Sample records for magnetic spin behavior

  1. MAGNETIC BEHAVIOR OF ATOMICALLY ENGINEERED NiOCoCu-BASED GIANT MAGNETORESISTANCE SPIN

    E-Print Network [OSTI]

    Chopra, Harsh Deep

    generation of read-heads for high-density data storage devices using GMR multilayers [6]. A broad category symmetric spin valves are discussed in relation to the modi®cation of interfaces and nanostructure using- dition to a fundamental interest in the physics of thin ®lm magnetism, these systems have device ap

  2. Magnetic and dielectric behavior of the spin-chain compound Er{sub 2}BaNiO{sub 5} well below its Néel temperature

    SciTech Connect (OSTI)

    Basu, Tathamay; Singh, Kiran; Sampathkumaran, E. V. [Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005 (India); Mohapatra, N. [School of Basic Sciences, Indian Institute of Technology Bhubaneshwar, Bhubaneshwar 751013 (India)

    2014-09-21T23:59:59.000Z

    We have recently reported that the Haldane spin-chain system, Er{sub 2}BaNiO{sub 5}, undergoing antiferromagnetic order below (T{sub N}=) 32?K, is characterized by the onset of ferroelectricity near 60?K due to magnetoelectric coupling induced by short-range magnetic-order within spin-chains. We have carried out additional magnetic and dielectric studies to understand the properties well below T{sub N}. We emphasize here on the following: (i) A strong frequency dependent behaviors of ac magnetic susceptibility and complex dielectric properties have been observed at much lower temperatures (<8?K), that is, “reentrant multiglass-like” phenomenon, naturally suggesting the existence of an additional transition well below T{sub N}. (ii) “Magnetoelectric phase coexistence” is observed at very low temperature (e.g., T?=?2?K), where the high-field magnetoelectric phase is partially arrested on returning to zero magnetic field after a cycling through metamagnetic transition.

  3. Magnetic Monopoles in Spin Ice

    E-Print Network [OSTI]

    Claudio Castelnovo; Roderich Moessner; Shivaji L. Sondhi

    2007-10-31T23:59:59.000Z

    Electrically charged particles, such as the electron, are ubiquitous. By contrast, no elementary particles with a net magnetic charge have ever been observed, despite intensive and prolonged searches. We pursue an alternative strategy, namely that of realising them not as elementary but rather as emergent particles, i.e., as manifestations of the correlations present in a strongly interacting many-body system. The most prominent examples of emergent quasiparticles are the ones with fractional electric charge e/3 in quantum Hall physics. Here we show that magnetic monopoles do emerge in a class of exotic magnets known collectively as spin ice: the dipole moment of the underlying electronic degrees of freedom fractionalises into monopoles. This enables us to account for a mysterious phase transition observed experimentally in spin ice in a magnetic field, which is a liquid-gas transition of the magnetic monopoles. These monopoles can also be detected by other means, e.g., in an experiment modelled after the celebrated Stanford magnetic monopole search.

  4. Spin glass behavior in FeAl2 

    E-Print Network [OSTI]

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

    2001-01-01T23:59:59.000Z

    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...

  5. Spin glass behavior in FeAl2

    E-Print Network [OSTI]

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

    2001-01-01T23:59:59.000Z

    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...

  6. Dynamic Switching of the Spin Circulation in Tapered Magnetic...

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

    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...

  7. Electrical detection of microwave assisted magnetization reversal by spin pumping

    SciTech Connect (OSTI)

    Rao, Siddharth; Subhra Mukherjee, Sankha; Elyasi, Mehrdad; Singh Bhatia, Charanjit; Yang, Hyunsoo, E-mail: eleyang@nus.edu.sg [Department of Electrical and Computer Engineering and NUSNNI, National University of Singapore, Singapore 117576 (Singapore)

    2014-03-24T23:59:59.000Z

    Microwave assisted magnetization reversal has been investigated in a bilayer system of Pt/ferromagnet by detecting a change in the polarity of the spin pumping signal. The reversal process is studied in two material systems, Pt/CoFeB and Pt/NiFe, for different aspect ratios. The onset of the switching behavior is indicated by a sharp transition in the spin pumping voltage. At a threshold value of the external field, the switching process changes from partial to full reversal with increasing microwave power. The proposed method provides a simple way to detect microwave assisted magnetization reversal.

  8. Modeling spin magnetization transport in a spatially varying magnetic field

    E-Print Network [OSTI]

    Rico A. R. Picone; Joseph L. Garbini; John A. Sidles

    2014-08-13T23:59:59.000Z

    We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment. A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation.

  9. Spin-lattice coupling in uranium dioxide probed by magnetostriction measurements at high magnetic fields (P08358-E001-PF)

    SciTech Connect (OSTI)

    K. Gofryk; M. Jaime

    2014-12-01T23:59:59.000Z

    Conclusions Our preliminary magnetostriction measurements have already shown a strong interplay of lattice dynamic and magnetism in both antiferromagnetic and paramagnetic states, and give unambiguous evidence of strong spin- phonon coupling in uranium dioxide. Further studies are planned to address the puzzling behavior of UO2 in magnetic and paramagnetic states and details of the spin-phonon coupling.

