi Kasahara; Tadashi Okada; Eiichi Iwata; Masaki Okada; Takayuki Shoji; Hiroshi Ohki; Tsutomu Okuda

2001-01-01T23:59:59.000Z

274

Exotic quantum magnetism and superfluidity in optical lattices  

E-Print Network [OSTI]

Chapter 4 Quantum Magnetism in spin-3/2 Systems with98 4.3.1 Quantum magnetism in 1D chains . . . . . . . . .98 4.3.2 Quantum magnetism in 2D square lattices . . . . 108

Hung, Hsiang-Hsuan

2011-01-01T23:59:59.000Z

275

Magnetic Resonance Imaging in Soil Science  

Science Journals Connector (OSTI)

Magnetic resonance imaging is based upon the physical effect of nuclear magnetic resonance (NMR) of spin bearing atomic...1991; Blümich, 2000...). The most important NMR active nuclei in soil science applications...

Andreas Pohlmeier

2014-08-01T23:59:59.000Z

276

Modulated magnetic structure in quasi-one-dimensional clinopyroxene NaFeGe{sub 2}O{sub 6}  

SciTech Connect (OSTI)

The magnetic structure of the NaFeGe{sub 2}O{sub 6} monoclinic compound has been experimentally investigated using the elastic scattering of neutrons. At a temperature of 1.6 K, an incommensurate magnetic structure has been observed in the form of an antiferromagnetic helix formed by a pairs of the spins of the Fe{sup 3+} ions with helical modulation in the ac plane of the crystal lattice. The wave vector of the magnetic structure has been determined and its temperature behavior has been studied. The analysis of the temperature dependences of the specific heat and susceptibility, as well as the isotherms of the field dependence of the magnetization, has revealed the existence of not only the order-disorder magnetic phase transition at the point T{sub N} = 13 K, but also an additional magnetic phase transition at the point T{sub c} = 11.5 K, which is assumingly an orientation phase transition.

Drokina, T. V., E-mail: tvd@iph.krasn.ru; Petrakovskii, G. A. [Russian Academy of Sciences, Kirensky Institute of Physics, Siberian Branch (Russian Federation); Keller, L.; Schefer, J. [ETH Zuerich and Paul Scherrer Institut, Laboratory for Neutron Scattering (Switzerland); Balaev, A. D.; Kartashev, A. V.; Ivanov, D. A. [Russian Academy of Sciences, Kirensky Institute of Physics, Siberian Branch (Russian Federation)

2011-01-15T23:59:59.000Z

277

Low field magnetic resonance imaging  

DOE Patents [OSTI]

A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.

Pines, Alexander (Berkeley, CA); Sakellariou, Dimitrios (Billancourt, FR); Meriles, Carlos A. (Fort Lee, NJ); Trabesinger, Andreas H. (London, GB)

2010-07-13T23:59:59.000Z

278

Magnetism of Co nanocluster films  

Science Journals Connector (OSTI)

A cluster-beam technique is used to produce nearly monodispersed nanoclusters of Co while independently varying their size and concentration. The Co clusters are embedded in Cu and SiO2 to form films with cluster size varying from 300 to 9000 atoms and Co concentration varying from 10 to 50 vol %. The Co magnetization (Ms) increases with increasing cluster size and decreases with increasing Co concentration for a given cluster size but is always less than the bulk value. First-principles calculations are used to analyze the experimental data in terms of the local environment effects at the cluster-matrix interface and spin-glass-like behavior due to the strong ferro- and antiferromagnetic intercluster exchange interactions for small separations.

Y. Qiang; R. F. Sabiryanov; S. S. Jaswal; Y. Liu; H. Haberland; D. J. Sellmyer

2002-08-02T23:59:59.000Z

279

Intrinsic Spin-Orbit Interaction in Graphene  

E-Print Network [OSTI]

In graphene, we report the first theoretical demonstration of how the intrinsic spin orbit interaction can be deduced from the theory and how it can be controlled by tuning a uniform magnetic field, and/or by changing the strength of a long range Coulomb like impurity (adatom), as well as gap parameter. In the impurity context, we find that intrinsic spin-orbit interaction energy may be enhanced by increasing the strength of magnetic field and/or by decreasing the band gap mass term. Additionally, it may be strongly enhanced by increasing the impurity strength. Furthermore, from the proposal of Kane and Mele [Phys. Rev. Lett. 95, 226801 (2005)], it was discussed that the pristine graphene has a quantized spin Hall effect regime where the Rashba type spin orbit interaction term is smaller than that of intrinsic one. Our analysis suggest the nonexistence of such a regime in the ground state of flat graphene.

B. S. Kandemir

2012-05-03T23:59:59.000Z

280

Demand Response Spinning Reserve Demonstration  

E-Print Network [OSTI]

F) Enhanced ACP Date RAA ACP Demand Response – SpinningReserve Demonstration Demand Response – Spinning Reservesupply spinning reserve. Demand Response – Spinning Reserve

2007-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Spin Waves and Neutron Scattering  

Science Journals Connector (OSTI)

A review is given of the problems in this field and of the possibilities opened up by the fact that neutron scattering gives access to the time?dependent spin?correlation function in magnets over virtually the whole range of q t and T. New experimental results are given in connection with magnon energy linewidth and renormalization and some data are presented for the spin?wave stiffness of bcc 3d transition?metal alloys as a function of electron concentration showing effects explained by the electronic density?of?states curve. It is pointed out that the ground?state fluctuations of magnets give rise to effects in the formulas for neutron scattering.

R. D. Lowde

1965-01-01T23:59:59.000Z

282

Cyanide clusters of ReII with 3d metal ions and their magnetic properties: incorporating anisotropic ions into metal-cyanide clusters with high spin magnetic ground states  

E-Print Network [OSTI]

?????????????????... 69 III METAL-CYANIDE CUBES OF ReII AND MID TRANSITION SERIES 3d IONS {[MCl]4[Re(triphos)(CN)3]4} M = Mn, Fe, Co; AND THEIR MAGNETIC PROPERTIES??????????...72 I. Introduction?????????????????????. 72 II.... Experimental Section????...................................................... 74 A. Starting Materials??........................................................ 74 B. Synthesis of Molecular Cubes of Re4Mn4, Re4Fe4, Re 4Co4...

Schelter, Eric John

2005-08-29T23:59:59.000Z

283

Absence of exponential sensitivity to small perturbations in nonintegrable systems of spins 1/2  

Science Journals Connector (OSTI)

We show that macroscopic nonintegrable lattices of spins 1/2, which are often considered to be chaotic, do not exhibit the basic property of classical chaotic systems, namely, exponential sensitivity to small perturbations. We compare chaotic lattices of classical spins and nonintegrable lattices of spins 1/2 in terms of their magnetization responses to an imperfect reversal of spin dynamics known as Loschmidt echo. In the classical case, magnetization is exponentially sensitive to small perturbations with a characteristic exponent equal to twice the value of the largest Lyapunov exponent of the system. In the case of spins 1/2, magnetization is only power-law sensitive to small perturbations.

B. V. Fine; T. A. Elsayed; C. M. Kropf; A. S. de Wijn

2014-01-31T23:59:59.000Z

284

E-Print Network 3.0 - artificial molecular magnets Sample Search...  

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

ligands. The calculations show that the inherent spin magnetic... for new nanoscale magnetic materials. Single molecular ... Source: Kern, Klaus - Nanoscale Science...

285

Current-based detection of nonlocal spin transport in graphene for spin-based logic applications  

SciTech Connect (OSTI)

Graphene has been proposed for novel spintronic devices due to its robust and efficient spin transport properties at room temperature. Some of the most promising proposals require current-based readout for integration purposes, but the current-based detection of spin accumulation has not yet been developed. In this work, we demonstrate current-based detection of spin transport in graphene using a modified nonlocal geometry. By adding a variable shunt resistor in parallel to the nonlocal voltmeter, we are able to systematically cross over from the conventional voltage-based detection to current-based detection. As the shunt resistor is reduced, the output current from the spin accumulation increases as the shunt resistance drops below a characteristic value R*. We analyze this behavior using a one-dimensional drift-diffusion model, which accounts well for the observed behavior. These results provide the experimental and theoretical foundation for current-based detection of nonlocal spin transport.

Wen, Hua; Amamou, Walid [Department of Physics and Astronomy, University of California, Riverside, California 92521 (United States); Zhu, Tiancong; Luo, Yunqiu; Kawakami, Roland K., E-mail: roland.kawakami@ucr.edu [Department of Physics and Astronomy, University of California, Riverside, California 92521 (United States); Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)

2014-05-07T23:59:59.000Z

286

Manipulation of the spin-orbit coupling using the Dirac equation for spin-dependent potentials  

Science Journals Connector (OSTI)

A scheme is presented that allows one to decompose the spin-orbit coupling operator into two parts within calculations based on the Dirac equation for spin-dependent potentials. The first term lifts energetic degeneracies but leaves the spin as a good quantum number, while the second term causes hybridization of states with a different spin character. To investigate the importance of these terms and of the mechanism connected to them a number of model calculations for the dispersion relation, the spin-orbit-induced orbital magnetic moment, and the magneto-optical Kerr effect in several transition metal systems have been performed by retaining just one of them. In all cases studied it was found that the first term is by far the most important source for spin-orbit-induced phenomena.

H. Ebert, H. Freyer, and M. Deng

1997-10-15T23:59:59.000Z

287

Efficient readout of a single spin state in diamond via spin-to-charge conversion  

E-Print Network [OSTI]

Efficient readout of individual electronic spins associated with atom-like impurities in the solid state is essential for applications in quantum information processing and quantum metrology. We demonstrate a new method for efficient spin readout of nitrogen-vacancy (NV) centers in diamond. The method is based on conversion of the electronic spin state of the NV to a charge state distribution, followed by single-shot readout of the charge state. Conversion is achieved through a spin-dependent photoionization process in diamond at room temperature. Using NVs in nanofabricated diamond beams, we demonstrate that the resulting spin readout noise is within a factor of three of the spin projection noise level. Applications of this technique for nanoscale magnetic sensing are discussed.

B. J. Shields; Q. P. Unterreithmeier; N. P. de Leon; H. Park; M. D. Lukin

2014-10-01T23:59:59.000Z

288

Competition between magnetism and superconductivity in TmNi{sub 2}B{sub 2}C observed by muon-spin rotation  

SciTech Connect (OSTI)

We report muon-spin-rotation measurements of the internal field in the rare-earth nickel boride carbide superconductor TmNi{sub 2}B{sub 2}C from 100 mK up to well above the superconducting transition temperature ({ital T}{sub {ital c}}=9.5 K). An oscillatory muon response indicates that the muon is affected by a quasistatic local field that follows a {ital T}{sup {minus}1} dependence over a wide temperature range and without interruption at the superconducting transition. The corresponding relaxation rate remains constant in the normal state, but begins to rise very sharply with decreasing temperature below {ital T}{sub {ital c}} scaling approximately with the local field down to its maximum at 2.5 K. The quasistatic internal field may be attributed to a spiral structure or slow three-dimensional correlations of the Tm moments. Decoupling experiments reveal a dynamic depolarization mechanism which may tentatively be ascribed to fast two-dimensional correlations of the Ni moments, slowed by the onset of superconductivity.

Cooke, D.W.; Smith, J.L. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Blundell, S.J.; Chow, K.H.; Pattenden, P.A.; Pratt, F.L. [Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom)] [Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom); Cox, S.F.J.; Brown, S.R. [ISIS, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX (United Kingdom)] [ISIS, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX (United Kingdom); Morrobel-Sosa, A. [California Polytechnic State University, San Luis Obispo, California 93407 (United States)] [California Polytechnic State University, San Luis Obispo, California 93407 (United States); Lichti, R.L. [Department of Physics, Texas Tech University, Lubbock, Texas 79409 (United States)] [Department of Physics, Texas Tech University, Lubbock, Texas 79409 (United States); Gupta, L.C.; Nagarajan, R.; Hossain, Z. [Tata Institute of Fundamental Research, Homi Bhabha Road, Bombay 400 005 (India)] [Tata Institute of Fundamental Research, Homi Bhabha Road, Bombay 400 005 (India); Mazumdar, C. [Indian Institute of Technology, Powai, Bombay 400 076 (India)] [Indian Institute of Technology, Powai, Bombay 400 076 (India); Godart, C. [UPR-209, Centre National de la Recherche Scientifique, 92195 Meudon Cedex (France)] [UPR-209, Centre National de la Recherche Scientifique, 92195 Meudon Cedex (France)

1995-08-01T23:59:59.000Z

289

E-Print Network 3.0 - accurately measuring behavioral Sample...  

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

expected to dominate device behavior at this range, the metrology... element, film edge metrology, addresses the role of the edge on magnetic behavior uniformity in magnetic......

290

Observation of propagating edge spin waves modes  

SciTech Connect (OSTI)

Broadband magnetization response of equilateral triangular 1000 nm Permalloy dots has been studied under an in-plane magnetic field, applied parallel (buckle state), and perpendicular (Y state) to the triangles base. Micromagnetic simulations identify edge spin waves (E-SWs) in the buckle state as SWs propagating along the two adjacent edges. These quasi one-dimensional spin waves emitted by the vertex magnetic charges gradually transform from propagating to standing due to interference and are weakly affected by dipolar interdot interaction and variation of the aspect ratio. Spin waves in the Y state have a two dimensional character. These findings open perspectives for implementation of the E-SWs in magnonic crystals and thin films.

Lara, A.; Aliev, F. G., E-mail: farkhad.aliev@uam.es [Dpto. Física de la Materia Condensada C-III, Instituto Nicolas Cabrera (INC) and Condensed Matter Physics Institute (IFIMAC), Universidad Autónoma de Madrid, Madrid 28049 (Spain); Metlushko, V. [Department of Electrical and Computer Engineering, University of Illinois, Chicago, Illinois 60607 (United States)

2013-12-07T23:59:59.000Z

291

Environment Assisted Metrology with Spin Qubit  

E-Print Network [OSTI]

We investigate the sensitivity of a recently proposed method for precision measurement [Phys. Rev. Lett. 106, 140502 (2011)], focusing on an implementation based on solid-state spin systems. The scheme amplifies a quantum sensor response to weak external fields by exploiting its coupling to spin impurities in the environment. We analyze the limits to the sensitivity due to decoherence and propose dynamical decoupling schemes to increase the spin coherence time. The sensitivity is also limited by the environment spin polarization; therefore we discuss strategies to polarize the environment spins and present a method to extend the scheme to the case of zero polarization. The coherence time and polarization determine a figure of merit for the environment's ability to enhance the sensitivity compared to echo-based sensing schemes. This figure of merit can be used to engineer optimized samples for high-sensitivity nanoscale magnetic sensing, such as diamond nanocrystals with controlled impurity density.

Cappellaro, P; Hodges, J S; Jiang, L; Maze, J R; Sørensen, A S; Lukin, M D

2012-01-01T23:59:59.000Z

292

Current heating induced spin Seebeck effect  

SciTech Connect (OSTI)

A measurement technique for the spin Seebeck effect is presented, wherein the normal metal layer used for its detection is exploited simultaneously as a resistive heater and thermometer. We show how the various contributions to the measured total signal can be disentangled, allowing to extract the voltage signal solely caused by the spin Seebeck effect. To this end, we performed measurements as a function of the external magnetic field strength and its orientation. We find that the effect scales linearly with the induced rise in temperature, as expected for the spin Seebeck effect.

Schreier, Michael, E-mail: michael.schreier@wmi.badw.de; Roschewsky, Niklas; Dobler, Erich; Meyer, Sibylle; Huebl, Hans; Goennenwein, Sebastian T. B. [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany)] [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Gross, Rudolf [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany) [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, Technische Universität München, Garching (Germany)

2013-12-09T23:59:59.000Z

293

Quantum Decoherence of the Central Spin in a Sparse System of Dipolar Coupled Spins  

E-Print Network [OSTI]

The central spin decoherence problem has been researched for over 50 years in the context of both nuclear magnetic resonance and electron spin resonance. Until recently, theoretical models have employed phenomenological stochastic descriptions of the bath-induced noise. During the last few years, cluster expansion methods have provided a microscopic, quantum theory to study the spectral diffusion of a central spin. These methods have proven to be very accurate and efficient for problems of nuclear-induced electron spin decoherence in which hyperfine interactions with the central electron spin are much stronger than dipolar interactions among the nuclei. We provide an in-depth study of central spin decoherence for a canonical scale-invariant all-dipolar spin system. We show how cluster methods may be adapted to treat this problem in which central and bath spin interactions are of comparable strength. Our extensive numerical work shows that a properly modified cluster theory is convergent for this problem even as simple perturbative arguments begin to break down. By treating clusters in the presence of energy detunings due to the long-range (diagonal) dipolar interactions of the surrounding environment and carefully averaging the effects over different spin states, we find that the nontrivial flip-flop dynamics among the spins becomes effectively localized by disorder in the energy splittings of the spins. This localization effect allows for a robust calculation of the spin echo signal in a dipolarly coupled bath of spins of the same kind, while considering clusters of no more than 6 spins. We connect these microscopic calculation results to the existing stochastic models. We, furthermore, present calculations for a series of related problems of interest for candidate solid state quantum bits including donors and quantum dots in silicon as well as nitrogen-vacancy centers in diamond.

Wayne M. Witzel; Malcolm S. Carroll; Lukasz Cywinski; S. Das Sarma

2012-08-02T23:59:59.000Z

294

A Large Sample Volume Magic Angle Spinning Nuclear Magnetic Resonance Probe for In-Situ Investigations with Constant Flow of Reactants  

SciTech Connect (OSTI)

A large-sample-volume constant-flow magic angle sample spinning (CF-MAS) NMR probe is reported for in-situ studies of the reaction dynamics, stable intermediates/transition states, and mechanisms of catalytic reactions. In our approach, the reactants are introduced into the catalyst bed using a fixed tube at one end of the MAS rotor while a second fixed tube, linked to a vacuum pump, is attached at the other end of the rotor. The pressure difference between both ends of the catalyst bed inside the sample cell space forces the reactants flowing through the catalyst bed, which improves the diffusion of the reactants and products. This design allows the use of a large sample volume for enhanced sensitivity and thus permitting in-situ 13C CF-MAS studies at natural abundance. As an example of application, we show that reactants, products and reaction transition states associated with the 2-butanol dehydration reaction over a mesoporous silicalite supported heteropoly acid catalyst (HPA/meso-silicalite-1) can all be detected in a single 13C CF-MAS NMR spectrum at natural abundance. Coke products can also be detected at natural 13C abundance and under the stopped flow condition. Furthermore, 1H CF-MAS NMR is used to identify the surface functional groups of HPA/meso-silicalite-1 under the condition of in-situ drying . We also show that the reaction dynamics of 2-butanol dehydration using HPA/meso-silicalite-1 as a catalyst can be explored using 1H CF-MAS NMR.

Hu, Jian Z.; Sears, Jesse A.; Mehta, Hardeep S.; Ford, Joseph J.; Kwak, Ja Hun; Zhu, Kake; Wang, Yong; Liu, Jun; Hoyt, David W.; Peden, Charles HF

2012-02-21T23:59:59.000Z

295

Spin transfer and coherence in coupled quantum wells  

Science Journals Connector (OSTI)

Spin dynamics of optically excited electrons confined in asymmetric coupled quantum wells are investigated through time-resolved Faraday rotation experiments. The interwell coupling is shown to depend on applied electric field and barrier thickness. We observe three coupling regimes: independent spin precession in isolated quantum wells, incoherent spin transfer between single-well states, and coherent spin transfer in a highly coupled system. Relative values of the interwell tunneling time, the electron-spin lifetime, and the Larmor precession period appear to govern this behavior.

M. Poggio, G. M. Steeves, R. C. Myers, N. P. Stern, A. C. Gossard, and D. D. Awschalom

2004-09-16T23:59:59.000Z

296

Density of defects and the scaling law of the entanglement entropy in quantum phase transition of one-dimensional spin systems induced by a quench  

SciTech Connect (OSTI)

We have studied quantum phase transition induced by a quench in different one-dimensional spin systems. Our analysis is based on the dynamical mechanism which envisages nonadiabaticity in the vicinity of the critical point. This causes spin fluctuation which leads to the random fluctuation of the Berry phase factor acquired by a spin state when the ground state of the system evolves in a closed path. The two-point correlation of this phase factor is associated with the probability of the formation of defects. In this framework, we have estimated the density of defects produced in several one-dimensional spin chains. At the critical region, the entanglement entropy of a block of L spins with the rest of the system is also estimated which is found to increase logarithmically with L. The dependence on the quench time puts a constraint on the block size L. It is also pointed out that the Lipkin-Meshkov-Glick model in point-splitting regularized form appears as a combination of the XXX model and Ising model with magnetic field in the negative z axis. This unveils the underlying conformal symmetry at criticality which is lost in the sharp point limit. Our analysis shows that the density of defects as well as the scaling behavior of the entanglement entropy follows a universal behavior in all these systems.

Basu, Banasri; Bandyopadhyay, Pratul; Majumdar, Priyadarshi [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata 700 108 (India); Jyotinagar Bidyasree Niketan H.S. School, 41 Jyotinagar, Kolkata 700 108 (India)

2011-03-15T23:59:59.000Z

297

Synthesis and anomalous magnetic properties of hexagonal CoO nanoparticles  

SciTech Connect (OSTI)

Highlights: {yields} The as-synthesized CoO nanoparticles are of pyramid configuration with hcp structure. {yields} The hexagonal CoO particles do not exhibit antiferromagnetic transition around 300 K. {yields} The CoO particles have relative large saturation magnetization and coercivity at 5 K. {yields} The shift of hysteresis loops is consistent with the result of multisublattice model. {yields} The particles contain intrinsic antiferromagnetic structure and uncompensated spins. -- Abstract: CoO nanoparticles in the 38-93 nm range have been prepared by thermal decomposition. The particles were characterized to be pyramid shape with a hexagonal close-packed structure. Their anomalous magnetic behavior includes: (i) vanishing of antiferromagnetic transition around 300 K; (ii) creation of hysteresis below a blocking temperature of 6-11 K; (iii) presence of relatively large moments and coercivities accompany with specific loop shifts at 5 K; and (iv) appearance of an additional small peak located in low field in the electron spin resonance spectrum. Further, the present results provide evidence for the existence of uncompensated surface spins. The coercivity and exchange bias decrease with increasing particle size, indicating a distinct size effect. These observations can be explained by the multisublattice model, in which the reduced coordination of surface spins causes a fundamental change in the magnetic order throughout the total CoO particle.

He, Xuemin [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)] [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Shi, Huigang, E-mail: shihuig@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)] [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

2011-10-15T23:59:59.000Z

298

A polarized neutron reflectometry study of the spin glass freezing in a 29 nm thick AuFe film  

Science Journals Connector (OSTI)

We performed polarized neutron reflectometry (PNR) experiments on a 29 nm thick Au93Fe7 film in a temperature range from 295 K down to 2 K in a vertical magnetic field up to 6 T. These high-field experiments were performed on the C5 spectrometer in Chalk River, Canada, using a split-pair cryomagnet. The magnetization as determined by PNR can be described with a Brillouin function from 295 K down to 50 K assuming the magnetic moment of isolated Fe atoms, i.e. 4 ? B per Fe atom. Below 50 K the onset of the spin-glass freezing is observed as a strong deviation from this Brillouin type behavior of isolated atoms.

H. Fritzsche; M. Saoudi; K. Temst; C. Van Haesendonck

2007-01-01T23:59:59.000Z

299

The Unique High-Pressure Behavior of Curium Probed Further Using Alloys  

SciTech Connect (OSTI)

The changing role of the 5f electrons across the actinide series has been of prime interest for many years. The remarkable behavior of americium's 5f electrons under pressure was determined experimentally a few years ago and it precipitated a strong interest in the heavy element community. Theoretical treatments of americium's behavior under pressure followed and continue today. Experimental and theoretical findings regarding curium's behavior under pressure have shown that the pressure behavior of curium was not a mirror image of that for americium. Rather, one of the five crystallographic phases observed with curium (versus four for americium) was a unique monoclinic structure whose existence is due to a spin stabilization effect by curium's 5f{sup 7} electronic configuration and its half-filled 5f-shell. We review briefly the behavior of pure curium under pressure but focus on the pressure behaviors of three curium alloys with the intent of comparing them with pure curium. An important experimental finding confirmed by theoretical computations, is that dilution of curium with its near neighbors is sufficient to prevent the formation of the unique C2/c phase that appears in pure Cm metal under pressure. As this unique C2/c phase is very sensitive to having a 5f{sup 7} configuration to maximize the magnetic spin polarization, dilution of this state with adjacent actinide neighbors reduces its stability.

Heathman, S. [European Commission Joint Research Centre; Haire, Richard {Dick} G [ORNL; LeBihan, T. [CEA-Centre de Valduc, Is-sur-Tille, France; Ahuja, R. [Uppsala University, Uppsala, Sweden; Li, S. [Virginia Commonwealth University, Richland; Luo, W. [Uppsala University, Uppsala, Sweden; Johansson, B. [Royal Institute of Technology, Stockholm, Sweden

2007-01-01T23:59:59.000Z

300

Magnetic Interactions in the Geometrically Frustrated Triangular Lattice Antiferromagnet CuFeO2  

SciTech Connect (OSTI)

The spin-wave excitations of the geometrically frustrated triangular lattice antiferromagnet CuFeO2 have been measured using high resolution inelastic neutron scattering. Antiferromagnetic interactions up to third nearest neighbors in the ab plane (J1, J2, J3, with J2=J1 0:44 and J3=J1 0:57), as well as out-of-plane coupling (Jz, with Jz=J1 0:29) are required to describe the spin-wave dispersion relations, indicating a three-dimensional character of the magnetic interactions. Two energy dips in the spin-wave dispersion occur at the incommensurate wave vectors associated with multiferroic phase and can be interpreted as dynamic precursors to the magnetoelectric behavior in this system.

Ye, Feng [ORNL; Fernandez-Baca, Jaime A [ORNL; Fishman, Randy Scott [ORNL; Ren, Y. [Argonne National Laboratory (ANL); Qiu, Y. [National Institute of Standards and Technology (NIST); Kimura, T. [Osaka University

2007-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Magnetic Interaction in the Geometrically Frustrated Triangular LatticeAntiferromagnet CuFeO2  

SciTech Connect (OSTI)

The spin wave excitations of the geometrically frustrated triangular lattice antiferromagnet (TLA) CuFeO2 have been measured using high resolution inelastic neutron scattering. Antiferromagnetic interactions up to third nearest neighbors in the ab plane (J1, J2, J3, with J2=J1 0:44 and J3=J1 0:57), as well as out-of-plane coupling (Jz, with Jz=J1 0:29) are required to describe the spin wave dispersion relations, indicating a three dimensional character of the magnetic interactions. Two energy deeps in the spin wave dispersion occur at the incommensurate wavevectors associated with multiferroic phase, and can be interpreted as dynamic precursors to the magnetoelectric behavior in this system.

Ye, Feng [ORNL; Fernandez-Baca, Jaime A [ORNL; Fishman, Randy Scott [ORNL; Ren, Y. [Argonne National Laboratory (ANL); Kang, H. J. [National Institute of Standards and Technology (NIST); Qiu, Y. [National Institute of Standards and Technology (NIST); Kimura, T. [Los Alamos National Laboratory (LANL)

2007-01-01T23:59:59.000Z

302

Magnetic susceptibility of PrMg3 at ultra low temperatures  

Science Journals Connector (OSTI)

We report susceptibility measurements of PrMg3 with a non-magnetic T3 crystalline-electric-field ground state down to 0.3 mK. The susceptibility shows the Van-Vleck-like behavior with an additional logarithmic temperature dependence below 10 K. Furthermore, the susceptibility exhibits a small peak around 0.1 K, which is attributed to the quenching of the multipole degrees of freedom. Below 30 mK, the susceptibility is almost constant down to the lowest temperature without showing the contribution of Pr nuclear spins. The disappearance of nuclear spin contribution suggests that the quenching of the multipole degrees of freedom strongly affects the nuclear spin system.

J Yoshida; S Abe; A Tada; H Tsujii; K Matsumoto; H Suzuki; H S Suzuki

2009-01-01T23:59:59.000Z

303

Complex behavior in simple spin systems  

E-Print Network [OSTI]

5. J. Cavanagh, W. J. Fairbrother, A. B. P. III and N. J.7. J. Cavanagh, W. J. Fairbrother, A. B. P. III and N. J.

Bush, S.D.

2010-01-01T23:59:59.000Z

304

Spin-valve photodiode Ian Appelbaum,a)  

E-Print Network [OSTI]

Spin-valve photodiode Ian Appelbaum,a) D. J. Monsma, K. J. Russell, V. Narayanamurti, and C. M using internal photoemission to generate hot electrons in magnetic multilayer Schottky photodiodes

Russell, Kasey

305

Electric-dipole-induced spin resonance in disordered semiconductors  

E-Print Network [OSTI]

ARTICLES Electric-dipole-induced spin resonance in disordered semiconductors MATHIAS DUCKHEIM One of the hallmarks of spintronics is the control of magnetic moments by electric fields enabled in such structures is electric-dipole-induced spin resonance (EDSR), where the radio-frequency fields driving

Loss, Daniel

306

Experimental Heat-Bath Cooling of Spins  

E-Print Network [OSTI]

Algorithmic cooling (AC) is a method to purify quantum systems, such as ensembles of nuclear spins, or cold atoms in an optical lattice. When applied to spins, AC produces ensembles of highly polarized spins, which enhance the signal strength in nuclear magnetic resonance (NMR). According to this cooling approach, spin-half nuclei in a constant magnetic field are considered as bits, or more precisely, quantum bits, in a known probability distribution. Algorithmic steps on these bits are then translated into specially designed NMR pulse sequences using common NMR quantum computation tools. The $algorithmic$ cooling of spins is achieved by alternately combining reversible, entropy-preserving manipulations (borrowed from data compression algorithms) with $selective$ $reset$, the transfer of entropy from selected spins to the environment. In theory, applying algorithmic cooling to sufficiently large spin systems may produce polarizations far beyond the limits due to conservation of Shannon entropy. Here, only selective reset steps are performed, hence we prefer to call this process "heat-bath" cooling, rather than algorithmic cooling. We experimentally implement here two consecutive steps of selective reset that transfer entropy from two selected spins to the environment. We performed such cooling experiments with commercially-available labeled molecules, on standard liquid-state NMR spectrometers. Our experiments yielded polarizations that $bypass$ $Shannon's$ $entropy$-$conservation$ $bound$, so that the entire spin-system was cooled. This paper was initially submitted in 2005, first to Science and then to PNAS, and includes additional results from subsequent years (e.g. for resubmission in 2007). The Postscriptum includes more details.

Gilles Brassard; Yuval Elias; José M. Fernandez; Haggai Gilboa; Jonathan A. Jones; Tal Mor; Yossi Weinstein; Li Xiao

2014-04-28T23:59:59.000Z

307

Line Broadening and Decoherence of Electron Spins in Phosphorus-Doped Silicon Due to Environmental 29^Si Nuclear Spins  

E-Print Network [OSTI]

Phosphorus-doped silicon single crystals with 0.19 % effect of environmental 29^Si nuclear spins on the donor electron spin is systematically studied. The linewidth as a function of f shows a good agreement with theoretical analysis. We also report the phase memory time T_M of the donor electron spin dependent on both f and the crystal axis relative to the external magnetic field.

Eisuke Abe; Akira Fujimoto; Junichi Isoya; Satoshi Yamasaki; Kohei M. Itoh

2005-12-16T23:59:59.000Z

308

Electronic Structure and Magnetism in Diluted Magnetic Semiconductors  

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

Electronic Structure and Electronic Structure and Magnetism in Diluted Magnetic Semiconductors Electronic Structure and Magnetism in Diluted Magnetic Semiconductors Print Wednesday, 29 November 2006 00:00 The possibility of using electrons' spins in addition to their charge in information technology has created much enthusiasm for a new field of electronics popularly known as "spintronics." An intensely studied approach to obtaining spin-polarized carriers for data-storage devices is the use of diluted magnetic semiconductors created by doping ions like Mn, Fe, or Co having a net spin into a semiconducting host such as GaAs, ZnO, or GaN. The interaction among these spins leads to ferromagnetic order at low temperatures, which is necessary to create spin-polarized carriers. A research team working at ALS Beamline 4.0.2 and European Synchrotron Radiation Facility Beamline ID8 made a big leap forward in clarifying the microscopic picture of magnetism and anisotropy in Mn-doped GaAs by resolving localized and hybridized d states using angle-dependent x-ray magnetic circular dichroism (XMCD) measurements.

309

Electronic Structure and Magnetism in Diluted Magnetic Semiconductors  

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

Electronic Structure and Magnetism in Diluted Magnetic Semiconductors Print Electronic Structure and Magnetism in Diluted Magnetic Semiconductors Print The possibility of using electrons' spins in addition to their charge in information technology has created much enthusiasm for a new field of electronics popularly known as "spintronics." An intensely studied approach to obtaining spin-polarized carriers for data-storage devices is the use of diluted magnetic semiconductors created by doping ions like Mn, Fe, or Co having a net spin into a semiconducting host such as GaAs, ZnO, or GaN. The interaction among these spins leads to ferromagnetic order at low temperatures, which is necessary to create spin-polarized carriers. A research team working at ALS Beamline 4.0.2 and European Synchrotron Radiation Facility Beamline ID8 made a big leap forward in clarifying the microscopic picture of magnetism and anisotropy in Mn-doped GaAs by resolving localized and hybridized d states using angle-dependent x-ray magnetic circular dichroism (XMCD) measurements.

310

Electronic Structure and Magnetism in Diluted Magnetic Semiconductors  

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

Electronic Structure and Magnetism in Diluted Magnetic Semiconductors Print Electronic Structure and Magnetism in Diluted Magnetic Semiconductors Print The possibility of using electrons' spins in addition to their charge in information technology has created much enthusiasm for a new field of electronics popularly known as "spintronics." An intensely studied approach to obtaining spin-polarized carriers for data-storage devices is the use of diluted magnetic semiconductors created by doping ions like Mn, Fe, or Co having a net spin into a semiconducting host such as GaAs, ZnO, or GaN. The interaction among these spins leads to ferromagnetic order at low temperatures, which is necessary to create spin-polarized carriers. A research team working at ALS Beamline 4.0.2 and European Synchrotron Radiation Facility Beamline ID8 made a big leap forward in clarifying the microscopic picture of magnetism and anisotropy in Mn-doped GaAs by resolving localized and hybridized d states using angle-dependent x-ray magnetic circular dichroism (XMCD) measurements.

311

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

SciTech Connect (OSTI)

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, ?{sub ac}(T), shows no signature of spin-glass behavior. ?”(T) exhibits a sudden increase at low temperatures which is due to ordering of Yb{sup 3+} sublattice.

Sattibabu, Bhumireddi, E-mail: bsb.satti@gmail.com; Bhatnagar, Anil K., E-mail: bsb.satti@gmail.com; Mohan, Dasari, E-mail: bsb.satti@gmail.com; Das, Dibakar, E-mail: bsb.satti@gmail.com; Sundararaman, Mahadevan, E-mail: bsb.satti@gmail.com [School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad-500046 (India); Siruguri, Vasudeva; Rayaprol, Sudhindra [UGC-DAE Consortium for Scientific Research, Mumbai Centre, R-5 Shed, Bhabha Atomic Research Centre, Mumbai-400085 (India)

2014-04-24T23:59:59.000Z

312

Spin-polarization and spin-dependent logic gates in a double quantum ring based on Rashba spin-orbit effect: Non-equilibrium Green's function approach  

SciTech Connect (OSTI)

Spin-dependent electron transport in an open double quantum ring, when each ring is made up of four quantum dots and threaded by a magnetic flux, is studied. Two independent and tunable gate voltages are applied to induce Rashba spin-orbit effect in the quantum rings. Using non-equilibrium Green's function formalism, we study the effects of electron-electron interaction on spin-dependent electron transport and show that although the electron-electron interaction induces an energy gap, it has no considerable effect when the bias voltage is sufficiently high. We also show that the double quantum ring can operate as a spin-filter for both spin up and spin down electrons. The spin-polarization of transmitted electrons can be tuned from ?1 (pure spin-down current) to +1 (pure spin-up current) by changing the magnetic flux and/or the gates voltage. Also, the double quantum ring can act as AND and NOR gates when the system parameters such as Rashba coefficient are properly adjusted.