  10. Magnetization plateaus of dipolar spin ice on kagome lattice

    SciTech Connect (OSTI)

    Xie, Y. L.; Wang, Y. L.; Yan, Z. B.; Liu, J.-M., E-mail: liujm@nju.edu.cn [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)

    2014-05-07T23:59:59.000Z

    Unlike spin ice on pyrochlore lattice, the spin ice structure on kagome lattice retains net magnetic charge, indicating non-negligible dipolar interaction in modulating the spin ice states. While it is predicted that the dipolar spin ice on kagome lattice exhibits a ground state with magnetic charge order and ?3?×??3 spin order, our work focuses on the magnetization plateau of this system. By employing the Wang-Landau algorithm, it is revealed that the lattice exhibits the fantastic three-step magnetization in response to magnetic field h along the [10] and [01] directions, respectively. For the h//[1 0] case, an additional ?3/6M{sub s} step, where M{sub s} is the saturated magnetization, is observed in a specific temperature range, corresponding to a new state with charge order and short-range spin order.

  11. Spin microscope based on optically detected magnetic resonance

    DOE Patents [OSTI]

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

    2010-07-13T23:59:59.000Z

    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.

  12. Spin microscope based on optically detected magnetic resonance

    DOE Patents [OSTI]

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

    2009-10-27T23:59:59.000Z

    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.

  13. Spin microscope based on optically detected magnetic resonance

    DOE Patents [OSTI]

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

    2009-11-10T23:59:59.000Z

    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.

  14. Spin microscope based on optically detected magnetic resonance

    DOE Patents [OSTI]

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

    2010-06-29T23:59:59.000Z

    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.

  15. Spin microscope based on optically detected magnetic resonance

    DOE Patents [OSTI]

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

    2007-12-11T23:59:59.000Z

    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.

  16. Electron spin magnetism of zigzag graphene nanoribbon edge states

    SciTech Connect (OSTI)

    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

    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.

  17. Artificial Spin Ice - A New Playground to Better Understand Magnetism...

    Office of Science (SC) Website

    Artificial Spin Ice - A New Playground to Better Understand Magnetism Basic Energy Sciences (BES) BES Home About Research Facilities Science Highlights Benefits of BES Funding...

  18. ONDES DE SPIN MAGNETISM IN THE LIGHT RARE EARTH 'METALS

    E-Print Network [OSTI]

    Boyer, Edmond

    ONDES DE SPIN MAGNETISM IN THE LIGHT RARE EARTH 'METALS A. R. MACKINTOSH H. C. Mrsted Institute terres rares Ikgeres. Abstract. -The magnetic properties of the light rare earth metals are reviewed the last decade, the magnetism of the heavy rare earth metals is now rather well understood. The magnetic

  19. Magnetization process of a single magnetic ring detected by nonlocal spin valve measurement

    E-Print Network [OSTI]

    Otani, Yoshichika

    Magnetization process of a single magnetic ring detected by nonlocal spin valve measurement T of a 200-nm-wide Permalloy ring using a nonlocal spin-valve measurement technique in a lateral geometry state using lateral spin-valve geometry.13­15 The chirality is found to be easily determined from

  20. Bifurcation and chaos in spin-valve pillars in a periodic applied magnetic field

    E-Print Network [OSTI]

    S. Murugesh; M. Lakshmanan

    2009-10-20T23:59:59.000Z

    We study the bifurcation and chaos scenario of the macro-magnetization vector in a homogeneous nanoscale-ferromagnetic thin film of the type used in spin-valve pillars. The underlying dynamics is described by a generalized Landau-Lifshitz-Gilbert (LLG) equation. The LLG equation has an especially appealing form under a complex stereographic projection, wherein the qualitative equivalence of an applied field and a spin-current induced torque is transparent. Recently chaotic behavior of such a spin vector has been identified by Zhang and Li using a spin polarized current passing through the pillar of constant polarization direction and periodically varying magnitude, owing to the spin-transfer torque effect. In this paper we show that the same dynamical behavior can be achieved using a periodically varying applied magnetic field, in the presence of a constant DC magnetic field and constant spin current, which is technically much more feasible, and demonstrate numerically the chaotic dynamics in the system for an infinitely thin film. Further, it is noted that in the presence of a nonzero crystal anisotropy field chaotic dynamics occurs at much lower magnitudes of the spin-current and DC applied field.

  1. Investigation of the magnetic properties of insulating thin films using the longitudinal spin Seebeck effect

    SciTech Connect (OSTI)

    Kehlberger, A., E-mail: kehlberg@uni-mainz.de; Jakob, G.; Kläui, M. [Institute of Physics, University of Mainz, 55099 Mainz (Germany); Onbasli, M. C.; Kim, D. H.; Ross, C. A. [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2014-05-07T23:59:59.000Z

    The longitudinal spin Seebeck effect is used as a detector for the magnetic properties and switching characteristics of magnetic thin insulating films. We use a 300 nm and a 20?nm thick Yttrium Iron Garnet (YIG, Y{sub 3}Fe{sub 5}O{sub 12}) film prepared by pulsed laser deposition and afterwards coated by platinum for the detection of the thermally excited magnons by the inverse spin Hall effect. The inverse spin Hall signals reveal a magnetic uniaxial anisotropy along the direction of the platinum stripe in the thicker film. For the thin film we find a more isotropic behavior, which is complementarily observed using the magnetoresistance occurring at the platinum/YIG interface. We explain our results on the basis of x-ray diffraction data, which reveal a miscut of the substrate and film surface and an expansion of the YIG lattice. Both findings favor a growth-induced magnetic anisotropy that we observe.