Eslami, Leila, E-mail: Leslami@iust.ac.ir; Esmaeilzadeh, Mahdi, E-mail: mahdi@iust.ac.ir [Department of Physics, Iran University of Science and Technology, Tehran 16846 (Iran, Islamic Republic of)

2014-02-28T23:59:59.000Z

313

Magellan Tackles the Mysterious Proton Spin  

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

Magellan Tackles Magellan Tackles Mysterious Proton Spin Magellan Tackles Mysterious Proton Spin July 28, 2011 | Tags: Accelerator Science, Data Transfer, ESnet, Magellan Linda Vu, lvu@lbl.gov, +1 510 495 2402 The STAR experiment's detector records the decay of subatomic smash-ups to uncover how the fundamental building blocks of the universe work. What makes a proton spin? That is one of the biggest mysteries in physics. Although researchers do not fully understand the underlying physics of this phenomenon, they do know that it contributes to the stability of the universe, magnetic interactions, and are a vital component of technologies like Magnetic Resonance Imaging (MRI) machines that are used in hospitals around the globe. To solve this mystery, researchers are smashing together polarized proton

314

Unit-Spin Propagation Functions and Form Factors  

Science Journals Connector (OSTI)

Source theory is used to derive a representation for the propagation function of a unit-spin meson. The asymptotic behavior for large momenta resembles that observed in electromagnetic form factors.

Julian Schwinger

1971-04-15T23:59:59.000Z

315

National High Magnetic Field Laboratory: Museum of Electricity...  

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

from our spinning CD players to dancing Santa Claus dolls. Related Electricity & Magnetism Pages Interactive Java Tutorials: Daniell Cell Interactive Java Tutorials: Simple...

316

Electronic transport and correlations in single magnetic molecule devices.  

E-Print Network [OSTI]

??In this dissertation, we study the most important microscopic aspects that grant molecules such as Single Molecule Magnets (SMMs) their preferential spin direction. We do… (more)

Romero, Javier

2014-01-01T23:59:59.000Z

317

Muon Spin Rotation Studies of Enediynes  

Science Journals Connector (OSTI)

The muon spin plays the role of a nuclear spin, but the spectroscopy proves to be equally sensitive both to muons in electronically diamagnetic environments and to those which experience a hyperfine coupling with paramagnetic electrons, the latter being of importance to the studies involving organic radicals. ... The samples were mounted in a cryostat and exposed to the beam of spin-polarized positive muons while an external magnetic field of 0.2 T was applied transverse to the muon (spin) beam direction. ... To correlate a positron decay with a muon incident on the sample, the experiment was run in time differential mode in which the incoming muon starts a clock at t = 0 and in so doing triggers a gate signal of 10 ?s length (a few muon lifetimes) during which no further muons can be counted. ...

Vasily S. Oganesyan; Andrew N. Cammidge; Gareth A. Hopkins; Fiona M. Cotterill; Ivan D. Reid; Upali A. Jayasooriya

2004-02-17T23:59:59.000Z

318

State Transfer and Spin Measurement  

E-Print Network [OSTI]

We present a Hamiltonian that can be used for amplifying the signal from a quantum state, enabling the measurement of a macroscopic observable to determine the state of a single spin. We prove a general mapping between this Hamiltonian and an exchange Hamiltonian for arbitrary coupling strengths and local magnetic fields. This facilitates the use of existing schemes for perfect state transfer to give perfect amplification. We further prove a link between the evolution of this fixed Hamiltonian and classical Cellular Automata, thereby unifying previous approaches to this amplification task. Finally, we show how to use the new Hamiltonian for perfect state transfer in the, to date, unique scenario where total spin is not conserved during the evolution, and demonstrate that this yields a significantly different response in the presence of decoherence.

A. Kay

2006-04-21T23:59:59.000Z

319

Magnetism of nickel  

Science Journals Connector (OSTI)

A previously developed theory of the magnetism of iron, based upon notion of a randomized exchange field, has now been applied to calculate the properties of nickel. We obtained a Curie temperature of 1200 K, about twice the observed value. The magnetization curve, the paramagnetic susceptibility (a Curie-Weiss law), and the distribution of spin lengths are also calculated. Both similarities and differences from the results of the iron calculations are noted.

J. Hubbard

1981-06-01T23:59:59.000Z

320

An electron spin resonance investigation of irradiated potassium chloride crystals doped with sodium nitroprusside  

E-Print Network [OSTI]

's, attention was turned. to a large extent to the topic of organic n-radicals. Electron spin resonance was first observed in free rad1cals in 1907 by Kozyrev and. Salikhov ) in the case of pentaphenyclopentadienyl. In solid penta... radical possesses mainly spin magnetism in accordance with measurements of its static magnetic susceptibility. In l949 a systematic study of electron spin resonance spectra in free radicals was initiated, i. e. molecules in which at least one electron...

Mayers, Richard Ralph

2012-06-07T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

Electric-field-induced spin depolarization in graphene quantum dots  

Science Journals Connector (OSTI)

We study the effect of the in-plane electric field on the magnetic properties of charge-neutral triangular zigzag graphene quantum dot (GQD) by using the mean-field Hubbard Hamiltonian. Our calculated results show that spin depolarization begins to occur when the electric field is beyond some critical value. The spin-density distribution is more concentrated in the region of the GQDs with smaller electrostatic potential. This phenomenon is attributed to the competition between the many-body electron-electron interaction and the external electrostatic potential. Numerical results also show that the total spin of larger GQDs are easier to depolarize than the total spin of smaller GQDs. Moreover, the spin of GQDs with weak edge disorder still respond to an electric field but in a more irregular way. Our findings provide a path to electrically tuning the magnetic properties of GQDs.

Wen-Long Ma and Shu-Shen Li

2012-07-30T23:59:59.000Z

322

Journal of Magnetism and Magnetic Materials 272276 (2004) e1333e1334 Non-local Hall resistance measured in submicron-scale  

E-Print Network [OSTI]

succeeded in detecting the spin- accumulation signal in the normal metal by the non- local spin-valve-related phenomenon like a spin-valve effect. When the spin-polarized electrons accumulate in a non-magnetic metal coefficient of 8:40 Ã? 10Ã?11 A=cm3 ; indicating the effect of the stray filed from the ferromagnetic layer

Otani, Yoshichika

323

Nuclear Magnetic Resonance Investigations of Human Neoplastic and Abnormal Nonneoplastic Tissues  

Science Journals Connector (OSTI)

...Tumor Detection by Nuclear Magnetic Resonance. Science. ///: 1151 1153, 1971...Potassium (39K) Nuclear Magnetic Reso nance: Spin Signatures...Cancer in Vivo by Nuclear Magnetic- Resonance. Science. 178: 1288 1290. 1972...

Joseph C. Eggleston; Leon A. Saryan; and Donald P. Hollis

1975-05-01T23:59:59.000Z

324

Slow Magnetic Relaxation in Multinuclear Coordination Clusters and Low-Coordinate Transition Metal Complexes  

E-Print Network [OSTI]

N. ; Mallah, T. , Synthesis of Single–Molecule Magnets UsingMetallocyanates. In Single–Molecule Magnets and Related1.2. Multinuclear Single-Molecule Magnets and the Spin-

Zadrozny, Joseph Mercer

2013-01-01T23:59:59.000Z

325

Magnetism in bcc cobalt  

Science Journals Connector (OSTI)

Local-spin-density-approximation-based calculations, performed using a general-potential linearized augmented-plane-wave method, are presented for bcc Co. The ground-state properties and magnetization energies are reported. It is found that the moment is strongly suppressed in constrained antiferromagnetic calculations, indicating that a local-moment picture is less appropriate for this material than for bcc iron.

D. J. Singh

1992-02-01T23:59:59.000Z

326

Electrical control of flying spin precession in chiral 1D edge states  

SciTech Connect (OSTI)

Electrical control and detection of spin precession are experimentally demonstrated by using spin-resolved edge states in the integer quantum Hall regime. Spin precession is triggered at a corner of a biased metal gate, where electron orbital motion makes a sharp turn leading to a nonadiabatic change in the effective magnetic field via spin-orbit interaction. The phase of precession is controlled by the group velocity of edge-state electrons tuned by gate bias voltage: Spin-FET-like coherent control of spin precession is thus realized by all-electrical means.

Nakajima, Takashi; Komiyama, Susumu [Department of Basic Science, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902 (Japan); Lin, Kuan-Ting [Department of Physics, National Tsing Hua University, Hsinchu, Taiwan (China)

2013-12-04T23:59:59.000Z

327

Quantum field theory solution for a short-range interacting SO(3) quantum spin-glass  

E-Print Network [OSTI]

We study the quenched disordered magnetic system, which is obtained from the 2D SO(3) quantum Heisenberg model, on a square lattice, with nearest neighbors interaction, by taking a Gaussian random distribution of couplings centered in an antiferromagnetic coupling, $\\bar J>0$ and with a width $\\Delta J$. Using coherent spin states we can integrate over the random variables and map the system onto a field theory, which is a generalization of the SO(3) nonlinear sigma model with different flavors corresponding to the replicas, coupling parameter proportional to $\\bar J$ and having a quartic spin interaction proportional to the disorder ($\\Delta J$). After deriving the CP$^1$ version of the system, we perform a calculation of the free energy density in the limit of zero replicas, which fully includes the quantum fluctuations of the CP$^1$ fields $z_i$. We, thereby obtain the phase diagram of the system in terms of ($T, \\bar J, \\Delta J$). This presents an ordered antiferromagnetic (AF) phase, a paramagnetic (PM) phase and a spin-glass (SG) phase. A critical curve separating the PM and SG phases ends at a quantum critical point located between the AF and SG phases, at T=0. The Edwards-Anderson order parameter, as well as the magnetic susceptibilities are explicitly obtained in each of the three phases as a function of the three control parameters. The magnetic susceptibilities show a Curie-type behavior at high temperatures and exhibit a clear cusp, characteristic of the SG transition, at the transition line. The thermodynamic stability of the phases is investigated by a careful analysis of the Hessian matrix of the free energy. We show that all principal minors of the Hessian are positive in the limit of zero replicas, implying in particular that the SG phase is stable.

C. M. S. da Conceição; E. C. Marino

2009-03-02T23:59:59.000Z

328

SPIN-TORQUE IN SYSTEMS WITH INHOMOGENEOUS MAGETIZATION  

SciTech Connect (OSTI)

The work performed during the grant period focused on the phenomenon of spin-transfer torque. This is a quantum mechanical effect whereby the angular momentum of conduction electrons is transferred to the magnetization of ferromagnetic structures. Our work on this subject began with phenomenological drift-diffusion and Landau-Lifshitz-Gilbert equations to demonstrate unambiguously that unpolarized current flow from a nonmagnet into a ferromagnet can produce a precession-type instability of the magnetization. We then used Boltzmann calculations appropriate to spin-valve type magnetic heterostructures composed of a non-magnetic thin film sandwiched between two thin film layers with uniform magnetization. Perhaps our most important paper dealt with quantum and semi-classical calculations of spin-transfer torque in systems with domain walls and other inhomogeneous distributions of magnetization. The latter work caused us to suggest that the Landau-Lifshitz approach to magnetic damping provided a clearer picture of the physics than the more popular (but formally equivalent) Gilbert approach to damping. Finally, we returned to our Boltzmann calculations and made a serious effort to analyze experimental data on current-induced magnetization in switching in magnetic spin-valve structures. Our work was part of a world-wide effort to study and harness the transport of the electron's spin and was one of the first sustained theoretical efforts in this direction in the United States. The payoff is just now being seen. In November of 2012, the Everspin Corporation announced the release of the first commercial spin-torque magnetoresistive random access memory.

Zangwill, Andrew [Georgia Institute of Technology

2013-04-23T23:59:59.000Z

329

Magnetism and superconductivity in Sr YRu Cu O and magnetism in Ba GdRu Cu O  

Science Journals Connector (OSTI)

We report magnetization, surface resistance ( ), and electron spin resonance (ESR) for non-superconducting Ba2GdRu1-uCuuO6, and find that all three magnetic ions (Gd, Ru, and Cu...

H.A. Blackstead; John D. Dow; D.R. Harshman…

2000-06-01T23:59:59.000Z

330

Magnetic Catalysis vs Magnetic Inhibition  

E-Print Network [OSTI]

We discuss the fate of chiral symmetry in an extremely strong magnetic field B. We investigate not only quark fluctuations but also neutral meson effects. The former would enhance the chiral-symmetry breaking at finite B according to the Magnetic Catalysis, while the latter would suppress the chiral condensate once B exceeds the scale of the hadron structure. Using a chiral model we demonstrate how neutral mesons are subject to the dimensional reduction and the low dimensionality favors the chiral-symmetric phase. We point out that this effect, the Magnetic Inhibition, can be a feasible explanation for recent lattice-QCD data indicating the decreasing behavior of the chiral-restoration temperature with increasing B.

Kenji Fukushima; Yoshimasa Hidaka

2012-09-06T23:59:59.000Z

331

Sharp Phase Transitions in a Small Frustrated Network of Trapped Ion Spins  

Science Journals Connector (OSTI)

Sharp quantum phase transitions typically require a large system with many particles. Here we show that, for a frustrated fully connected Ising spin network represented by trapped atomic ions, the competition between different spin orders leads to rich phase transitions whose sharpness scales exponentially with the number of spins. This unusual finite-size scaling behavior opens up the possibility of observing sharp quantum phase transitions in a system of just a few trapped ion spins.

G.-D. Lin; C. Monroe; L.-M. Duan

2011-06-08T23:59:59.000Z

332

Sharp phase transitions in a small frustrated network of trapped ion spins  

E-Print Network [OSTI]

Sharp quantum phase transitions typically require a large system with many particles. Here we show that for a frustrated fully-connected Ising spin network represented by trapped atomic ions, the competition between different spin orders leads to rich phase transitions whose sharpness scales exponentially with the number of spins. This unusual finite-size scaling behavior opens up the possibility of observing sharp quantum phase transitions in a system of just a few trapped ion spins.

G. -D. Lin; C. Monroe; L. -M. Duan

2010-11-25T23:59:59.000Z

333

Magnetic Edge States in Graphene  

E-Print Network [OSTI]

Magnetic confinement in graphene has been of recent and growing interest because its potential applications in nanotechnology. In particular, the observation of the so called magnetic edge states in graphene has opened the possibility to deepen into the generation of spin currents and its applications in spintronics. We study the magnetic edge states of quasi-particles arising in graphene monolayers due to an inhomogeneous magnetic field of a magnetic barrier in the formalism of the two-dimensional massless Dirac equation. We also show how the solutions of such states in each of both triangular sublattices of the graphene are related through a supersymmetric transformation in the quantum mechanical sense.

Gabriela Murguia

2010-08-29T23:59:59.000Z

334

Spin waves throughout the Brillouin zone and magnetic exchange coupling in the ferromagnetic metallic manganites La{sub 1-x}Ca{sub x}MnO{sub 3} (x=0.25,0.30)  

SciTech Connect (OSTI)

Using time-of-flight and triple-axis inelastic neutron spectroscopy, we determine spin-wave excitations throughout the Brillouin zone for ferromagnetic manganites La{sub 1-x}Ca{sub x}MnO{sub 3} (x=0.25,0.3) in their low-temperature metallic states. While spin-wave excitations in the long-wavelength limit (spin stiffness D) have similar values for both compounds, the excitations near the Brillouin-zone boundary of La{sub 0.7}Ca{sub 0.3}MnO{sub 3} are considerably softened in all symmetry directions compared to that of La{sub 0.75}Ca{sub 0.25}MnO{sub 3}. A Heisenberg model with the nearest neighbor and the fourth neighbor exchange interactions can describe the overall dispersion curves fairly well. We compare the data with various theoretical models describing the spin excitations of ferromagnetic manganites.

Ye, F. [Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393 (United States); Dai Pengcheng [Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200 (United States); Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393 (United States); Fernandez-Baca, J. A. [Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393 (United States); Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200 (United States); Adroja, D. T.; Perring, T. G. [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX (United Kingdom); Tomioka, Y. [Correlated Electron Research Center (CERC), Tsukuba 305-0046 (Japan); Tokura, Y. [Correlated Electron Research Center (CERC), Tsukuba 305-0046 (Japan); Department of Applied Physics, University of Tokyo, Tokyo 113-8656 (Japan)

2007-04-01T23:59:59.000Z

335

Strange correlations in spin-1 Heisenberg antiferromagnets  

E-Print Network [OSTI]

We study the behavior of the recently proposed "strange correlator" [Phys. Rev. Lett. {\\bf 112}, 247202 (2014)] in spin-1 Heisenberg antiferromagnetic chains with uniaxial single-ion anisotropy. Using projective quantum Monte Carlo, we are able to directly access the strange correlator in a variety of phases, as well as to examine its critical behavior at the quantum phase transition between trivial and non-trivial symmetry protected topological phases. After finding the expected long-range behavior in these two symmetry conserving phases, we go on to verify the topological nature of two-leg and three-leg spin-1 Heisenberg antiferromagnetic ladders. This demonstrates the power of the strange correlator in distinguishing between trivial and non-trivial symmetry protected topological phases.

Wierschem, Keola

2014-01-01T23:59:59.000Z

336

Nature of the quantum spin correlations through the superconducting?normal phase transition in electron-doped superconducting Pr0.88LaCe0.12CuO4  

SciTech Connect (OSTI)

We use neutron scattering and specific heat measurements to relate the response of the spin fluctuations and static antiferromagnetic (AF) order to the superconductivity in the electron-doped high-transition-temperature superconductor, Pr{sub .88}LaCe{sub .12}CuO{sub 4-{delta}} (PLCCO) (T{sub c} = 24 K), as the system is tuned via a magnetic field applied beyond the upper critical field (H{sub c2}) and driven into the normal state. The strength of the collective magnetic excitation commonly termed 'resonance' decreases smoothly with increasing field and vanishes in the normal state, paralleling the behavior of the superconducting condensation energy. The suppression of superconductivity is accompanied by a smooth reduction in the very low energy spin fluctuations, and the concomitant emergence of static AF order. Our results suggest an intimate connection between the resonance and the superconducting condensation energy.

Dai, Pengcheng [ORNL; Wilson, Stephen D. [University of Tennessee, Knoxville (UTK); Li, Shiliang [University of Tennessee, Knoxville (UTK); Wen, H. H. [Chinese Academy of Sciences

2008-01-01T23:59:59.000Z

337

Ultrasound and nuclear magnetism in bulk and confined liquid sup 3 He  

SciTech Connect (OSTI)

Two different experiments on liquid {sup 3}He in open and confined geometries were performed. In the first, the attenuation and velocity of 5 MHz ultra-sound were measured in both the bulk normal and superfluid phases as a function of temperature (0.3 to 30 mK) and pressure (0.3 to 34 bars). The zero temperature limiting behavior was observed in the B-phase superfluid at temperatures below T/{Tc} = 0.4. The velocity was found to return to its ordinary first-sound value as was theoretically expected. Using precise measurements of the difference between the zero-and first-sound velocities, the second symmetric Landau parameter, F{sub 2}{sup s}, was deduced as a function of pressure. In the other experiment, nuclear magnetic resonance (NMR) was used to probe the magnetic susceptibility, {chi}, transverse spin dephasing time, {tau}{sub 2}, and spin-lattice relaxation time, {tau}{sub 1}. Measurements were performed as a function of temperature (0.3 mK to 2K), pressure (0 to 9 bars), and frequency (231,345,462,692, and 924 kHz). The magnetic susceptibility was found to obey a Curie-Weiss law with a pressure-dependent ferromagnetic Weiss temperature. The spin dephasing time was found to be a strong function of temperature at low temperature, with its slope determined by the resonance frequency. This frequency dependence of {tau}{sub 2} was exploited, using a simple model, to obtain the true spin-spin relaxation time, {tau}{sub 2}, as a function of temperature. This was found to obey the same inverse temperature dependence as the susceptibility, diverging at the extrapolated ferromagnetic transition.

Engel, B.N.

1988-01-01T23:59:59.000Z

338

Brownian motion and magnetism  

Science Journals Connector (OSTI)

We present an interesting connection between Brownian motion and magnetism. We use this to determine the distribution of areas enclosed by the path of a particle diffusing on a sphere. In addition, we find a bound on the free energy of an arbitrary system of spinless bosons in a magnetic field. The work presented here is expected to shed light on polymer entanglement, depolarized light scattering, and magnetic behavior of spinless bosons.

Supurna Sinha and Joseph Samuel

1994-11-01T23:59:59.000Z

339

The Glass Transition in Fluids with Magnetic Interactions  

E-Print Network [OSTI]

We study the glass transition in fluids where particles are endowed with spins, such that magnetic and positional degrees of freedom are coupled. Novel results for slowing down in the spin time-correlation functions are described, and the effects of magnetic fields on the glass transition are studied. Aging effects in such systems and the corresponding data collapse are presented and discussed.

Ricardo Gutierrez; Bhaskar Sen Gupta; Itamar Procaccia

2014-06-15T23:59:59.000Z

340

Electronic behavior of highly correlated metals  

SciTech Connect (OSTI)

This thesis addresses the question of the strongly interacting many-body problem: that is, systems where the interparticle correlations are so strong as to defy perturbative approaches. These subtle correlations occur in narrow band materials, such as the lanthanides and actinides, wherein the f-electrons are so localized that a variety of new phenomena, including intermediate-valence and heavy-fermionic behavior, may occur. As well, one has the alloying problem, where local interactions are paramount in determining the overall behavior. The technique employed in dealing with these systems is the Small Cluster method, wherein the full many-body Hamiltonian for a small grouping of atoms, coupled with periodic boundary conditions, is solved exactly. This is tantamount to solving a bulk crystal at the high points of symmetry in the Brillouin Zone. The mathematical overhead is further reduced by employing the full space group and spin symmetries. By its very nature, the Small Cluster method is well able to handle short-range interactions, as well as the combinatorial complexity of the many-body problem, on an equal footing. The nature of long-range order and phase transition behavior cannot be incorporated, but sometimes clues as to their origin can be discerned. The calculations presented include: a two-band Anderson model for an intermediate-valence system, wherein photoemission and fluctuation behavior is examined; a single-band Hubbard model for a ternary alloy system, such as copper-silver-gold; and a Hubbard model for a heavy- fermion system, wherein Fermi surface, transport, magnetic and superconducting properties are discussed. 148 refs., 31 figs., 24 tabs.

Reich, A.

1988-10-01T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

Magnetism of nanosized metallic particles  

Science Journals Connector (OSTI)

The magnetism of a small cluster of magnetic atoms at finite temperatures is numerically investigated. The evolution of the system towards thermal equilibrium is studied, and the possibility of occurrence of vortexlike excitations in the arrangement of the magnetic moments within the cluster is pointed out. The magnetization curve as a function of temperature, of a small magnetic particle, suggests that magnetic clusters in granular metals are not saturated even at room temperature. The relevance of the present results to the understanding of the magnetic behavior of granular metals is discussed.

P. Vargas; J. d’Albuquerque e Castro; D. Altbir

1999-09-01T23:59:59.000Z

342

Development and characterization of the magnetic plasmatron  

E-Print Network [OSTI]

The purpose of this thesis is to investigate the plausibility of developing a low current plasmatron fuel reformer that utilizes magnetic fields to hydrodynamically induce spin of the arc discharge. The proof of principle, ...

Anziani, Felipe Rene, 1981-

2004-01-01T23:59:59.000Z

343

First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments  

Science Journals Connector (OSTI)

A method to map spin-resolved electron distribution from combined polarized neutron and X-ray diffraction is described and applied for the first time to a molecular magnet and it is shown that spin up density is 5% more contracted than spin down density.

Deutsch, M.

2014-04-14T23:59:59.000Z

344

Methods for characterizing magnetic footprints of perpendicular magnetic recording writer heads  

SciTech Connect (OSTI)

In this work, the magnetic footprints, along with some of its dynamic features in recording process, of perpendicular magnetic recording writer heads have been characterized by using three different techniques. Those techniques are the spin-stand stationary footprint technique, the spin-stand dynamic footprint technique, and the coherent writing technique combined with magnetic force microscope imaging method. The characteristics of those techniques have been compared to one another. It was found experimentally that the spin-stand stationary method could not precisely catch some peculiar recording dynamics of the write heads in certain conditions. The advantages and disadvantages among all those techniques are also examined and discussed in detail.

Li, Shaoping, E-mail: shaoping.li@wdc.com; Lin, Ed; George, Zach; Terrill, Dave; Mendez, H.; Santucci, J.; Yie, Derek [Western Digital Corp., 44100 Osgood Road, Fremont, California 94539 (United States)

2014-05-07T23:59:59.000Z

345

Spintronic transport of a non-magnetic molecule between magnetic electrodes  

SciTech Connect (OSTI)

The spintronic transport properties of a junction system composed of a non-magnetic molecule sandwiched between ferromagnetic metal electrodes are investigated theoretically using a non-equilibrium Green's function method based on density functional theory. It is revealed that in such a system, the molecular magnetic properties induced by hybridization with the magnetic electrodes play a crucial role. Alignment of the induced molecular spin-split levels is strongly related to the spin injection and tunneling magneto-resistance effects. It is found that in the system with weaker molecule-electrode interaction, stronger spintronic effects of the spin injection and tunneling magneto-resistance are observed.

Kondo, Hisashi, E-mail: kondo@tokyo.rist.or.jp [Institute of Industrial Science, University of Tokyo, Meguro, Tokyo 153-8505 (Japan)] [Institute of Industrial Science, University of Tokyo, Meguro, Tokyo 153-8505 (Japan); Ohno, Takahisa, E-mail: OHNO.Takahisa@nims.go.jp [Computational Materials Science Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan) [Computational Materials Science Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan); Institute of Industrial Science, University of Tokyo, Meguro, Tokyo 153-8505 (Japan)

2013-12-02T23:59:59.000Z

346

Supplementary Information for `Spintronic magnetic anisotropy'  

E-Print Network [OSTI]

-filtering effect 19 G. On-demand bistability: writing and storing spin 20 H. Magnetic switching of spintronic of anisotropy by analysing the trans- port properties of a high-spin quantum dot embedded between two Heisenberg interaction K energy of a single electron occupying

Loss, Daniel

347

Cylindrical Ising nanowire in an oscillating magnetic field and dynamic compensation temperature  

Science Journals Connector (OSTI)

Abstract The nonequilibrium magnetic properties of a spin-1/2 cylindrical Ising nanowire system with core/shell in an oscillating magnetic field are studied by using a mean-field approach based on the Glauber-type stochastic dynamics (DMFT). We employ the Glauber-type stochastic dynamics to construct set of the coupled mean-field dynamic equations. First, we study the temperature dependence of the dynamic order parameters to characterize the nature of the phase transitions and to obtain the dynamic phase transition points. Then, we investigate the temperature dependence of the total magnetization to find the dynamic compensation points as well as to determine the type of behavior. The phase diagrams in which contain the paramagnetic, ferromagnetic, ferrimagnetic, partially nonmagnetic, surface fundamental phases and tree mixed phases as well as reentrant behavior are presented in the reduced magnetic field amplitude and reduced temperature plane. According to values of Hamiltonian parameters, the compensation temperatures, or the N-, Q-, P-, R-, S-type behaviors.

Ersin Kantar; Mehmet Erta?

2014-01-01T23:59:59.000Z

348

Magnetization dynamics of cobalt grown on graphene  

SciTech Connect (OSTI)

Ferromagnetic resonance (FMR) spin pumping is a rapidly growing field which has demonstrated promising results in a variety of material systems. This technique utilizes the resonant precession of magnetization in a ferromagnet to inject spin into an adjacent non-magnetic material. Spin pumping into graphene is attractive on account of its exceptional spin transport properties. This article reports on FMR characterization of cobalt grown on chemical vapor deposition graphene and examines the validity of linewidth broadening as an indicator of spin pumping. In comparison to cobalt samples without graphene, direct contact cobalt-on-graphene exhibits increased FMR linewidth—an often used signature of spin pumping. Similar results are obtained in Co/MgO/graphene structures, where a 1?nm MgO layer acts as a tunnel barrier. However, magnetometry, magnetic force microscopy, and Kerr microscopy measurements demonstrate increased magnetic disorder in cobalt grown on graphene, perhaps due to changes in the growth process and an increase in defects. This magnetic disorder may account for the observed linewidth enhancement due to effects such as two-magnon scattering or mosaicity. As such, it is not possible to conclude successful spin injection into graphene from FMR linewidth measurements alone.

Berger, A. J.; White, S. P.; Adur, R.; Pu, Y.; Hammel, P. C., E-mail: hammel@physics.osu.edu [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Amamou, W. [Department of Physics and Astronomy, University of California, Riverside, California 92521 (United States); Kawakami, R. K. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Physics and Astronomy, University of California, Riverside, California 92521 (United States)

2014-05-07T23:59:59.000Z

349

Nuclear magnetism in a metal  

Science Journals Connector (OSTI)

We discuss the ordered-state properties of an assembly of nuclear spins, interacting via a classical dipolar and conduction-electron-mediated exchange interaction. The ground-state spin arrangement can be found by using a continuum model which casts light on the considerable degeneracy of the ground state. We have studied the effect of a magnetic field and have derived a set of equations for spin dynamics. We also discuss the implications of these results in specific examples such as Pt, Tl, Na, and Cu.

P. Kumar; J. Kurkijarvi; A. S. Oja

1986-01-01T23:59:59.000Z

350

Spin coating apparatus  

DOE Patents [OSTI]

A spin coating apparatus requires less cleanroom air flow than prior spin coating apparatus to minimize cleanroom contamination. A shaped exhaust duct from the spin coater maintains process quality while requiring reduced cleanroom air flow. The exhaust duct can decrease in cross section as it extends from the wafer, minimizing eddy formation. The exhaust duct can conform to entrainment streamlines to minimize eddy formation and reduce interprocess contamination at minimal cleanroom air flow rates.

Torczynski, John R. (Albuquerque, NM)

2000-01-01T23:59:59.000Z

351

Nuclear Spins in a Nanoscale Device for Quantum Information Processing  

E-Print Network [OSTI]

Coherent oscillations between any two levels from four nuclear spin states of I=3/2 have been demonstrated in a nanometre-scale NMR semiconductor device, where nuclear spins are all-electrically controlled. Using this device, we discuss quantum logic operations on two fictitious qubits of the I=3/2 system, and propose a quantum state tomography scheme based on the measurement of longitudinal magnetization, $M_z$.

S. K. Ozdemir; A. Miranowicz; T. Ota; G. Yusa; N. Imoto; Y. Hirayama

2006-12-29T23:59:59.000Z

352

On geometry influence on the behavior of a quantum mechanical scalar particle with intrinsic structure in external magnetic and electric fields  

E-Print Network [OSTI]

Relativistic theory of the Cox's scalar not point-like particle with intrinsic structure is developed on the background of arbitrary curved space-time. It is shown that in the most general form, the extended Proca-like tensor first order system of equations contains non minimal interaction terms through electromagnetic tensor F_{\\alpha \\beta} and Ricci tensor R_{\\alpha \\beta}. In relativistic Cox's theory, the limiting procedure to non-relativistic approximation is performed in a special class of curved space-time models. This theory is specified in simple geometrical backgrounds: Euclid's, Lobachevsky's, and Rie\\-mann's. Wave equation for the Cox's particle is solved exactly in presence of external uniform magnetic and electric fields in the case of Minkowski space. Non-trivial additional structure of the particle modifies the frequency of a quantum oscillator arising effectively in presence if external magnetic field. Extension of these problems to the case of the hyperbolic Lobachevsky space is examined. In presence of the magnetic field, the quantum problem in radial variable has been solved exactly; the quantum motion in z-direction is described by 1-dimensional Schr\\"{o}dinger-like equation in an effective potential which turns out to be too difficult for analytical treatment. In the presence of electric field, the situation is similar. The same analysis has been performed for spherical Riemann space model.

O. V. Veko; K. V. Kazmerchuk; E. M. Ovsiyuk; V. V. Kisel; V. M. Red'kov

2014-11-07T23:59:59.000Z

353

The Behavioral Development of Two Beluga Calves During the First Year of Life  

E-Print Network [OSTI]

and tossing water, making bubbles), motor play (e.g. ,motor behavior, such as a vertical spin at the waterwater by creating bubble rings and vortices. Motor play

Hill, Heather M.

2009-01-01T23:59:59.000Z

354

Refocusing dipolar interactions between electronic spins of donors in silicon  

E-Print Network [OSTI]

We note the existence of a set of magnetic field values where a simple Hahn echo sequence refocuses the dynamics of the full dipolar interaction, for spin systems of electron donors in silicon. As the refocussing occurs for both arbitrary coupling strengths and arbitrary times, these dipolar refocusing points (DRPs) offer new possibilities for regulating entanglement due to the always-on spin dipolar interaction. While the experimental effects of DRPs will be strongly diluted in the measured coherences of thermal (unpolarized) spin ensembles, we investigate possible signatures in coherence decays arising from a study of the combined effects of decoherence arising from instantaneous diffusion and direct flip-flops

T. S. Monteiro

2014-12-08T23:59:59.000Z

355

Nuclear spin qubits in a trapped-ion quantum computer  

E-Print Network [OSTI]

Physical systems must fulfill a number of conditions to qualify as useful quantum bits (qubits) for quantum information processing, including ease of manipulation, long decoherence times, and high fidelity readout operations. Since these conditions are hard to satisfy with a single system, it may be necessary to combine different degrees of freedom. Here we discuss a possible system, based on electronic and nuclear spin degrees of freedom in trapped ions. The nuclear spin yields long decoherence times, while the electronic spin, in a magnetic field gradient, provides efficient manipulation, and the optical transitions of the ions assure a selective and efficient initialization and readout.

M. Feng; Y. Y. Xu; F. Zhou; D. Suter

2009-04-26T23:59:59.000Z

356

Zero sound modes of dilute Fermi gases with arbitrary spin  

Science Journals Connector (OSTI)

Motivated by the recent success of optical trapping of alkali-metal bosons, we have studied the zero sound modes of dilute Fermi gases with arbitrary spin-f, which are spin-S excitations (0<~S<~2f). The dispersion of the mode (S) depends on a single Landau parameter F(S), which is related to the scattering lengths of the system through a simple formula. Measurement of (even a subset of) these modes in finite magnetic fields will enable one to determine all the interaction parameters of the system.

S.-K. Yip and Tin-Lun Ho

1999-06-01T23:59:59.000Z

357

Microscopic magnetic properties of an oxygen-doped Tb-Fe thin film by magnetic Compton scattering  

SciTech Connect (OSTI)

The magnetic Compton scattering of a Tb{sub 32}Fe{sub 55}O{sub 13} film was measured in order to investigate the microscopic magnetization processes (i.e., the spin moment, orbital moment, and element specific moments). The trend of the spin magnetic moment was the same as that of the total magnetic moment but opposite to the orbital magnetic moment. In the low magnetic field region, the magnetic moments were not perfectly aligned perpendicular to the film surface, and the perpendicular components were found to mainly arise from the magnetic moment of Tb. Oxygen atoms hinder long range magnetic interaction and hence also affect the magnetization process of the magnetic moments of Tb and Fe.

Agui, Akane, E-mail: agui@spring8.or.jp [Quantum Beam Science Directorate, Japan Atomic Energy Agency, SPring-8, Sayo, Hyogo 679-5148 (Japan); Unno, Tomoya; Matsumoto, Sayaka; Suzuki, Kousuke; Sakurai, Hiroshi [Department of Production Science and Technology, Gunma University, Ota, Gunma 373-0057 (Japan); Koizumi, Akihisa [Graduate School of Material Science, University of Hyogo, Kamigori, Hyogo 678-1297 (Japan)

2013-11-14T23:59:59.000Z

358

Ultrafast nuclear spin polarization for isotopes with large nuclear spin  

Science Journals Connector (OSTI)

We theoretically investigate the temporal dynamics of nuclear spin induced by short laser pulses. To realize ultrafast nuclear spin polarization, we coherently excite the hyperfine...

Nakajima, Takashi

2009-01-01T23:59:59.000Z

359

residual magnetism  

Science Journals Connector (OSTI)

The magnetization, i.e., the magnetic polarization, that remains in a magnetized material after all attempts to remove the magnetization have been made. Note: An example of residual magnetization is the magnetiza...

2001-01-01T23:59:59.000Z

360

Status of Spin Physics  

E-Print Network [OSTI]

Fundamental spin physics has made striking progresses in the last years; new ideas, experiments and data interpretations have been proposed and keep emerging. A review of some of the most important issues in the spin structure of nucleons is made and prospects for the future are discussed.