  2. Electron vortex beams in a magnetic field and spin filter

    E-Print Network [OSTI]

    Debashree Chowdhury; Banasri Basu; Pratul Bandyopadhyay

    2015-02-25T23:59:59.000Z

    We investigate the propagation of electron vortex beams in a magnetic field. It is pointed out that when electron vortex beams carrying orbital angular momentum propagate in a magnetic field, the Berry curvature associated with the scalar electron moving in a cyclic path around the vortex line is modified from that in free space. This alters the spin-orbit interaction, which affects the propagation of nonparaxial beams. The electron vortex beams with tilted vortex lead to spin Hall effect in free space. In presence of a magnetic field in time space we have spin filtering such that either positive or negative spin states emerge in spin Hall currents with clustering of spin $\\frac{1}{2}$ states.

  3. Pulsed Nuclear Magnetic Resonance: Spin Echoes MIT Department of Physics

    E-Print Network [OSTI]

    Seager, Sara

    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

  4. Platinum dendritic nanoparticles with magnetic behavior

    SciTech Connect (OSTI)

    Li, Wenxian, E-mail: wl240@uowmail.edu.au [Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522 (Australia); Solar Energy Technologies, School of Computing, Engineering, and Mathematics, University of Western Sydney, Penrith NSW 2751 (Australia); Sun, Ziqi; Nevirkovets, Ivan P.; Dou, Shi-Xue [Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522 (Australia); Tian, Dongliang [Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of the Ministry of Education, School of Chemistry and the Environment, Beihang University, Beijing 100191 (China)

    2014-07-21T23:59:59.000Z

    Magnetic nanoparticles have attracted increasing attention for biomedical applications in magnetic resonance imaging, high frequency magnetic field hyperthermia therapies, and magnetic-field-gradient-targeted drug delivery. In this study, three-dimensional (3D) platinum nanostructures with large surface area that features magnetic behavior have been demonstrated. The well-developed 3D nanodendrites consist of plentiful interconnected nano-arms ?4?nm in size. The magnetic behavior of the 3D dendritic Pt nanoparticles is contributed by the localization of surface electrons due to strongly bonded oxygen/Pluronic F127 and the local magnetic moment induced by oxygen vacancies on the neighboring Pt and O atoms. The magnetization of the nanoparticles exhibits a mixed paramagnetic and ferromagnetic state, originating from the core and surface, respectively. The 3D nanodendrite structure is suitable for surface modification and high amounts of drug loading if the transition temperature was enhanced to room temperature properly.

  5. Competing spin pumping effects in magnetic hybrid structures

    SciTech Connect (OSTI)

    Azevedo, A., E-mail: aac@df.ufpe.br; Alves Santos, O.; Fonseca Guerra, G. A.; Cunha, R. O.; Rezende, S. M. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Rodríguez-Suárez, R. [Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago (Chile)

    2014-02-03T23:59:59.000Z

    Pure spin current can be detected by its conversion into charge current in nanometer thick nonmagnetic metal layer with large spin-orbit coupling by means of the inverse spin Hall effect (ISHE). Recently, it has been shown that the metallic ferromagnet Permalloy (Py) can also be used as spin current detector in experiments in which an ISHE voltage is created in a Py layer in contact with the insulating ferromagnet yttrium iron garnet (YIG) under a thermal gradient in the longitudinal spin Seebeck configuration. Here, we report experiments with microwave driven spin pumping in heterostructures made with single crystal YIG film and a nanometer thick Py or Pt layer that show that Py behaves differently than nonmagnetic metals as a spin current detector. The results are attributed to the competition between the spin currents generated by the dynamics of the magnetizations in YIG and in Py, which are exchange coupled at the interface.

  6. Spin flip probability of electron in a uniform magnetic field

    SciTech Connect (OSTI)

    Hammond, Richard T. [Department of Physics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina and Army Research Office, Research Triangle Park, North Carolina 27703 (United States)

    2012-03-19T23:59:59.000Z

    The probability that an electromagnetic wave can flip the spin of an electron is calculated. It is assumed that the electron resides in a uniform magnetic field and interacts with an incoming electromagnetic pulse. The scattering matrix is constructed and the time needed to flip the spin is calculated.

  7. Spontaneous Spin Ordering of a Dirac Spin Liquid in a Magnetic Field

    E-Print Network [OSTI]

    Lee, Patrick A.

    The Dirac spin liquid was proposed to be the ground state of the spin-1/2 kagomé antiferromagnets. In a magnetic field B, we show that the state with Fermi pocket is unstable to the Landau level (LL) state. The LL state ...

  8. Magnetic switching behaviors of orbital states with different magnetic quantum numbers in Au/Fe/MgO multilayer system

    SciTech Connect (OSTI)

    Suzuki, Kosuke, E-mail: kosuzuki@gunma-u.ac.jp; Takubo, Shota; Kato, Tadashi; Yamazoe, Masatoshi; Hoshi, Kazushi; Sakurai, Hiroshi [Department of Electronics and Informatics, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515 (Japan); Homma, Yoshiya [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University, 2145-2 Narita-cho, Oarai-machi, Higashiibaraki-gun, Ibaraki 311-1313 (Japan); Itou, Masayoshi; Sakurai, Yoshiharu [Japan Synchrotron Radiation Research Institute, SPring-8, 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)

    2014-08-18T23:59:59.000Z

    A spin specific magnetic hysteresis (SSMH) curve and an orbital specific magnetic hysteresis (OSMH) curve are obtained for Fe/Au/Fe/MgO multilayers by magnetic Compton scattering and SQUID magnetometer measurements. The SSMH curve with each contribution of magnetic quantum number |m|?=?0, 1, and 2 states is obtained by decomposition analyses of magnetic Compton profiles. Residual magnetization is observed for the SSMH curve with magnetic quantum number |m|?=?0, 2 and the OSMH curve. Although the SQUID magnetometer measurements do not show perpendicular magnetic anisotropy (PMA) in the present Fe/Au/Fe/MgO multilayer film, the SSMH curve with magnetic quantum number |m|?=?0, 2 and OSMH curve show switching behaviors of PMA.