Mauro Anselmino

2001-07-09T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Spin coating of electrolytes  

DOE Patents [OSTI]

Methods for spin coating electrolytic materials onto substrates are disclosed. More particularly, methods for depositing solid coatings of ion-conducting material onto planar substrates and onto electrodes are disclosed. These spin coating methods are employed to fabricate electrochemical sensors for use in measuring, detecting and quantifying gases and liquids.

Stetter, Joseph R. (Naperville, IL); Maclay, G. Jordan (Maywood, IL)

1989-01-01T23:59:59.000Z

362

Magnetism in amorphous transition metals  

Science Journals Connector (OSTI)

Overall features of magnetism in amorphous transition metals have been investigated on the basis of a finite-temperature theory of the local-environment effect. It is shown that the simple ferromagnetism of Fe, Co, and Ni is drastically changed by structural disorder; amorphous transition metals form spin glasses (SG’s) for compositions near amorphous Fe (6.7?N?7.35), ferromagnets for compositions near amorphous Co (7.35?N?9.0), and paramagnetisms for compositions near amorphous Ni (9.0?N?10.0) where N is the number of d electrons. The SG is accompanied by formation of local ferromagnetic clusters for N?7.2, and shows reentrant behavior at the ferromagnetic boundary N?7.35. The ferromagnetism in amorphous transition metals is shown to be well explained by the main-peak position in the noninteracting densities of states. It is found that structural disorder enhances the Curie temperatures (TC) in the range 7.9?N?8.5 as compared with bcc and fcc structures. These results explain recent experimental data for the SG in Fe-rich amorphous alloys and the high TC in amorphous Co-Y alloys, but they are quite different from the early picture obtained for amorphous transition-metal–metalloid alloys.

Y. Kakehashi

1991-05-01T23:59:59.000Z

363

Spin superconductor in ferromagnetic graphene  

Science Journals Connector (OSTI)

We show a spin superconductor in ferromagnetic graphene as the counterpart to the charge superconductor in which a spin-polarized electron-hole pair plays the role of the spin 2(?/2) “Cooper pair” with a neutral charge. We present a BCS-type theory for the spin superconductor. With the “London-type equations” of the super-spin-current density, we show the existence of an electric “Meissner effect” against a spatial varying electric field. We further study a spin superconductor/normal conductor/spin superconductor junction and predict a spin-current Josephson effect.

Qing-feng Sun; Zhao-tan Jiang; Yue Yu; X. C. Xie

2011-12-02T23:59:59.000Z

364

Spin-Chirality-Driven Ferroelectricity on a Perfect Triangular Lattice Antiferromagnet  

SciTech Connect (OSTI)

Magnetic eld (B) variation of the electrical polarization Pc ( c) of the perfect triangular lattice antiferromagnet RbFe(MoO4)2 is examined up to the saturation point of the magnetization for B ? c. Pc is observed only in phases for which chirality is predicted in the in-plane magnetic structures. No strong anomaly is observed in Pc at the eld at which the spin modulation along the c axis, and hence the spin helicity, exhibits a discontinuity to the commensurate state. These results indicate that the ferroelectricity in this compound originates predominantly from the spin chirality, the explanation of which would require a new mechanism for magnetoferroelectricity. The obtained eld-temperature phase diagrams of ferroelectricity well agree with those theoretically predicted for the spin chirality of a Heisenberg spin triangular lattice antiferromagnet.

Mitamura, H. [University of Tokyo, Japan; Watanuki, R. [Yokohama National University; Kaneko, Koji [Japan Atomic Energy Agency (JAEA); Onozaki, N. [Yokohama National University; Amou, Y. [Yokohama National University; Kittaka, S. [University of Tokyo, Japan; Kobayashi, Riki [ORNL; Shimura, Y. [University of Tokyo, Japan; Yamamoto, I. [Yokohama National University; Suzuki, K. [Yokohama National University; Chi, Songxue [ORNL; Sakakibara, T. [University of Tokyo, Japan

2014-01-01T23:59:59.000Z

365

Quantitative study of spin noise spectroscopy in a classical gas of {sup 41}K atoms  

SciTech Connect (OSTI)

We present a general derivation of the electron spin noise power spectrum in alkali gases as measured by optical Faraday rotation, which applies to both classical gases at high temperatures as well as ultracold quantum gases. We show that the spin-noise power spectrum is determined by an electron spin-spin correlation function, and we find that measurements of the spin-noise power spectra for a classical gas of {sup 41}K atoms are in good agreement with the predicted values. Experimental and theoretical spin noise spectra are directly and quantitatively compared in both longitudinal and transverse magnetic fields up to the high magnetic-field regime (where Zeeman energies exceed the intrinsic hyperfine energy splitting of the {sup 41}K ground state)

Mihaila, Bogdan [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Crooker, Scott A.; Rickel, Dwight G. [National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Blagoev, Krastan B.; Smith, Darryl L. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Littlewood, Peter B. [Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE (United Kingdom)

2006-10-15T23:59:59.000Z

366

Realization of Spin Gapless Semiconductors: The Heusler Compound Mn2CoAl  

Science Journals Connector (OSTI)

Recent studies have reported an interesting class of semiconductor materials that bridge the gap between semiconductors and half-metallic ferromagnets. These materials, called spin gapless semiconductors, exhibit a band gap in one of the spin channels and a zero band gap in the other and thus allow for tunable spin transport. Here, we report the first experimental verification of the spin gapless magnetic semiconductor Mn2CoAl, an inverse Heusler compound with a Curie temperature of 720 K and a magnetic moment of 2?B. Below 300 K, the compound exhibits nearly temperature-independent conductivity, very low, temperature-independent carrier concentration, and a vanishing Seebeck coefficient. The anomalous Hall effect is comparatively low, which is explained by the symmetry properties of the Berry curvature. Mn2CoAl is not only suitable material for room temperature semiconductor spintronics, the robust spin polarization of the spin gapless semiconductors makes it very promising material for spintronics in general.

Siham Ouardi; Gerhard H. Fecher; Claudia Felser; Jürgen Kübler

2013-03-05T23:59:59.000Z

367

Quantitative study of spin noise spectroscopy in a classical gas of K41 atoms  

Science Journals Connector (OSTI)

We present a general derivation of the electron spin noise power spectrum in alkali gases as measured by optical Faraday rotation, which applies to both classical gases at high temperatures as well as ultracold quantum gases. We show that the spin-noise power spectrum is determined by an electron spin-spin correlation function, and we find that measurements of the spin-noise power spectra for a classical gas of K41 atoms are in good agreement with the predicted values. Experimental and theoretical spin noise spectra are directly and quantitatively compared in both longitudinal and transverse magnetic fields up to the high magnetic-field regime (where Zeeman energies exceed the intrinsic hyperfine energy splitting of the K41 ground state).

Bogdan Mihaila; Scott A. Crooker; Dwight G. Rickel; Krastan B. Blagoev; Peter B. Littlewood; Darryl L. Smith

2006-10-30T23:59:59.000Z

368

New Model for Amorphous Magnetism  

Science Journals Connector (OSTI)

We propose a new model for magnetism in an amorphous material. The model is particularly appropriate for rare-earth compounds such as TbF2. It is a Heisenberg model in which each ionic spin is subjected to a local anisotropy field of random orientation. We discuss the magnetic properties of two simple ionic configurations, and show that the model is in qualitative agreement with the experimental data.

R. Harris; M. Plischke; M. J. Zuckermann

1973-07-16T23:59:59.000Z

369

Two-Body Nuclear Interaction, consistent, within the Limits of a Single Configuration, with the Spin and Magnetic Moment of the Ground-States of Lithium-6, Boron-10 and Lithium-7  

Science Journals Connector (OSTI)

... within this small range), one obtains, also, agreement with the magnetic moments of boron-10 and lithium-7, again neglecting the contribution to these moments due to M12. It ...

J. P. ELLIOTT; H. A. JAHN

1951-01-06T23:59:59.000Z

370

Hysteretic Optimization For Spin Glasses  

E-Print Network [OSTI]

The recently proposed Hysteretic Optimization (HO) procedure is applied to the 1D Ising spin chain with long range interactions. To study its effectiveness, the quality of ground state energies found as a function of the distance dependence exponent, $\\sigma$, is assessed. It is found that the transition from an infinite-range to a long-range interaction at $\\sigma=0.5$ is accompanied by a sharp decrease in the performance . The transition is signaled by a change in the scaling behavior of the average avalanche size observed during the hysteresis process. This indicates that HO requires the system to be infinite-range, with a high degree of interconnectivity between variables leading to large avalanches, in order to function properly. An analysis of the way auto-correlations evolve during the optimization procedure confirm that the search of phase space is less efficient, with the system becoming effectively stuck in suboptimal configurations much earlier. These observations explain the poor performance that HO obtained for the Edwards-Anderson spin glass on finite-dimensional lattices, and suggest that its usefulness might be limited in many combinatorial optimization problems.

B. Goncalves; S. Boettcher

2007-12-10T23:59:59.000Z

371

Optimization of a microwave resonator cavity to perform electron spin resonance measurements on quantum dots  

E-Print Network [OSTI]

This thesis attempts to improve on an ongoing experiment of detecting electron spin resonance (ESR) on AlGaAs/GaAs lateral quantum dots. The experiment is performed in a 2.5 Tesla magnetic field at temperatures around ...

Burger, Anat

2006-01-01T23:59:59.000Z

372

Femtosecond all-optical modulation of collective spin in the (Ga,Mn)As ferromagnet  

Science Journals Connector (OSTI)

Using a many-body theory, we discuss some fundamental issues of femtomagnetism in magnetic electronic systems. We address the question of how spin may couple to transient optical...

Kapetanakis, Myron D; Wang, Jigang; Perakis, Ilias E

2012-01-01T23:59:59.000Z

373

Superconducting properties of a textured NbN film from N93b NMR relaxation and magnetization measurements  

Science Journals Connector (OSTI)

Primarily motivated by the similarities between the underdoped superconducting cuprates and the granular systems in regards of electric conductivity, phase fluctuations of the order parameter, and nuclear spin-lattice relaxation, a study has been carried out in a NbN(111) textured film at controlled granularity by means of superconducting quantum interference device magnetization and N93b NMR measurements. The Meissner diamagnetism in zero-field-cooling and field-cooling conditions and for different orientation of the magnetic field and the isothermal magnetization curves around the superconducting transition temperature Tc, are studied. N93b spectra and relaxation measurements have been performed for two values of the external magnetic field in parallel and perpendicular geometry, in the temperature range 4–300 K. In the superconducting phase the experimental findings for the textured film are similar to the one in bulk NbN. The nuclear spin-lattice relaxation process is the same as in bulk NbN in the temperature range 50–300 K, confirming a dominant contribution to the density of states at the Fermi energy arising from the Nb 4d band. At variance, on cooling from about 40 K down to Tc (H), the N93b relaxation rate in the film dramatically departs from the expected behavior for the Fermi gas and mimics the opening of a spin gap. The interpretation of the spin-gap opening in terms of depletion in the density of states at the Fermi energy can justify the anomalous temperature behavior of the N93b relaxation rate on approaching Tc (H) from above. The experimental findings suggest the occurrence of superconducting fluctuations (density-of-states term) in one-dimensional regime, coupled to a reduction in the time of flight of the electrons, both effects being related to the granularity. The data also suggest that the spin-gap phase in underdoped cuprates could be connected more to granularity, rather than to exotic mechanisms of magnetic origin.

A. Lascialfari; A. Rigamonti; E. Bernardi; M. Corti; A. Gauzzi; J. C. Villegier

2009-09-09T23:59:59.000Z

374

Electric Dipole Moment of Magnetic Monopole  

E-Print Network [OSTI]

The electric dipole moment of magnetic monopoles with spin is studied in the N=2 supersymmetric gauge theory. The dipole moments of the electric charge distributions, as well as the dipole moments due to the magnetic currents, are calculated. The contribution of charge distribution of the fermion to the gyroelectric ratio is expressed by using zeta(3).

Makoto Kobayashi

2007-03-07T23:59:59.000Z

375

Correlation Functions and Spin  

E-Print Network [OSTI]

The k-electron correlation function of a free chaotic electron beam is derived with the spin degree of freedom taken into account. It is shown that it can be expressed with the help of correlation functions for a polarized electron beam of all orders up to k and the degree of spin polarization. The form of the correlation function suggests that if the electron beam is not highly polarized, observing multi-particle correlations should be difficult. The result can be applied also to chaotic photon beams, the degree of spin polarization being replaced by the degree of polarization.

T. Tyc

2000-06-30T23:59:59.000Z

376

Bias dependence of tunnel magnetoresistance in spin filtering tunnel junctions: Experiment and theory  

Science Journals Connector (OSTI)

A spin filter is a type of magnetic tunnel junction in which only one of the electrodes is magnetic and the insulating barrier is ferro- or ferrimagnetic. We report on spin-dependent transport measurements and their theoretical analysis in epitaxial spin filters integrating a tunnel barrier of the high-Curie-temperature ferrimagnetic spinel NiFe2O4, with half-metallic La2?3Sr1?3MnO3 and Au electrodes. A positive tunnel magnetoresonance of up to ?50% is obtained at low temperature, which we find decreases with bias voltage. In view of these experimental results, we propose a theoretical treatment of the transport properties of spin filters with epitaxial magnetic barriers, based on an elliptical variation of the decay rates within the spin-dependent gaps in analogy with what was calculated for nonmagnetic barrier materials such as MgO or SrTiO3. Whereas the spin filtering efficiency for zero bias is of one sign, we show that this can easily change with bias; the degree of change hinges on the energy variation of the majority and minority spin decay rates of the transmission across the barrier. We point out some shortcomings of approaches based on models in which the transmission is related to spin-dependent barrier heights, and some implications for future experimental and theoretical research on spin filters.

U. Lüders, M. Bibes, S. Fusil, K. Bouzehouane, E. Jacquet, C. B. Sommers, J.-P. Contour, J.-F. Bobo, A. Barthélémy, A. Fert, and P. M. Levy

2007-10-16T23:59:59.000Z

377

Induced effects of the Dzyaloshinskii-Moriya interaction on the thermal entanglement in spin-1/2 Heisenberg chains  

Science Journals Connector (OSTI)

The nearest-neighbor spins in the one-dimensional spin-1/2 XX model with the added Dzyaloshinskii-Moriya (DM) interaction are entangled at zero temperature. In the presence of a transverse magnetic field (TF) they remain entangled up to a quantum critical field, hc. Using the fermionization technique, we have studied the mutual effect of the DM interaction and a TF on the thermal entanglement (TE) in this model. The critical temperature where the entanglement disappears is specified. It is found that the TE in the finite-temperature neighborhood of the quantum critical field shows a scaling behavior with the critical exponent equal to the critical gap exponent. We also argue that thermodynamical properties like the specific heat and the magnetocaloric effect (instead of the usual internal energy and the magnetization) can detect the mentioned quantum entanglement in solid systems. In addition, we suggest a tactic to find all critical temperatures, which is based on the derivative of the entanglement witness with respect to the temperature.

E. Mehran; S. Mahdavifar; R. Jafari

2014-04-08T23:59:59.000Z

378

Whirlpools on the Nanoscale Could Multiply Magnetic Memory  

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

Whirlpools on the Nanoscale Could Whirlpools on the Nanoscale Could Multiply Magnetic Memory Whirlpools on the Nanoscale Could Multiply Magnetic Memory Print Tuesday, 21 May 2013 00:00 Research at the Advanced Light Source may lead to four-bit magnetic cells housed on nanoscale metal disks, instead of the two-bit magnetic domains of standard magnetic memories. In magnetic vortices, parallel electron spins point either clockwise or counterclockwise, while in their crowded centers the spins point either down or up. "From the scientist's point of view, magnetism is about controlling electron spin," says Peter Fischer of the Materials Sciences Division, who leads the work at beamline 6.1.2. Four orientations could provide multibits in a new kind of memory. The next step is to control the states independently and simultaneously.

379

Pressure induced high spin-low spin transition in FeSe superconductor studied by x-ray emission spectroscopy and ab initio calculations  

SciTech Connect (OSTI)

FeSe is a simple binary system in the iron based superconducting family and exhibits a significant pressure induced increase in the superconducting transition temperature (T{sub c}). In addition to pressure effect, spin fluctuations, magnetic ordering, and crystal structure all play vital roles in altering T{sub c}. Even though various experiments and theoretical simulations explain the connection among them and superconductivity, the interplay between these important parameters is still not clearly understood. Here, we report the pressure effect on the spin state of Fe in FeSe superconductor studied using synchrotron x-ray emission spectroscopy at ambient and low temperatures down to 8 K near T{sub c}. Pressure induced high spin to low spin transition was observed at both ambient and low temperatures with continuous suppression of Fe magnetic moments under increasing pressure. The spin transition is closely related to the pressure induced tetragonal to orthorhombic structural transition.

Kumar, Ravhi S.; Zhang, Yi; Xiao, Yuming; Baker, Jason; Cornelius, Andrew; Veeramalai, Sathishkumar; Chow, Paul; Chen, Changfeng; Zhao, Yusheng (UNLV); (CIW)

2011-09-20T23:59:59.000Z

380

Magnetism in hybrid carbon nanostructures: Nanobuds  

Science Journals Connector (OSTI)

The robust magnetic state of recently synthesized hybrid carbon nanostructures, i.e., nanobuds, is predicted through comprehensive spin-polarized density-functional calculations. The effects of chirality, curvature, and topology on the magnetism of nanobuds are scrutinized by detailed electronic structure analysis. The substantial emergent amounts of unpaired spins originate in the presence of carbon radicals introduced by the geometry-induced electronic frustration. The location of radicals is mainly on the nanotube surface within the connecting region with fullerene, rather than surfaces with negative Gaussian curvature. The magnetic nanobuds hold great promise in the field of spintronics owing to their ready accessibility by experimental synthesis and fabrication.

Xi Zhu and Haibin Su

2009-04-02T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Spin waves in a persistent spin-current Fermi liquid  

Science Journals Connector (OSTI)

We report two theoretical results for transverse spin waves, which arise in a system with a persistent spin current. Using Fermi liquid theory, we introduce a spin current in the ground state of a polarized or unpolarized Fermi liquid, and we derive the resultant spin waves using the Landau kinetic equation. The resulting spin waves have a q1 and q1/2 dispersion to leading order for the polarized and unpolarized systems, respectively.

J. D. Feldmann and K. S. Bedell

2010-06-14T23:59:59.000Z

382

Advances in theoretical and physical aspects of spin-spin coupling constants  

Science Journals Connector (OSTI)

Publisher Summary This chapter describes trends of coupling constants on the basis of the concepts commonly used by chemists in the laboratory. With the discovery of nuclear magnetic resonance, four impressive progresses have taken place, both in experimental techniques and in theoretical approaches aimed at understanding the electronic origin of high-resolution nuclear magnetic resonance parameters. The chapter describes the calculation and analysis of spin–spin coupling constants. Intra- and inter-molecular interaction effects on spin–spin coupling constants have also been presented. Ab initio calculations of couplings in small molecules with large basis sets and inclusion of electron correlation effects have reached almost quantitative accuracy. Different types of couplings in different molecular environments have very different computational demands to obtain such accuracy. The use density functional theory (DFT)-based methods for chemical applications have increased exponentially in the past decade and the finite perturbation theory (FPT) approach to calculating the Fermi contact (FC) contribution to different couplings employing a variety of functionals has produced quite promising results. Progress in different experimental techniques helped determine relative signs of coupling constants, which in many cases are now determined routinely. This additional information is a significant improvement in using experimental values to obtain insights into different aspects of molecular electronic structure.

Rubén H. Contreras; Juan E. Peralta; Claudia G. Giribet; Martín C. Ruiz de azúa; Julio C. Facelli

2000-01-01T23:59:59.000Z

383

International Spin Physics 2014 Summary  

E-Print Network [OSTI]

The Stern-Gerlach experiment and the origin of electron spin are described in historical context. SPIN 2014 occurs on the fortieth anniversary of the first International High Energy Spin Physics Symposium at Argonne in 1974. A brief history of the international spin conference series is presented.

Milner, Richard G

2015-01-01T23:59:59.000Z

384

International Spin Physics 2014 Summary  

E-Print Network [OSTI]

The Stern-Gerlach experiment and the origin of electron spin are described in historical context. SPIN 2014 occurs on the fortieth anniversary of the first International High Energy Spin Physics Symposium at Argonne in 1974. A brief history of the international spin conference series is presented.

Richard G. Milner

2015-02-06T23:59:59.000Z

385

Fast deterministic switching in orthogonal spin torque devices via the control of the relative spin polarizations  

SciTech Connect (OSTI)

We model 100 ps pulse switching dynamics of orthogonal spin transfer (OST) devices that employ an out-of-plane polarizer and an in-plane polarizer. Simulation results indicate that increasing the spin polarization ratio, C{sub P}?=?P{sub IPP}/P{sub OPP}, results in deterministic switching of the free layer without over-rotation (360° rotation). By using spin torque asymmetry to realize an enhanced effective P{sub IPP}, we experimentally demonstrate this behavior in OST devices in parallel to anti-parallel switching. Modeling predicts that decreasing the effective demagnetization field can substantially reduce the minimum C{sub P} required to attain deterministic switching, while retaining low critical switching current, I{sub p}???500??A.

Park, Junbo; Buhrman, R. A. [Cornell University, Ithaca, New York 14853 (United States)] [Cornell University, Ithaca, New York 14853 (United States); Ralph, D. C. [Cornell University, Ithaca, New York 14853 (United States) [Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell, Ithaca, New York 14853 (United States)

2013-12-16T23:59:59.000Z

386

Two ways to perform spin-polarized relativistic linear muffin-tin-orbital calculations  

Science Journals Connector (OSTI)

Two spin-polarized relativistic versions of the linear muffin-tin-orbital method of band-structure calculations are presented. The first one is a pseudoperturbational method taking the effect of spin splitting only into account within the variational step. The second one treats spin polarization and spin-orbit coupling on the same level by making use of the proper solutions to the Dirac equation for a spin-dependent potential. Both approaches permit a detailed theoretical study of magnetocrystalline anisotropy effects. Results for the band structure, the spin and orbital magnetic moments and the conduction-band contribution to the hyperfine fields of Fe, Co, and Ni obtained by these methods are presented and compared to data obtained by an application of the spin-polarized version of the relativistic Korringa-Kohn-Rostoker method.

H. Ebert

1988-11-15T23:59:59.000Z

387

Electronic structures at Magnetic Tunnel Junction interfaces: EELS experiments and FEFF calculations  

Science Journals Connector (OSTI)

Electron transfer between the electrodes in a Magnetic Tunnel Junction (MTJ) is spin-dependent and directly related to the relative orientation of the magnetization of the two ferromagnetic layers on each side...

K. March; D. Imhoff; G. Krill; C. Colliex

2008-01-01T23:59:59.000Z

388

Spin states of para-water and ortho-water molecule in gas and liquid phases  

E-Print Network [OSTI]

Spin degrees of freedom of water molecule in gas and liquid state were investigated in order to provide a reasonable answer about the unsolved problem of a long-term behavior of water spin isomers. The approach used involves an assumption that molecules change their spin state from a pure state to a mixed one when they interact with some sorts of adsorbent surface. Some models and conceptions of the quantum information processing were used.

V. K. Konyukhov

2009-09-23T23:59:59.000Z

389

Electrical detection of 31P spin quantum states  

E-Print Network [OSTI]

In recent years, a variety of solid-state qubits has been realized, including quantum dots, superconducting tunnel junctions and point defects. Due to its potential compatibility with existing microelectronics, the proposal by Kane based on phosphorus donors in Si has also been pursued intensively. A key issue of this concept is the readout of the P quantum state. While electrical measurements of magnetic resonance have been performed on single spins, the statistical nature of these experiments based on random telegraph noise measurements has impeded the readout of single spin states. In this letter, we demonstrate the measurement of the spin state of P donor electrons in silicon and the observation of Rabi flops by purely electric means, accomplished by coherent manipulation of spin-dependent charge carrier recombination between the P donor and paramagnetic localized states at the Si/SiO2 interface via pulsed electrically detected magnetic resonance. The electron spin information is shown to be coupled through the hyperfine interaction with the P nucleus, which demonstrates the feasibility of a recombination-based readout of nuclear spins.

A. R. Stegner; C. Boehme; H. Huebl; M. Stutzmann; K. Lips; M. S. Brandt

2006-07-25T23:59:59.000Z

390

Thermodynamics of the Lévy spin glass  

Science Journals Connector (OSTI)

We investigate the Lévy glass, a mean-field spin-glass model with power-law distributed couplings characterized by a divergent second moment. By combining extensively many small couplings with a spare random backbone of strong bonds the model is intermediate between the Sherrington-Kirkpatrick and the Viana-Bray models. A truncated version where couplings smaller than some threshold ? are neglected can be studied within the cavity method developed for spin glasses on locally treelike random graphs. By performing the limit ??0 in a well-defined way we calculate the thermodynamic functions within replica symmetry and determine the de Almeida-Thouless line in the presence of an external magnetic field. Contrary to previous findings we show that there is no replica-symmetric spin-glass phase. Moreover we determine the leading corrections to the ground-state energy within one-step replica symmetry breaking. The effects due to the breaking of replica symmetry appear to be small in accordance with the intuitive picture that a few strong bonds per spin reduce the degree of frustration in the system.

K. Janzen; A. Engel; M. Mézard

2010-08-30T23:59:59.000Z

391

Positive muon behavior in KCl with and without F centers  

Science Journals Connector (OSTI)

Positive muon behavior in KCl containing F centers has been studied. The muon spin depolarization rate showed a maximum near ... probably due to the fact that free positive muons are trapped by F centers in KCl. ...

Masao Doyama; T. Hatano; Y. Suzuki; R. Nakai; R. Yamamoto…

1984-01-01T23:59:59.000Z

392

Investigation of wettability by NMR microscopy and spin-lattice relaxation  

SciTech Connect (OSTI)

The wettability of reservoir rock has an important impact on the efficiency of oil recovery processes and the distribution of oil and water within the reservoir. One of the potentially useful tools for wettability measurements is nuclear magnetic resonance (NMR) and spin-lattice relaxation. More recently using NMR microscopy NIPER has developed the capability of imaging one- and two-phase fluid systems in reservoir rock at resolutions to 25 microns. Effects seen in the images of fluids within the pore space of rocks near the rock grain surfaces hinted at the possibility of using NMR microscopy to map the wettability variations at grain sites within the pore space. Investigations were begun using NMR microscopy and spin-lattice relaxation time measurements on rock/fluid systems and on well-defined fractional wet model systems to study these effects. Relaxation data has been modelled using the stretched exponential relationship recently introduced. Comparisons of the NMR microscopy results of the model system with the rock results indicate that the observed effects probably do not reflect actual wettability variations within the pore space. The results of the relaxation time measurements reveal that even in the simple model studied, the behavior of two phases is somewhat ambiguous and much more complex and requires more study.

Doughty, D.A.; Tomutsa, Liviu

1993-11-01T23:59:59.000Z

393

Bias voltage dependence of the electron spin depolarization in quantum wires in the quantum Hall regime detected by the resistively detected NMR  

SciTech Connect (OSTI)

We performed the resistively-detected nuclear magnetic resonance (RDNMR) to study the electron spin polarization in the non-equilibrium quantum Hall regime. By measuring the Knight shift, we derive source-drain bias voltage dependence of the electron spin polarization in quantum wires. The electron spin polarization shows minimum value around the threshold voltage of the dynamic nuclear polarization.

Chida, K.; Yamauchi, Y.; Arakawa, T.; Kobayashi, K.; Ono, T. [Institute for Chemical Research, Kyoto University, Kyoto (Japan); Hashisaka, M. [Institute for Chemical Research, Kyoto University, Kyoto, Japan and Department of Physics, Tokyo Institute of Technology, Tokyo (Japan); Nakamura, S. [Institute for Chemical Research, Kyoto University, Kyoto, Japan and AIST, Tsukuba (Japan); Machida, T. [IIS and INQIE, University of Tokyo (Japan)

2013-12-04T23:59:59.000Z

394

Spin-waves in Antiferromagnetically-Coupled Bimetallic Oxalates  

SciTech Connect (OSTI)

Bimetallic oxalates are molecule-based magnets with transition-metal ions M(II) and M (III) arranged on an open honeycomb lattice. Performing a Holstein-Primakoff expansion, we obtain the spin-wave spectrum of antiferromagnetically-coupled bimetallic oxalates as a function of the crystal-field angular momentum L2 and L3 on the M(II) and M (III) sites. Our results are applied to the Fe(II)Mn(III), Ni(II)Mn(III) and V(II)V(III) bimetallic oxalates, where the spin-wave gap varies from 0 meV for quenched angular momentum to as high as 15 meV. The presence or absence of magnetic compensation appears to have no effect on the spin-wave gap.

Reis, Peter L [ORNL; Fishman, Randy Scott [ORNL

2009-01-01T23:59:59.000Z

395

Electron Spin Precession for the Time Fractional Pauli Equation  

E-Print Network [OSTI]

In this work, we aim to extend the application of the fractional calculus in the realm of quantum mechanics. We present a time fractional Pauli equation containing Caputo fractional derivative. By use of the new equation we study the electron spin precession problem in a homogeneous constant magnetic field.

Hosein Nasrolahpour

2011-04-05T23:59:59.000Z

396

NEUTRON SCATTERING EVIDENCE FOR A SPIN-PEIERLS  

E-Print Network [OSTI]

NEUTRON SCATTERING EVIDENCE FOR A SPIN-PEIERLS GROUND STATE IN (TMTTF)2PF6 J.P. POUGET, P. FOURY results · magnetic caracterisation of the samples used · neutron scattering detection of the SP;elastic neutron scattering evidence of SP superlattice reflexions in (TMTTF)2PF6 (H12) Laboratoire Léon

Paris-Sud 11, Université de

397

Spectroscopic Study of (two-dimensional) Molecule-based Magnets: [MII(TCNE)(NCMe)2][SbF6] (M = Fe Mn Ni)  

SciTech Connect (OSTI)

The M-[TCNE] (M = 3d metal; TCNE = tetracyanoethylene) system is one of the most interesting classes of molecule-based magnets, exhibiting a plethora of compositions and structures (inorganic polymer chains, 2D layers, 3D networks, and amorphous solids) with a wide range of magnetic ordering temperatures (up to 400 K). A systematic study of vibrational (both infrared and, for the first time, Raman) properties of the family of new TCNE-based magnets of M{sup II}(TCNE) (NCMe){sub 2}[SbF{sub 6}] [M = Mn, Fe, Ni] composition is discussed in conjunction with their magnetic behavior and newly resolved crystal structures. The vibrational properties of the isolated TCNE{sup {sm_bullet}-} anion in the paramagnetic Bu{sub 4}N [TCNE{sup {sm_bullet}-}] salt and recently characterized 2D layered magnet Fe{sup II}(TCNE)(NCMe){sub 2}[FeCl{sub 4}] are also reported for comparison. Additionally, a linear correlation between {nu}{sub c=c} (a{sub g}) frequency of the TCNE ligand and its formal charge Z (the spin density on the {pi}* orbital), Z = [1571 - {nu}{sub C=C} (ag)]/154.5 [e], is presented. It is shown that monitoring Z by Raman spectroscopy is of great use in providing information that allows understanding the peculiarity of the superexchange interaction in M-[TCNE] magnets and establishing the structure-magnetic properties correlations in this class of magnetic material.

C Olson; C Heth; S Lapidus; P Stephens; G Halder; K Pokhodnya

2011-12-31T23:59:59.000Z

398

Dynamic-angle spinning and double rotation of quadrupolar nuclei  

SciTech Connect (OSTI)

Nuclear magnetic resonance (NMR) spectroscopy of quadrupolar nuclei is complicated by the coupling of the electric quadrupole moment of the nucleus to local variations in the electric field. The quadrupolar interaction is a useful source of information about local molecular structure in solids, but it tends to broaden resonance lines causing crowding and overlap in NMR spectra. Magic- angle spinning, which is routinely used to produce high resolution spectra of spin-{1/2} nuclei like carbon-13 and silicon-29, is incapable of fully narrowing resonances from quadrupolar nuclei when anisotropic second-order quadrupolar interactions are present. Two new sample-spinning techniques are introduced here that completely average the second-order quadrupolar coupling. Narrow resonance lines are obtained and individual resonances from distinct nuclear sites are identified. In dynamic-angle spinning (DAS) a rotor containing a powdered sample is reoriented between discrete angles with respect to high magnetic field. Evolution under anisotropic interactions at the different angles cancels, leaving only the isotropic evolution of the spin system. In the second technique, double rotation (DOR), a small rotor spins within a larger rotor so that the sample traces out a complicated trajectory in space. The relative orientation of the rotors and the orientation of the larger rotor within the magnetic field are selected to average both first- and second-order anisotropic broadening. The theory of quadrupolar interactions, coherent averaging theory, and motional narrowing by sample reorientation are reviewed with emphasis on the chemical shift anisotropy and second-order quadrupolar interactions experienced by half-odd integer spin quadrupolar nuclei. The DAS and DOR techniques are introduced and illustrated with application to common quadrupolar systems such as sodium-23 and oxygen-17 nuclei in solids.

Mueller, K.T. (Lawrence Berkeley Lab., CA (United States) California Univ., Berkeley, CA (United States). Dept. of Chemistry)

1991-07-01T23:59:59.000Z

399

Neutron scattering studies of spin?glass alloys  

Science Journals Connector (OSTI)

Neutron diffraction investigations of binary alloys such as Cu?Mn beginning with the earliest reported measurements in 1957 show no evidence of any long range magnetic order except for the broad short range order peaks at the (1 1/2 0) type positions attributed to both atomic and magnetic short range ordering in alloys containing more than about 10–15 at.% Mn. The current interest in spin glasses is focused on the theoretical possibility of a magnetic phase transition to the spin glass state in the dilute random substitutional alloys. Recently neutron scatteringmeasurements have been attempted to study the dynamics of spins in the alloys with a view to understanding the nature of the processes leading to the spin glass state. Small angle neutron scatteringmeasurements on Au?Fe alloys with Fe concentrations below the percolation threshold for ferromagnetism show a series of q?dependent maxima in the total scattering intensity suggesting a continuum of freezing temperatures. Other measurements employing energy analysis by the time?of?flight technique at somewhat larger q’s on the same and other alloys such as Cu?Mn Pd?Mn show a broad quasi?elastic paramagnetic spectrum at high temperatures whose energy width decreases with decreasing temperature apparently goes through a minimum especially at the higher q’s but always remains finite as T?0 K. The intensity of the quasi?elastic scattering however diminishes progressively below some temperature with a simultaneous continuous increase of the elastic peak intensity. Although the implications of the recent phase transition theories of spin glasses to the dynamics of spins at finite scattering vectors are not entirely clear the present neutron scattering results appear not inconsistent with the alternative picture of a continuous process of freezing of spins occurring at least over a finite temperature range.

A. P. Murani

1978-01-01T23:59:59.000Z

400

MAGNETIC NEUTRON SCATTERING  

SciTech Connect (OSTI)

Much of our understanding of the atomic-scale magnetic structure and the dynamical properties of solids and liquids was gained from neutron-scattering studies. Elastic and inelastic neutron spectroscopy provided physicists with an unprecedented, detailed access to spin structures, magnetic-excitation spectra, soft-modes and critical dynamics at magnetic-phase transitions, which is unrivaled by other experimental techniques. Because the neutron has no electric charge, it is an ideal weakly interacting and highly penetrating probe of matter's inner structure and dynamics. Unlike techniques using photon electric fields or charged particles (e.g., electrons, muons) that significantly modify the local electronic environment, neutron spectroscopy allows determination of a material's intrinsic, unperturbed physical properties. The method is not sensitive to extraneous charges, electric fields, and the imperfection of surface layers. Because the neutron is a highly penetrating and non-destructive probe, neutron spectroscopy can probe the microscopic properties of bulk materials (not just their surface layers) and study samples embedded in complex environments, such as cryostats, magnets, and pressure cells, which are essential for understanding the physical origins of magnetic phenomena. Neutron scattering is arguably the most powerful and versatile experimental tool for studying the microscopic properties of the magnetic materials. The magnitude of the cross-section of the neutron magnetic scattering is similar to the cross-section of nuclear scattering by short-range nuclear forces, and is large enough to provide measurable scattering by the ordered magnetic structures and electron spin fluctuations. In the half-a-century or so that has passed since neutron beams with sufficient intensity for scattering applications became available with the advent of the nuclear reactors, they have became indispensable tools for studying a variety of important areas of modern science, ranging from large-scale structures and dynamics of polymers and biological systems, to electronic properties of today's technological materials. Neutron scattering developed into a vast field, encompassing many different experimental techniques aimed at exploring different aspects of matter's atomic structure and dynamics. Modern magnetic neutron scattering includes several specialized techniques designed for specific studies and/or particular classes of materials. Among these are magnetic reflectometry aimed at investigating surfaces, interfaces, and multilayers, small-angle scattering for the large-scale structures, such as a vortex lattice in a superconductor, and neutron spin-echo spectroscopy for glasses and polymers. Each of these techniques and many others offer exciting opportunities for examining magnetism and warrant extensive reviews, but the aim of this chapter is not to survey how different neutron-scattering methods are used to examine magnetic properties of different materials. Here, we concentrate on reviewing the basics of the magnetic neutron scattering, and on the recent developments in applying one of the oldest methods, the triple axis spectroscopy, that still is among the most extensively used ones. The developments discussed here are new and have not been coherently reviewed. Chapter 2 of this book reviews magnetic small-angle scattering, and modern techniques of neutron magnetic reflectometry are discussed in Chapter 3.