  9. Comment on Magnetic Monopole Excitations in Spin Ice

    E-Print Network [OSTI]

    Subir Ghosh

    2008-01-21T23:59:59.000Z

    It has been proposed recently \\cite{son} that excitations in Spin Ice can be of the form of magnetic monopoles that does not obey the Dirac Quantization Condition. It is also well known \\cite{rj} that the above scenario leads to non-associativity among translation generators. It will be interesting to see how the monopole picture in Spin Ice survives in the light of the latter observation.

  10. SPIN POLARIZED PHOTOELECTRON SPECTROSCOPY AS A PROBE OF MAGNETIC SYSTEMS.

    SciTech Connect (OSTI)

    JOHNSON, P.D.; GUNTHERODT, G.

    2006-11-01T23:59:59.000Z

    Spin-polarized photoelectron spectroscopy has developed into a versatile tool for the study of surface and thin film magnetism. In this chapter, we examine the methodology of the technique and its recent application to a number of different problems. We first examine the photoemission process itself followed by a detailed review of spin-polarization measurement techniques and the related experimental requirements. We review studies of spin polarized surface states, interface states and quantum well states followed by studies of the technologically important oxide systems including half-metallic transition metal oxides, ferromagnet/oxide interfaces and the antiferromagnetic cuprates that exhibit high Tc Superconductivity. We also discuss the application of high-resolution photoemission with spin resolving capabilities to the study of spin dependent self energy effects.

  11. Thermally activated switching of perpendicular magnet by spin-orbit spin torque

    SciTech Connect (OSTI)

    Lee, Ki-Seung [Department of Materials Science and Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Spin Convergence Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Lee, Seo-Won [Department of Materials Science and Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Min, Byoung-Chul [Spin Convergence Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Lee, Kyung-Jin, E-mail: kj-lee@korea.ac.kr [Department of Materials Science and Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Spin Convergence Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 136-713 (Korea, Republic of)

    2014-02-17T23:59:59.000Z

    We theoretically investigate the threshold current for thermally activated switching of a perpendicular magnet by spin-orbit spin torque. Based on the Fokker-Planck equation, we obtain an analytic expression of the switching current, in agreement with numerical result. We find that thermal energy barrier exhibits a quasi-linear dependence on the current, resulting in an almost linear dependence of switching current on the log-scaled current pulse-width even below 10?ns. This is in stark contrast to standard spin torque switching, where thermal energy barrier has a quadratic dependence on the current and the switching current rapidly increases at short pulses. Our results will serve as a guideline to design and interpret switching experiments based on spin-orbit spin torque.

  12. Configuration and temperature dependence of magnetic damping in spin valves

    SciTech Connect (OSTI)

    Joyeux, X.; Devolder, T.; Kim, Joo-Von; Gomez de la Torre, Y.; Eimer, S.; Chappert, C. [Institut d'Electronique Fondamentale, University Paris-Sud, 91405 Orsay (France); UMR8622, CNRS, University Paris-Sud, 91405 Orsay (France)

    2011-09-15T23:59:59.000Z

    Using vector-analyzer ferromagnetic resonance, we have studied the microwave susceptibility of a Py/Co/Cu/Co/MnIr spin valve over a large temperature range (5-450 K) and as a function of the magnetic configuration. An effective magnetization and Gilbert damping constant of 1.1 T and 0.021, respectively, are found for the permalloy free layer, with no discernible variation in temperature observed for either quantities. In contrast, the pinned layer magnetization is reduced by heating, and the exchange bias collapses near a temperature of 450 K. The ferromagnetic resonance linewidth of the free layer increases by 500 MHz when the layer magnetizations are aligned in antiparallel, which is attributed to a configuration-dependent contribution to the damping from spin pumping effects.

  13. Magnetization reversal driven by a spin torque oscillator

    SciTech Connect (OSTI)

    Sbiaa, R., E-mail: rachid@squ.edu.om [Department of Physics, Sultan Qaboos University, P.O. Box 36, PC 123 Muscat (Oman)

    2014-09-01T23:59:59.000Z

    Magnetization reversal of a magnetic free layer under spin transfer torque (STT) effect from a magnetic hard layer with a fixed magnetization direction and an oscillating layer is investigated. By including STT from the oscillating layer with in-plane anisotropy and orthogonal polarizer, magnetization-time dependence of free layer is determined. The results show that the frequency and amplitude of oscillations can be varied by adjusting the current density and magnetic properties. For an optimal oscillation frequency (f{sub opt}), a reduction of the switching time (t{sub 0}) of the free layer is observed. Both f{sub opt} and t{sub 0} increase with the anisotropy field of the free layer.

  14. Magnetism of one-dimensional strongly repulsive spin-1 bosons with antiferromagnetic spin-exchange interaction

    SciTech Connect (OSTI)

    Lee, J. Y.; Guan, X. W. [Department of Theoretical Physics, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Batchelor, M. T. [Department of Theoretical Physics, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Mathematical Sciences Institute, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Lee, C. [Nonlinear Physics Centre and ARC Centre of Excellence for Quantum-Atom Optics, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

    2009-12-15T23:59:59.000Z

    We investigate magnetism and quantum phase transitions in a one-dimensional system of integrable spin-1 bosons with strongly repulsive density-density interaction and antiferromagnetic spin-exchange interaction via the thermodynamic Bethe ansatz method. At zero temperature, the system exhibits three quantum phases: (i) a singlet phase of boson pairs when the external magnetic field H is less than the lower critical field H{sub c1}; (ii) a ferromagnetic phase of atoms in the hyperfine state |F=1, m{sub F}=1> when the external magnetic field exceeds the upper critical field H{sub c2}; and (iii) a mixed phase of singlet pairs and unpaired atoms in the intermediate region H{sub c1}spin fluctuations affect the thermodynamics of the model through coupling the spin bound states to the dressed energy for the unpaired m{sub F}=1 bosons. However, such spin dynamics is suppressed by a sufficiently strong external field at low temperatures. Thus the singlet pairs and unpaired bosons may form a two-component Luttinger liquid in the strong coupling regime.

  15. Superconducting magnetic Wollaston prism for neutron spin encoding

    SciTech Connect (OSTI)

    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

    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.

  16. Spin-polarized transport through domain wall in magnetized graphene

    E-Print Network [OSTI]

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

    2009-04-08T23:59:59.000Z

    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.

  17. Magnetic field enhancement of non-local spin signal in Ni{<_80}Fe{<_20}/Ag lateral spin valves.

    SciTech Connect (OSTI)

    Mihajlovic, G.; Erlingsson, S. I.; Vyborny, K.; Pearson, J. E.; Bader, S. D.; Hoffmann, A. (Center for Nanoscale Materials); ( MSD); (Hitachi Global Storage Tech.); (Reykjavik Univ.); (Acad. Sci. Czech Republic)

    2011-01-01T23:59:59.000Z

    We observe a magnetic-field-induced enhancement of the nonlocal spin signal in Ni{sub 80}Fe{sub 20}/Ag lateral spin valves. The enhancement depends on the bias current polarity but not on the field direction. We present a theoretical model that explains our experimental results, taking into account the electron-spin relaxation of magnetic impurities. We find that the relaxation is about an order of magnitude weaker than Elliott-Yafet relaxation.

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

    E-Print Network [OSTI]

    Alexander J. Silenko

    2014-06-09T23:59:59.000Z

    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.

  19. Spin-orbit torque magnetization switching of a three-terminal perpendicular magnetic tunnel junction

    SciTech Connect (OSTI)

    Cubukcu, Murat; Boulle, Olivier; Drouard, Marc; Mihai Miron, Ioan; Gaudin, Gilles [SPINTEC, UMR 8191, CEA/CNRS/UJF/GINP, INAC, F-38054 Grenoble (France); Garello, Kevin; Onur Avci, Can; Gambardella, Pietro [Department of Materials, ETH Zurich, Hönggerbergring 64, CH-8093 Zürich (Switzerland); Langer, Juergen; Ocker, Berthold [Singulus Technologies, Hanauer Landstr, 103, 63796 Kahl am Main (Germany)

    2014-01-27T23:59:59.000Z

    We report on the current-induced magnetization switching of a three-terminal perpendicular magnetic tunnel junction by spin-orbit torque and its read-out using the tunnelling magnetoresistance (TMR) effect. The device is composed of a perpendicular Ta/FeCoB/MgO/FeCoB stack on top of a Ta current line. The magnetization of the bottom FeCoB layer can be switched reproducibly by the injection of current pulses with density 5?×?10{sup 11}?A/m{sup 2} in the Ta layer in the presence of an in-plane bias magnetic field, leading to the full-scale change of the TMR signal. Our work demonstrates the proof of concept of a perpendicular spin-orbit torque magnetic memory cell.

  20. Phase diagram of magnetic domain walls in spin valve nano-stripes N. Rougemaille,1

    E-Print Network [OSTI]

    Boyer, Edmond

    Phase diagram of magnetic domain walls in spin valve nano-stripes N. Rougemaille,1 V. Uhlí,2, 1 O walls in Co/Cu/Py spin valve nano-stripes (Py: Permalloy), in which the Co layer is mostly single domain Magneto- Resistance. These stacking are called spin valve for a metal spacer layer, and pseudo spin valve

  1. Electrical Detection of Spin Pumping due to the Precessing Magnetization of a Single Ferromagnet

    E-Print Network [OSTI]

    van der Wal, Caspar H.

    Electrical Detection of Spin Pumping due to the Precessing Magnetization of a Single Ferromagnet M of spin pumping, using a lateral normal-metal/ferromagnet/normal- metal device, where a single ferromagnet in ferromagnetic resonance pumps spin-polarized electrons into the normal metal, resulting in spin accumulation

  2. Structure and magnetic behavior of transition metal based ionic liquids

    SciTech Connect (OSTI)

    Del Sesto, Rico E [Los Alamos National Laboratory (LANL); Mccleskey, T [Los Alamos National Laboratory (LANL); Burrell, Anthony K [ORNL; Baker, Gary A [ORNL; Thompson, Joe D. [Los Alamos National Laboratory (LANL); Scott, Brian L. [Los Alamos National Laboratory (LANL); Wilkes, John S [United States Air Force Academy (USAFA), Colorado; Williams, Peg [United States Air Force Academy (USAFA), Colorado

    2008-01-01T23:59:59.000Z

    A series of ionic liquids containing different paramagnetic anions have been prepared and all show paramagnetic behavior with potential applications for magnetic and electrochromic switching as well as novel magnetic transport; also, the tetraalkylphosphonium-based ionic liquids reveal anomalous magnetic behavior.