ZALIZNYAK,I.A.; LEE,S.H.

2004-07-30T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

Magnetic neutron scattering (invited)  

Science Journals Connector (OSTI)

The application of neutron scattering techniques to magnetic problems is reviewed. We will first discuss diffraction techniques used to solve magnetic structures as well as to measure magnetic form factors order parameters critical phenomena and the scattering from low?dimensional systems. We will also discuss inelastic scattering techniques including polarized beam methods utilized to determine the spin dynamics of various materials. Information will be provided about the types of spectrometers available at the user?oriented national facilities located at Argonne National Laboratory Brookhaven National Laboratory Los Alamos National Laboratory The National Institute of Standards and Technology and Oak Ridge National Laboratory as well as the spectrometers at the Missouri University Research Reactor.

J. W. Lynn

1994-01-01T23:59:59.000Z

402

Magnetic Order in Kondo-Lattice Systems due to Electron-Electron Interactions  

E-Print Network [OSTI]

source of decoherence of electron spin qubits is the hyperfine coupling of the electron spin the electron spin and lead to the decoherence. This decoherence source can be largely suppressed whenMagnetic Order in Kondo-Lattice Systems due to Electron-Electron Interactions Bernd Braunecker

Braunecker, Bernd

403

Sandia National Laboratories: Spontaneous Coherence and Spin...  

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

Spontaneous Coherence and Spin Texture Spontaneous Coherence and Spin Texture videobanner Spontaneous Coherence and Spin Texture in a Cold Exciton Gas (Watch Video) Speaker:...

404

Ultra-cold methods of atomic hydrogen electron spin separation  

SciTech Connect (OSTI)

Two ultra-cold methods of atomic hydrogen electron spin separation for polarized jet targets and sources will be described and compared. Both of them use a helium-film coated cell at 300 mK located in a high magnetic field. The first one, microwave driven extraction, uses a 212 GHz microwave system and 7.5 T magnetic field with a high uniformity ({Delta}B/B{approx} 10{sup {minus}5}). The second method employs the gradient of a high magnetic field for the state separation and beam formation. Experimental results from the two methods will be presented.

Luppov, V.G.; Kaufman, W.A.; Krisch, A.D. [Univ. of Michigan, Ann Arbor, MI (United States)] [and others

1995-04-01T23:59:59.000Z

405

Polarization analysis of neutron reflectometry on non-collinear magnetic media: polarized neutron reflectometry experiments on a thin cobalt film  

Science Journals Connector (OSTI)

In this work we present a full data analysis of polarized neutron reflectometry experiments on a thin magnetic film. A magnetic field was applied perpendicular to the layer magnetization, resulting in non spin-flip and spin-flip reflectivities. For moderate external fields, the gain or loss of Zeeman energy for spin-flipped neutrons results in off-specular reflected spin-flipped beams. The theoretical model used to explain all data simultaneously consists of a bulk cobalt layer, together with interfacial layers with low magnetization values.

R.W.E van de Kruijs; H Fredrikze; M.Th Rekveldt; A.A van Well; Yu.V Nikitenko; V.G Syromyatnikov

2000-01-01T23:59:59.000Z

406

Magnetic edge states in Aharonov-Bohm graphene quantum rings  

SciTech Connect (OSTI)

The effect of electron-electron interaction on the electronic structure of Aharonov-Bohm (AB) graphene quantum rings (GQRs) is explored theoretically using the single-band tight-binding Hamiltonian and the mean-field Hubbard model. The electronic states and magnetic properties of hexagonal, triangular, and circular GQRs with different sizes and zigzag edge terminations are studied. The results show that, although the AB oscillations in the all types of nanoring are affected by the interaction, the spin splitting in the AB oscillations strongly depends on the geometry and the size of graphene nanorings. We found that the total spin of hexagonal and circular rings is zero and therefore, no spin splitting can be observed in the AB oscillations. However, the non-zero magnetization of the triangular rings breaks the degeneracy between spin-up and spin-down electrons, which produces spin-polarized AB oscillations.

Farghadan, R., E-mail: rfarghadan@kashanu.ac.ir; Heidari Semiromi, E. [Department of Physics, University of Kashan, Kashan (Iran, Islamic Republic of); Saffarzadeh, A. [Department of Physics, Payame Noor University, P.O. Box 19395-3697 Tehran (Iran, Islamic Republic of); Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada)

2013-12-07T23:59:59.000Z

407

Zero-Field Splitting in Pseudotetrahedral Co(II) Complexes: a Magnetic, High-Frequency and -Field EPR, and Computational Study  

Science Journals Connector (OSTI)

(4) In this case the correlation is represented by a straight line (in fact by two, nearly collinear, straight lines) for a geometry of compressed/elongated tetragonal bipyramid keeping D4h symmetry. ... magnet behavior in the absence of an applied magnetic field. ... ESR technique in magnetic fields ?17 T. A field-induced development of the soliton-like incommensurate superstructure is clearly indicated as a pronounced increase of the magnon spin resonance linewidth ?B, with a ?Bmax at Bc ? 13.8 T. The anomaly is explained in terms of the magnon-soliton scattering and suggests that the soliton-like phase exists close to the boundary of the dimerized-incommensurate phase transition. ...

Monika Idešicová; Ján Titiš; J. Krzystek; Roman Bo?a

2013-08-07T23:59:59.000Z

408

Maximal spin and energy conversion efficiency in a symbiotic system of black hole, disk and jet  

E-Print Network [OSTI]

We study a combined model of black hole - accretion disk - magnetosphere - jet symbiosis, applicable for supermassive black holes. We quantify the mass and spin evolution and we analyze how the limiting value of the spin parameter and the conversion efficiency of accreted mass into radiation depend on the interplay of electromagnetic radiation reaction, magnetosphere characteristics and truncation radius of radiation. The dominant effect comes from the closed magnetic field line region, which reduces the spin limit to values ~0.89 (instead ~0.99 in its absence). Therefore observations on black hole spins could favour or disfavour the existence of the closed magnetic field line region (or its coupling to the disk). We also find that the suppression of radiation from the innermost part of the accretion disk, inferred from observations, and a collimated jet both increase the spin limit and the energy conversion efficiency.

Zoltán Kovács; László Á. Gergely; Peter L. Biermann

2010-07-24T23:59:59.000Z

409

A planar ion trap chip with integrated structures for an adjustable magnetic field gradient  

E-Print Network [OSTI]

field necessary for magnetic-gradient- induced coupling between ionic effective spins. We dem- onstrate] magnetic field gradient, however, such coupling is induced. Also, coupling between spin states of different-gradient- induced coupling (MAGIC). A static gradient can be generated by permanent mag- nets [15, 16] or by current

Wunderlich, Christof

410

Decoherence from spin environments  

Science Journals Connector (OSTI)

We examine two exactly solvable models of decoherence—a central spin-system, (i) with and (ii) without a self-Hamiltonian, interacting with a collection of environment spins. In the absence of a self-Hamiltonian we show that in this model (introduced some time ago to illustrate environment-induced superselection) generic assumptions about the coupling strengths can lead to a universal (Gaussian) suppression of coherence between pointer states. On the other hand, we show that when the dynamics of the central spin is dominant a different regime emerges, which is characterized by a non-Gaussian decay and a dramatically different set of pointer states. We explore the regimes of validity of the Gaussian decay and discuss its relation to the spectral features of the environment and to the Loschmidt echo (or fidelity).

F. M. Cucchietti; J. P. Paz; W. H. Zurek

2005-11-29T23:59:59.000Z

411

Neutron diffraction and specific heat studies on the magnetic ordering in the [Fe{sup II}({delta})Fe{sup II}({lambda})(ox){sub 2}(Phen){sub 2}]{sub n} molecular magnet  

SciTech Connect (OSTI)

The magnetic characteristics of the molecular magnet [Fe{sup II}({delta})Fe{sup II}({lambda})(ox){sub 2}(Phen){sub 2}]{sub n}, having chemical formula C{sub 28}H{sub 16}Fe{sub 2}N{sub 4}O{sub 8} for unity, has been studied by magnetization, neutron diffraction, and field-dependent specific heat-measurements. In the high-temperature regime (T>T{sub m}), the one-dimensional Ising chain model with alternate Lande factors is applied to describe its quasiferrimagnetic behavior as temperature approaches T{sub m}. In the low-temperature region (Tmagnetic ordering as indicated by an anomaly in specific heat. Furthermore, an intrinsic antiparallel alignment of spins with a net ferrimagnetic structure is deduced from neutron diffraction study. The field-dependent {lambda}-type anomaly of specific heat indicates that applying a magnetic field raises magnetic ordering temperature. An additional small anomaly in specific heat is also seen below T{sub m}, which could be due to the zero-field splitting caused by the internal crystal field.

Ho, C. J.; Her, J. L.; Sun, C. P.; Huang, C. L.; Chou, C. C.; Yang, H. D. [Department of Physics, Center of Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Yang, C. C.; Li, W. H. [Department of Physics and Center for Neutron Beam Applications, National Central University, Chung-Li 32054, Taiwan (China); Li Lulin; Lin, K. J. [Department of Chemistry, Center of Nanoscience and Nanotechnology, National Chung-Hsing University, Taichung 402, Taiwan (China); Lynn, J. W. [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

2007-12-01T23:59:59.000Z

412

Spin-Charge Separation in the Quantum Spin Hall State  

Science Journals Connector (OSTI)

The quantum spin Hall state is a topologically nontrivial insulator state protected by the time-reversal symmetry. We show that such a state always leads to spin-charge separation in the presence of a ? flux. Our result is generally valid for any interacting system. We present a proposal to experimentally observe the phenomenon of spin-charge separation in the recently discovered quantum spin Hall system.

Xiao-Liang Qi and Shou-Cheng Zhang

2008-08-19T23:59:59.000Z

413

Magnetic structure and spin reorientation in the ternary sulfides, Ni{sub x}Cr{sub 3-x}S{sub 4} (x = 1/4, 1/2, 3/4)  

SciTech Connect (OSTI)

Powder neutron diffraction data for Ni{sub x}Cr{sub 3-x}S{sub 4} (x = {1/4}, {1/2}, 3/4) collected over the temperature range 1.8 {le} T {le} 286 K demonstrate that all phases exhibit long-range magnetic order at low temperatures. The magnetic ordering temperature is composition dependent and increases with decreasing nickel content (205, 210, and 218 K for x = 3/4, {1/2}, and {1/4}, respectively). The magnetic structure determined at 1.8 K involves a doubling of the unit cell in both the a and the c directions. Moments associated with cations in a fully occupied metal layer, directed parallel to the cation layers, show little compositional dependence, whereas those associated with cations in an ordered vacancy layer are directed toward the anion layers and have a maximum value at the composition corresponding to x = {1/2}. At temperatures between 1.8 K and the ordering temperature, materials with compositions corresponding to x = {1/4} and 3/4 show a gradual 90{degree} reorientation of the direction of the vacancy layer moments such that at temperatures just below the ordering temperature, moments lie parallel to the crystallographic b-axis.

Powell, A.V.; Colgan, D.C. [Heriot-Watt Univ., Edinburgh (United Kingdom). Dept. of Chemistry] [Heriot-Watt Univ., Edinburgh (United Kingdom). Dept. of Chemistry; Ritter, C. [Inst. Max von Laue-Paul Langevin, Grenoble (France)] [Inst. Max von Laue-Paul Langevin, Grenoble (France)

1999-03-01T23:59:59.000Z

414

Lensless Imaging of Magnetic Nanostructures  

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

Lensless Imaging of Magnetic Lensless Imaging of Magnetic Nanostructures Lensless Imaging of Magnetic Nanostructures Print Wednesday, 28 March 2012 00:00 Magnetism is useful for many devices and techniques, from electric motors and computer hard drives to magnetic resonance imaging used in medicine. By studying the basics of magnetism, scientists aim to better understand the fundamental physical principles that govern magnetic systems, perhaps leading to important new technologies. The high brightness and coherence of the ALS's soft x-rays have enabled scientists to apply lensless x-ray imaging for the first time to nanometer-scale magnetic structures in an alloy. Many Ways To See You open your eyes and detect the light rays streaming through your bedroom window (transmission), illuminating your socks on the floor (scattering). You put on your glasses (refraction) to detect the state of your image in the mirror (reflection). If you are an ALS scientist, perhaps you go to work and shine some x-ray light on a crystal to detect the arrangement of the atoms in the crystal (diffraction). Now, thanks to Turner et al., you can also shine some x-ray light on a magnetic sample to detect the arrangement of its electron spins through a method known as lensless imaging. This last example is an equally valid way to "see," but instead of using windows, lenses, or mirrors to manipulate light and construct an image, mathematical formulas are used to describe the effects that particles and fields in the sample have on the light. These formulas have always contained terms that relate to the electron spin of magnetic atoms, but they were previously ignored. Using the full formula allows for the determination of not only crystal structure, but magnetic spin distribution and orientation as well, with a spatial resolution limited only by the wavelength of x-rays used. This promising method can be used at any coherent light source, including modern x-ray free-electron lasers, where ultrashort pulses would freeze-frame magnetic changes, offering the potential for imaging in unprecedented detail the structure and motion of boundaries between regions with different magnetic orientation.

415

Quantum spin dynamics  

E-Print Network [OSTI]

The classical Landau-Lifshitz equation has been derived from quantum mechanics. Starting point is the assumption of a non-Hermitian Hamilton operator to take the energy dissipation into account. The corresponding quantum mechanical time dependent Schr\\"odinger, Liouville and Heisenberg equation have been described and the similarities and differences between classical and quantum mechanical spin dynamics have been discussed. Furthermore, a time dependent Schr\\"odinger equation corresponding to the classical Landau-Lifshitz-Gilbert equation and two ways to include temperature into the quantum mechanical spin dynamics have been proposed.

Robert Wieser

2014-10-23T23:59:59.000Z

416

RHIC Spin Program Goals of RHIC Spin Program  

E-Print Network [OSTI]

longitudinal polarization · polarized atomic hydrogen jet target Installed and commissioned during run 4 violating production of W± · Transverse spin: Transversity () & transverse spin effects with connections to orbital angular momentum (Ly) #12;5/11/2006 L.C.Bland, DOE Review of MEP 5 Methods to Address Spin

417

X-Ray Diffraction Microscopy of Magnetic Structures  

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

X-Ray Diffraction Microscopy of Magnetic Structures Print X-Ray Diffraction Microscopy of Magnetic Structures Print science brief icon Scientists working at ALS Beamline 12.0.2.2 have demonstrated a new x-ray technique for producing short-exposure nanoscale images of the magnetic structure of materials. The new method combines aspects of coherent x-ray diffraction, which can determine 3-D charge distributions, and resonant magnetic scattering, which is sensitive to magnetic structures. Physicists have used coherent x-ray diffraction to measure the electron density of complicated molecules. The formula used to make these calculations contains terms that relate to the electron spin of magnetic atoms, but these terms are traditionally ignored since coherent x-ray diffraction has not been used to retrieve magnetic information. Using the full formula allows for the determination of not only the electron density, but also the magnetic spin distribution and its orientation.

418

X-Ray Diffraction Microscopy of Magnetic Structures  

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

X-Ray Diffraction Microscopy of Magnetic Structures Print X-Ray Diffraction Microscopy of Magnetic Structures Print science brief icon Scientists working at ALS Beamline 12.0.2.2 have demonstrated a new x-ray technique for producing short-exposure nanoscale images of the magnetic structure of materials. The new method combines aspects of coherent x-ray diffraction, which can determine 3-D charge distributions, and resonant magnetic scattering, which is sensitive to magnetic structures. Physicists have used coherent x-ray diffraction to measure the electron density of complicated molecules. The formula used to make these calculations contains terms that relate to the electron spin of magnetic atoms, but these terms are traditionally ignored since coherent x-ray diffraction has not been used to retrieve magnetic information. Using the full formula allows for the determination of not only the electron density, but also the magnetic spin distribution and its orientation.

419

X-Ray Diffraction Microscopy of Magnetic Structures  

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

X-Ray Diffraction Microscopy of Magnetic Structures Print X-Ray Diffraction Microscopy of Magnetic Structures Print science brief icon Scientists working at ALS Beamline 12.0.2.2 have demonstrated a new x-ray technique for producing short-exposure nanoscale images of the magnetic structure of materials. The new method combines aspects of coherent x-ray diffraction, which can determine 3-D charge distributions, and resonant magnetic scattering, which is sensitive to magnetic structures. Physicists have used coherent x-ray diffraction to measure the electron density of complicated molecules. The formula used to make these calculations contains terms that relate to the electron spin of magnetic atoms, but these terms are traditionally ignored since coherent x-ray diffraction has not been used to retrieve magnetic information. Using the full formula allows for the determination of not only the electron density, but also the magnetic spin distribution and its orientation.

420

Magnetism in Iron at High Temperatures  

Science Journals Connector (OSTI)

Magnetism in iron at high temperature is investigated by calculating the total electronic band-structure energy for four types of spin arrangements. A slow smooth spatial variation of spin direction costs relatively little energy and the atomic moment m is reduced only ? 10%. More rapid variations have considerably higher energy, which may explain the high degree of short-range order and small ?m observed at T?TC. Other aspects are also discussed.