  3. Implementation of State Transfer Hamiltonians in Spin Chains with Magnetic Resonance Techniques

    E-Print Network [OSTI]

    Cappellaro, Paola

    2014-01-01T23:59:59.000Z

    Nuclear spin systems and magnetic resonance techniques have provided a fertile platform for experimental investigation of quantum state transfer in spin chains. From the first observation of polarization transfer, predating ...

  4. 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer spin valve component investigated by polarized neutron reflectometry

    SciTech Connect (OSTI)

    Callori, S. J., E-mail: sara.callori@ansto.gov.au; Bertinshaw, J. [School of Physics, The University of New South Wales, Sydney, New South Wales 2052 (Australia); Bragg Institute, Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Cortie, D. L. [The Institute for Superconducting and Electronic Materials, The University of Wollongong, Wollongong, New South Wales 2522 (Australia); Bragg Institute, Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Cai, J. W., E-mail: jwcai@aphy.iphy.ac.cn; Zhu, T. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Le Brun, A. P. [Bragg Institute, Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Klose, F. [Bragg Institute, Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Department of Physics and Materials Science, City University of Hong Kong (Hong Kong)

    2014-07-21T23:59:59.000Z

    We have observed 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer system using polarized neutron reflectometry. Magnetometry results show magnetic switching for both the biased and free NiFe layers, the latter of which reverses at low applied fields. As these measurements are only capable of providing information about the total magnetization within a sample, polarized neutron reflectometry was used to investigate the reversal behavior of the NiFe layers individually. Both the non-spin-flip and spin-flip neutron reflectometry signals were tracked around the free NiFe layer hysteresis loop and were used to detail the evolution of the magnetization during reversal. At low magnetic fields near the free NiFe coercive field, a large spin-flip signal was observed, indicating magnetization aligned perpendicular to both the applied field and pinned layer.

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

    E-Print Network [OSTI]

    Boyer, Edmond

    - 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

  6. Gravitational waves interacting with a spinning charged particle in the presence of a uniform magnetic field

    E-Print Network [OSTI]

    D. B. Papadopoulos

    2003-12-23T23:59:59.000Z

    The equations which determine the response of a spinning charged particle moving in a uniform magnetic field to an incident gravitational wave are derived in the linearized approximation to general relativity. We verify that 1) the components of the 4-momentum, 4-velocity and the components of the spinning tensor, both electric and magnetic moments, exhibit resonances and 2) the co-existence of the uniform magnetic field and the GW are responsible for the resonances appearing in our equations. In the absence of the GW, the magnetic field and the components of the spin tensor decouple and the magnetic resonances disappear.

  7. Frequency stabilization of spin-torque-driven oscillations by coupling with a magnetic nonlinear resonator

    SciTech Connect (OSTI)

    Kudo, Kiwamu, E-mail: kiwamu.kudo@toshiba.co.jp; Suto, Hirofumi; Nagasawa, Tazumi; Mizushima, Koichi; Sato, Rie [Corporate Research and Development Center, Toshiba Corporation, Kawasaki 212–8582 (Japan)

    2014-10-28T23:59:59.000Z

    The fundamental function of any oscillator is to produce a waveform with a stable frequency. Here, we show a method of frequency stabilization for spin-torque nano-oscillators (STNOs) that relies on coupling with an adjacent nanomagnet through the magnetic dipole–dipole interaction. It is numerically demonstrated that highly stable oscillations occur as a result of mutual feedback between an STNO and a nanomagnet. The nanomagnet acts as a nonlinear resonator for the STNO. This method is based on the nonlinear behavior of the resonator and can be considered as a magnetic analogue of an optimization scheme in nanoelectromechanical systems. The oscillation frequency is most stabilized when the nanomagnet is driven at a special feedback point at which the feedback noise between the STNO and resonator is completely eliminated.

  8. Magnetic domain wall propagation in a submicron spin-valve stripe: influence of the pinned layer

    E-Print Network [OSTI]

    Boyer, Edmond

    1/10 Magnetic domain wall propagation in a submicron spin-valve stripe: influence of the pinned ferromagnetic spin-valve stripe is investigated using giant magnetoresistance. A notch in the stripe efficiently generated in the vicinity of the notch by the pinned layer of the spin-valve. PACS: 72.25.Ba; 73.43.Qt; 75

  9. Determination of magnetic vortex chirality using lateral spin-valve and Y. Otani

    E-Print Network [OSTI]

    Otani, Yoshichika

    Determination of magnetic vortex chirality using lateral spin-valve geometry T. Kimuraa and Y October 2005 We demonstrate the determination of the vortex chirality using a nonlocal spin-valve measurement technique in a lateral spin valve consisting of a Permalloy Py disk 1 m in diameter and a Py wire

  10. Single Spin Optically Detected Magnetic Resonance with E-Band Microwave Resonators

    E-Print Network [OSTI]

    Nabeel Aslam; Matthias Pfender; Rainer Stöhr; Philipp Neumann; Marc Scheffler; Hitoshi Sumiya; Hiroshi Abe; Shinobu Onoda; Takeshi Ohshima; Junichi Isoya; Jörg Wrachtrup

    2015-03-13T23:59:59.000Z

    Magnetic resonance with ensembles of electron spins is nowadays performed in frequency ranges up to 240 GHz and in corresponding magnetic fields of up to 10 T. However, experiments with single electron and nuclear spins so far only reach into frequency ranges of several 10 GHz, where existing coplanar waveguide structures for microwave (MW) delivery are compatible with single spin readout techniques (e.g. electrical or optical readout). Here, we explore the frequency range up to 90 GHz, respectively magnetic fields of up to $\\approx 3\\,$T for single spin magnetic resonance in conjunction with optical spin readout. To this end, we develop MW resonators with optical single spin access. In our case, rectangular E-band waveguides guarantee low-loss supply of microwaves to the resonators. Three dimensional cavities, as well as coplanar waveguide resonators enhance MW fields by spatial and spectral confinement with a MW efficiency of $1.36\\,\\mathrm{mT/\\sqrt{W}}$. We utilize single NV centers as hosts for optically accessible spins, and show, that their properties regarding optical spin readout known from smaller fields (sensor. Regarding spin based quantum registers, high fields lead to a purer product basis of electron and nuclear spins, which promises improved spin lifetimes. For example, during continuous single-shot readout the $^{14}$N nuclear spin shows second-long longitudinal relaxation times.

  11. Spin Chain in Magnetic Field: Limitations of the Large-N Mean-Field Theory

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

    Wohlfeld, K.; Chen, Cheng-Chien; van Veenendaal, M.; Devereaux, T.P.

    2015-02-01T23:59:59.000Z

    Motivated by the recent success in describing the spin and orbital spectrum of a spin-orbital chain using a large-N mean-field approximation [Phys. Rev. B 91, 165102 (2015)], we apply the same formalism to the case of a spin chain in the external magnetic field. It occurs that in this case, which corresponds to N=2 in the approximation, the large-N mean-field theory cannot qualitatively reproduce the spin excitation spectra at high magnetic fields, which polarize more than 50% of the spins in the magnetic ground state. This, rather counterintuitively, shows that the physics of a spin chain can under some circumstancesmore »be regarded as more complex than the physics of a spin-orbital chain.« less

  12. Spin-Glass Behavior in a Giant Unit Cell Compound Tb117Fe52Ge113.8(1)

    SciTech Connect (OSTI)

    Liu, Jing [Ames Laboratory; Xie, Weiwei [Ames Laboratory; Gschneidner, Karl A [Ames Laboratory; Miller, Gordon J [Ames Laboratory; Pecharsky, Vitalij K [Ames Laboratory

    2014-10-15T23:59:59.000Z

    In this paper we demonstrate evidence of a cluster spin glass in Tb117Fe52Ge113.8(1) (a compound with a giant cubic unit cell) via ac and dc magnetic susceptibility, magnetization, magnetic relaxation and heat capacity measurements. The results clearly show that Tb117Fe52Ge113.8(1) undergoes a spin glass phase transition at the freezing temperature, ~38?K. The good fit of the frequency dependence of the freezing temperature to the critical slowing down model and Vogel-Fulcher law strongly suggest the formation of cluster glass in the Tb117Fe52Ge113.8(1) system. The heat capacity data exhibit no evidence for long-range magnetic order, and yield a large value of Sommerfeld coefficient. The spin glass behavior of Tb117Fe52Ge113.8(1) may be understood by assuming the presence of competing interactions among multiple non-equivalent Tb sites present in the highly complex unit cell.

  13. Spin-glass behavior and anomalous magnetoresistance in ferromagnetic Ge{sub 1-x}Fe{sub x}Te epilayer

    SciTech Connect (OSTI)

    Liu, Jindong [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Department of Materials Science and Engineering and Materials Research Center, Northwestern University, Evanston, Illinois 60208 (United States); Cheng, Xiaomin, E-mail: xmcheng@mail.hust.edu.cn; Tong, Fei; Miao, Xiangshui [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2014-07-28T23:59:59.000Z

    We report that the Ge{sub 1-x}Fe{sub x}Te thin film exhibits spin-glass behavior when the Fe concentration increases to 0.08. A large bifurcation between the zero-field cooling and field cooling temperature-dependent magnetization was observed. The hysteresis loops after zero-field cooling and field cooling show an exchange bias effect. A time-dependent thermoremanent magnetization follows power-law decay, which confirms the existence of spin glass. The anomalous magnetotranport properties present a further evidence for spin-glass behavior and give a freezing temperature T{sub g}???5?K in the Ge{sub 0.92}Fe{sub 0.08}Te thin film.

  14. 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 Soft magnetic, micron-sized thin-film structures with magnetic vortices are intriguing systems...

  15. Dynamic control of spin states in interacting magnetic elements

    DOE Patents [OSTI]

    Jain, Shikha; Novosad, Valentyn

    2014-10-07T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    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

    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)

  17. Ferrofluid spin-up flows from uniform and non-uniform rotating magnetic fields

    E-Print Network [OSTI]

    Khushrushahi, Shahriar Rohinton

    2010-01-01T23:59:59.000Z

    When ferrofluid in a cylindrical container is subjected to a rotating azimuthally directed magnetic field, the fluid "spins up" into an almost rigid-body rotation where ferrofluid nanoparticles have both a linear and an ...