M. V. You; V. Heine; A. J. Holden; P. J. Lin-Chung

1980-05-12T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

Magnetic Spinner  

Science Journals Connector (OSTI)

A science toy sometimes called the “magnetic spinner” is an interesting class demonstration to illustrate the principles of magnetic levitation. It can also be used to demonstrate Faraday's law and a horizontally suspended physical pendulum. The levitated part contains two circular magnets encased in a plastic housing. Each magnet stays above two triangular magnets fixed to the base. The magnetic repulsive force experienced by the circular magnets is independent of their orientation; therefore the holder of these magnets can be rotated without affecting its stability. The holder with the circular magnets can be oscillated up and down as a horizontally suspended physical pendulum.

P. J. Ouseph

2006-01-01T23:59:59.000Z

422

Transverse Spin Physics: Recent Developments  

SciTech Connect (OSTI)

Transverse-spin physics has been very active and rapidly developing in the last few years. In this talk, I will briefly summarize recent theoretical developments, focusing on the associated QCD dynamics in transverse spin physics.

Yuan, Feng

2008-12-10T23:59:59.000Z

423

Dynamics, crystallization and structures in colloid spin coating  

E-Print Network [OSTI]

Spin coating is an out-of-equilibrium technique for producing polymer films and colloidal crystals quickly and reproducibly. In this review, we present an overview of theoretical and experimental studies of the spin coating of colloidal suspensions. The dynamics of the spin coating process is discussed first, and we present insights from both theory and experiment. A key difference between spin coating with polymer solutions and with monodisperse colloidal suspensions is the emergence of long range (centimeter scale) orientational correlations in the latter. We discuss experiments in different physical regimes that shed light on the many unusual partially-ordered structures that have long-range orientational order, but no long-range translational order. The nature of these structures can be tailored by adding electric or magnetic fields during the spin coating procedure. These partially-ordered structures can be considered as model systems for studying the fundamentals of poorly crystalline and defect-rich solids, and they can also serve as templates for patterned and/or porous optical and magnetic materials.

Moorthi Pichumani; Payam Bagheri; Kristin M. Poduska; Wenceslao Gonzalez-Vinas; Anand Yethiraj

2013-01-10T23:59:59.000Z

424

Magnetism Digest  

Science Journals Connector (OSTI)

... and Institute of Electrical and Electronic Engineers, on the occasion of their annual conferences on magnetism and magnetic materials in the United States, have sponsored the production of a Magnetic ... references, drawn from a large number of sources, to work in the field of magnetism and magnetic materials published in the preceding year. They therefore provide a very convenient ...

J. H. PHILLIPS

1966-06-25T23:59:59.000Z

425

Magnetic Moment of the Free Muon  

Science Journals Connector (OSTI)

The magnetic moment of the positive ? meson has been measured in several target materials by a magnetic resonance technique. Muons were brought to rest with their spins parallel to a magnetic field. A radio-frequency pulse was applied to effect a spin reorientation which was detected by counting the decay electrons emerging after the pulse in a fixed direction. Results are expressed in terms of a g factor which for a spin 1/2 particle is the ratio of the actual moment to e?2m?c. The most accurate result obtained in a CHBr3 target, is that g=2(1.0026±0.0009) compared to the theoretical prediction of g=2(1.0012). Less accurate measurements yielded g=2.005±0.005 in a copper target and g=2.00±0.01 in a lead target.

T. Coffin; R. L. Garwin; S. Penman; L. M. Lederman; A. M. Sachs

1958-02-01T23:59:59.000Z

426

Role of cooperative lattice distortion in the charge, orbital, and spin ordering in doped manganites  

Science Journals Connector (OSTI)

The role of lattice distortion in the charge, orbital, and spin ordering in half-doped manganites has been investigated. For fixed magnetic ordering, we show that the cooperative lattice distortion stabilize the experimentally observed ordering even when the strong onsite electronic correlation is taken into account. Furthermore, without invoking the magnetic interactions, the cooperative lattice distortion alone may lead to the correct charge and orbital ordering including the charge stacking effect, and the magnetic ordering can be the consequence of such a charge and orbital ordering. We propose that the cooperative nature of the lattice distortion is essential to understand the complicated charge, orbital, and spin ordering observed in doped manganites.

R. Y. Gu and C. S. Ting

2002-06-07T23:59:59.000Z

427

Many-body Interactions in Magnetic Films and Nanostructures  

SciTech Connect (OSTI)

We describe results supported by DOE grant DE-FG02-04ER46158, which focused on magnetic interaction at surfaces, in thin films, and in metallic nanostructures. We report on three general topics: 1) The Rashba spin splitting at magnetic surfaces of rare earth metals, 2) magnetic nanowires self-assembled on stepped tungsten single crystals, and 3) magnetic interaction in graphene films doped with hydrogen atoms.

Stephen D. Kevan

2012-12-12T23:59:59.000Z

428

ACCELERATION INDUCED SPIN AND  

E-Print Network [OSTI]

spin at each event. A unique and natural law of parallel transport of quantum states between different mechanical line of reasoning leads to the heuristic con* *clusion that gravitation is to be identified AND ITS GAUGE GEOMETRY The line of reasoning which lies at the base of Einstein's gravitation the

Gerlach, Ulrich

429

Muon spin rotation  

Science Journals Connector (OSTI)

... vast funding accorded high energy physics research in recent years.?SR-the acronym stands for Muon Spin Rotation, Relaxation, Resonance, Research or what have you, and refers to the ... the most promising new work related to purely chemical problems. Indeed, the use of muons in chemistry is striking not only for providing yet another probe of chemical systems, ...

G. C. Stirling

1978-11-23T23:59:59.000Z

430

Rotational Doppler effect in magnetic resonance  

Science Journals Connector (OSTI)

We compute the shift in the frequency of the spin resonance in a solid that rotates in the field of a circularly polarized electromagnetic wave. Electron-spin resonance, nuclear magnetic resonance, and ferromagnetic resonance are considered. We show that contrary to the case of the rotating LC circuit, the shift in the frequency of the spin resonance has strong dependence on the symmetry of the receiver. The shift due to rotation occurs only when rotational symmetry is broken by the anisotropy of the gyromagnetic tensor, by the shape of the body or by magnetocrystalline anisotropy. General expressions for the resonance frequency and power absorption are derived and implications for experiment are discussed.

S. Lendínez; E. M. Chudnovsky; J. Tejada

2010-11-12T23:59:59.000Z

431

Multiple magnetic barriers in graphene  

Science Journals Connector (OSTI)

We study the behavior of charge carriers in graphene in inhomogeneous perpendicular magnetic fields. We consider two types of one-dimensional magnetic profiles, uniform in one direction: a sequence of N magnetic barriers and a sequence of alternating magnetic barriers and wells. In both cases, we compute the transmission coefficient of the magnetic structure by means of the transfer-matrix formalism and the associated conductance. In the first case the structure becomes increasingly transparent upon increasing N at fixed total magnetic flux. In the second case we find strong wave-vector filtering and resonant effects. We also calculate the band structure of a periodic magnetic superlattice and find a wave-vector-dependent gap around zero energy.

Luca Dell’Anna and Alessandro De Martino

2009-01-26T23:59:59.000Z

432

Computer Simulation of Quantum Dynamics in a Classical Spin Environment  

E-Print Network [OSTI]

In this paper a formalism for studying the dynamics of quantum systems coupled to classical spin environments is reviewed. The theory is based on generalized antisymmetric brackets and naturally predicts open-path off-diagonal geometric phases in the evolution of the density matrix. It is shown that such geometric phases must also be considered in the quantum-classical Liouville equation for a classical bath with canonical phase space coordinates; this occurs whenever the adiabatics basis is complex (as in the case of a magnetic field coupled to the quantum subsystem). When the quantum subsystem is weakly coupled to the spin environment, non-adiabatic transitions can be neglected and one can construct an effective non-Markovian computer simulation scheme for open quantum system dynamics in classical spin environments. In order to tackle this case, integration algorithms based on the symmetric Trotter factorization of the classical-like spin propagator are derived. Such algorithms are applied to a model comprising a quantum two-level system coupled to a single classical spin in an external magnetic field. Starting from an excited state, the population difference and the coherences of this two-state model are simulated in time while the dynamics of the classical spin is monitored in detail. It is the author's opinion that the numerical evidence provided in this paper is a first step toward developing the simulation of quantum dynamics in classical spin environments into an effective tool. In turn, the ability to simulate such a dynamics can have a positive impact on various fields, among which, for example, nano-science.

Alessandro Sergi

2014-04-24T23:59:59.000Z

433

Lensless Imaging of Magnetic Nanostructures  

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

Lensless Imaging of Magnetic Nanostructures Print Lensless Imaging of Magnetic Nanostructures Print Magnetism is useful for many devices and techniques, from electric motors and computer hard drives to magnetic resonance imaging used in medicine. By studying the basics of magnetism, scientists aim to better understand the fundamental physical principles that govern magnetic systems, perhaps leading to important new technologies. The high brightness and coherence of the ALS's soft x-rays have enabled scientists to apply lensless x-ray imaging for the first time to nanometer-scale magnetic structures in an alloy. Many Ways To See You open your eyes and detect the light rays streaming through your bedroom window (transmission), illuminating your socks on the floor (scattering). You put on your glasses (refraction) to detect the state of your image in the mirror (reflection). If you are an ALS scientist, perhaps you go to work and shine some x-ray light on a crystal to detect the arrangement of the atoms in the crystal (diffraction). Now, thanks to Turner et al., you can also shine some x-ray light on a magnetic sample to detect the arrangement of its electron spins through a method known as lensless imaging. This last example is an equally valid way to "see," but instead of using windows, lenses, or mirrors to manipulate light and construct an image, mathematical formulas are used to describe the effects that particles and fields in the sample have on the light. These formulas have always contained terms that relate to the electron spin of magnetic atoms, but they were previously ignored. Using the full formula allows for the determination of not only crystal structure, but magnetic spin distribution and orientation as well, with a spatial resolution limited only by the wavelength of x-rays used. This promising method can be used at any coherent light source, including modern x-ray free-electron lasers, where ultrashort pulses would freeze-frame magnetic changes, offering the potential for imaging in unprecedented detail the structure and motion of boundaries between regions with different magnetic orientation.

434

Lensless Imaging of Magnetic Nanostructures  

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

Lensless Imaging of Magnetic Nanostructures Print Lensless Imaging of Magnetic Nanostructures Print Magnetism is useful for many devices and techniques, from electric motors and computer hard drives to magnetic resonance imaging used in medicine. By studying the basics of magnetism, scientists aim to better understand the fundamental physical principles that govern magnetic systems, perhaps leading to important new technologies. The high brightness and coherence of the ALS's soft x-rays have enabled scientists to apply lensless x-ray imaging for the first time to nanometer-scale magnetic structures in an alloy. Many Ways To See You open your eyes and detect the light rays streaming through your bedroom window (transmission), illuminating your socks on the floor (scattering). You put on your glasses (refraction) to detect the state of your image in the mirror (reflection). If you are an ALS scientist, perhaps you go to work and shine some x-ray light on a crystal to detect the arrangement of the atoms in the crystal (diffraction). Now, thanks to Turner et al., you can also shine some x-ray light on a magnetic sample to detect the arrangement of its electron spins through a method known as lensless imaging. This last example is an equally valid way to "see," but instead of using windows, lenses, or mirrors to manipulate light and construct an image, mathematical formulas are used to describe the effects that particles and fields in the sample have on the light. These formulas have always contained terms that relate to the electron spin of magnetic atoms, but they were previously ignored. Using the full formula allows for the determination of not only crystal structure, but magnetic spin distribution and orientation as well, with a spatial resolution limited only by the wavelength of x-rays used. This promising method can be used at any coherent light source, including modern x-ray free-electron lasers, where ultrashort pulses would freeze-frame magnetic changes, offering the potential for imaging in unprecedented detail the structure and motion of boundaries between regions with different magnetic orientation.

435

Lensless Imaging of Magnetic Nanostructures  

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

Lensless Imaging of Magnetic Nanostructures Print Lensless Imaging of Magnetic Nanostructures Print Magnetism is useful for many devices and techniques, from electric motors and computer hard drives to magnetic resonance imaging used in medicine. By studying the basics of magnetism, scientists aim to better understand the fundamental physical principles that govern magnetic systems, perhaps leading to important new technologies. The high brightness and coherence of the ALS's soft x-rays have enabled scientists to apply lensless x-ray imaging for the first time to nanometer-scale magnetic structures in an alloy. Many Ways To See You open your eyes and detect the light rays streaming through your bedroom window (transmission), illuminating your socks on the floor (scattering). You put on your glasses (refraction) to detect the state of your image in the mirror (reflection). If you are an ALS scientist, perhaps you go to work and shine some x-ray light on a crystal to detect the arrangement of the atoms in the crystal (diffraction). Now, thanks to Turner et al., you can also shine some x-ray light on a magnetic sample to detect the arrangement of its electron spins through a method known as lensless imaging. This last example is an equally valid way to "see," but instead of using windows, lenses, or mirrors to manipulate light and construct an image, mathematical formulas are used to describe the effects that particles and fields in the sample have on the light. These formulas have always contained terms that relate to the electron spin of magnetic atoms, but they were previously ignored. Using the full formula allows for the determination of not only crystal structure, but magnetic spin distribution and orientation as well, with a spatial resolution limited only by the wavelength of x-rays used. This promising method can be used at any coherent light source, including modern x-ray free-electron lasers, where ultrashort pulses would freeze-frame magnetic changes, offering the potential for imaging in unprecedented detail the structure and motion of boundaries between regions with different magnetic orientation.

436

Lensless Imaging of Magnetic Nanostructures  

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

Lensless Imaging of Magnetic Nanostructures Print Lensless Imaging of Magnetic Nanostructures Print Magnetism is useful for many devices and techniques, from electric motors and computer hard drives to magnetic resonance imaging used in medicine. By studying the basics of magnetism, scientists aim to better understand the fundamental physical principles that govern magnetic systems, perhaps leading to important new technologies. The high brightness and coherence of the ALS's soft x-rays have enabled scientists to apply lensless x-ray imaging for the first time to nanometer-scale magnetic structures in an alloy. Many Ways To See You open your eyes and detect the light rays streaming through your bedroom window (transmission), illuminating your socks on the floor (scattering). You put on your glasses (refraction) to detect the state of your image in the mirror (reflection). If you are an ALS scientist, perhaps you go to work and shine some x-ray light on a crystal to detect the arrangement of the atoms in the crystal (diffraction). Now, thanks to Turner et al., you can also shine some x-ray light on a magnetic sample to detect the arrangement of its electron spins through a method known as lensless imaging. This last example is an equally valid way to "see," but instead of using windows, lenses, or mirrors to manipulate light and construct an image, mathematical formulas are used to describe the effects that particles and fields in the sample have on the light. These formulas have always contained terms that relate to the electron spin of magnetic atoms, but they were previously ignored. Using the full formula allows for the determination of not only crystal structure, but magnetic spin distribution and orientation as well, with a spatial resolution limited only by the wavelength of x-rays used. This promising method can be used at any coherent light source, including modern x-ray free-electron lasers, where ultrashort pulses would freeze-frame magnetic changes, offering the potential for imaging in unprecedented detail the structure and motion of boundaries between regions with different magnetic orientation.

437

Magnetic K-edge absorption in 3d elements and its relation to local magnetic structure  

Science Journals Connector (OSTI)

In this paper we present a selection of circular magnetic x-ray dichroism (CMXD) measurements at the K edges of Fe, Ni, Co, and Mn in various alloys and compounds. We investigate the correlation between the measured spin-dependent absorption signal and the p-like spin polarization of the unoccupied bands at the Fermi level. In the case of Fe we find a direct correlation of the spin-dependent absorption profile to the p-like spin polarizations. This is discussed for various alloys. The measured CMXD signals are compared with theoretical calculations for the absorption spectra. For Fe and Ni we have performed spin-polarized relativistic Korringa-Kohn-Rostoker Green’s function calculations, which give a parameter-free description of the spin-dependent absorption process. The content of information in the experimental CMXD spectra on the local magnetic p and d moments is discussed in comparison with the calculated changes of the p and d moments. In the case of the Co and Ni K edges we find a direct correlation of the average strength of the spin-dependent absorption signal to the p moment. For Co also a direct correlation to the d moment is indicated. At Fe K edges no proportionality of any features of the spin-dependent absorption profile to p or d moments have been found.

S. Stähler, G. Schütz, and H. Ebert

1993-01-01T23:59:59.000Z

438

Three fluid hydrodynamics of spin-1 Bose-Einstein condensates  

E-Print Network [OSTI]

We study excitations of the spin-1 Bose gas at finite temperatures and in the presence of a not so strong magnetic field, or equivalently, when the gas sample is partially polarized. Motivated by the success of two-fluid hydrodynamics of scalar superfluids we develop a three-fluid hydrodynamic description to treat the low frequency and long wavelength excitations of the spin-1 Bose gas. We derive the coupled linear hydrodynamic equations of the three sounds and evaluate them numerically in a self-consistent mean field approximation valid for the dilute gas at the intermediate and critical temperature regions. In this latter region we identify the critical mode.

Gergely Szirmai; Peter Szepfalusy

2011-12-14T23:59:59.000Z

439

Three fluid hydrodynamics of spin-1 Bose-Einstein condensates  

E-Print Network [OSTI]

We study excitations of the spin-1 Bose gas at finite temperatures and in the presence of a not so strong magnetic field, or equivalently, when the gas sample is partially polarized. Motivated by the success of two-fluid hydrodynamics of scalar superfluids we develop a three-fluid hydrodynamic description to treat the low frequency and long wavelength excitations of the spin-1 Bose gas. We derive the coupled linear hydrodynamic equations of the three sounds and evaluate them numerically in a self-consistent mean field approximation valid for the dilute gas at the intermediate and critical temperature regions. In this latter region we identify the critical mode.

Szirmai, Gergely

2011-01-01T23:59:59.000Z

440

Deep spin-glass hysteresis-area collapse and scaling in the three-dimensional ±J Ising model  

E-Print Network [OSTI]

We investigate the dissipative loss in the ±J Ising spin glass in three dimensions through the scaling of the hysteresis area, for a maximum magnetic field that is equal to the saturation field. We perform a systematic ...

Sariyer, Ozan S.

Note: This page contains sample records for the topic "magnetic spin behavior" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
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441

Nonlinear magnetization of graphene  

Science Journals Connector (OSTI)

We compute the magnetization of graphene in a magnetic field, taking into account for generality the possibility of a mass gap. We concentrate on the physical regime where quantum oscillations are not observed due to the effect of the temperature or disorder and show that the magnetization exhibits nonlinear behavior as a func