  18. Magnetization dynamics and spin diffusion in semiconductors and metals

    E-Print Network [OSTI]

    Cywi?ski, ?ukasz

    2007-01-01T23:59:59.000Z

    to (III,Mn)V ferromagnetic semiconductors . . . . . . . . .semiconductors . . . . . . . . . . . . . . . . . .Spin di?usion in semiconductors and metals: a general

  19. Dynamic magnetization states of a spin valve in the presence of dc and ac currents: Synchronization, modification, and chaos

    E-Print Network [OSTI]

    Li, Charles

    Dynamic magnetization states of a spin valve in the presence of dc and ac currents: Synchronization and numerical calculations of dynamic magnetization states of a spin valve in the presence of dc and ac currents are expected to appear. In this paper, we consider a simple spin valve as a model system to study the problem

  20. Precessional magnetization induced spin current from CoFeB into Ta

    SciTech Connect (OSTI)

    Jamali, Mahdi; Klemm, Angeline; Wang, Jian-Ping, E-mail: jpwang@umn.edu [Department of Electrical and Computer Engineering, University of Minnesota, 4-174 200 Union Street SE, Minneapolis, Minnesota 55455 (United States)] [Department of Electrical and Computer Engineering, University of Minnesota, 4-174 200 Union Street SE, Minneapolis, Minnesota 55455 (United States)

    2013-12-16T23:59:59.000Z

    The spin dynamics at the interface between the CoFeB and Ta layer has been studied using spin pumping and spin wave characterizations. The spin pumping driven by the ferromagnetic resonance in the CoFeB layer injects a spin current into Ta layer which results in an electromotive force across the Ta layer due to the inverse spin Hall effect. Upon changing the polarity of the bias magnetic field, the polarity of the output voltage inverts and the output voltage increases linearly in respect to the microwave signal power which are consistent with the spin pumping characteristics. The effect of the in-plane magnetization angle on the output voltage has been studied. Furthermore, it is found that the frequency spectrum of the spin Hall voltage is modified by the annealing temperature and the full width at half maximum of the spin pumping increases by more than 40% with the increase of the annealing temperature from 200?°C to 300?°C. The spin Hall angle at the Ta-CoFeB interface is determined to be 0.014, and the damping constant of the CoFeB increases from 0.006 in pure CoFeB to 0.015 in Ta/CoFeB film.

  1. Influence of surface spins on the magnetization of fine maghemite nanoparticles

    SciTech Connect (OSTI)

    Nadeem, K. [Department of Physics, International Islamic University, H-10, Islamabad (Pakistan); Krenn, H. [Institute of Physics, Karl-Franzens University Graz, Universitätsplatz 5, A-8010 Graz (Austria); Szabó, D. V. [Institute for Advanced Materials-Materials Process Technology, Karlsruhe Institute of Technology (KIT), 76021 Karlsruhe (Germany)

    2013-12-16T23:59:59.000Z

    Influence of surface spins on magnetization of maghemite nanoparticles have been studied by using SQUID measurements and also comparison done with theoretical simulations. Surface spin disorder arises in these nanoparticles due to the randomness of surface spins. A model of AC-susceptibility has been used to investigate the experimental results. The comparison between experiment and theory signifies the presence of large effective anisotropy and freezing effects on the surface of maghemite nanoparticles. The enhanced effective anisotropy constant of these nanoparticles as compared to bulk maghemite is due to presence of disordered surface spins.

  2. PHYSICAL REVIEW B 86, 085310 (2012) Spin-polarized electric currents in diluted magnetic semiconductor heterostructures induced

    E-Print Network [OSTI]

    Ganichev, Sergey

    2012-01-01T23:59:59.000Z

    on the study of spin-polarized electric currents in diluted magnetic semiconductor (DMS) quantum wells in diluted magnetic semiconductors (DMS) are currently discussed as a key issue for the developmentPHYSICAL REVIEW B 86, 085310 (2012) Spin-polarized electric currents in diluted magnetic

  3. Confined Dissipative Droplet Solitons in Spin-Valve Nanowires with Perpendicular Magnetic Anisotropy

    E-Print Network [OSTI]

    Hoefer, Mark

    in nanoscale structures for magnetic storage and computation, but dissipative droplet studies have so far been possibilities for the study of low-dimensional solitons and droplet applications in nanostructures. DOI: 10 is achieved in devices known as spin valves (SVs) [5­8], where two magnetic layers are separated

  4. Effective spin-flip scattering in diffusive superconducting proximity systems with magnetic disorder

    E-Print Network [OSTI]

    Skvortsov, Mikhail

    Effective spin-flip scattering in diffusive superconducting proximity systems with magnetic superconductors and normal metals or ferromagnets with magnetic disorder. On the length scales much larger than.45. c, 75.60.Ch, 74.78.Fk I. INTRODUCTION In conventional superconductors S , pairing occurs be- tween

  5. Anomalous magnetic behavior in nanocomposite materials of reduced graphene oxide-Ni/NiFe{sub 2}O{sub 4}

    SciTech Connect (OSTI)

    Kollu, Pratap, E-mail: pk419@cam.ac.uk, E-mail: anirmalagrace@vit.ac.in, E-mail: dhirenb@iitb.ac.in [DST-INSPIRE Faculty, Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076 (India); Prathapani, Sateesh; Varaprasadarao, Eswara K.; Mallick, Sudhanshu; Bahadur, D., E-mail: pk419@cam.ac.uk, E-mail: anirmalagrace@vit.ac.in, E-mail: dhirenb@iitb.ac.in [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076 (India); Santosh, Chella; Grace, Andrews Nirmala, E-mail: pk419@cam.ac.uk, E-mail: anirmalagrace@vit.ac.in, E-mail: dhirenb@iitb.ac.in [Centre for Nanotechnology Research, VIT University, Vellore 632014 (India)

    2014-08-04T23:59:59.000Z

    Magnetic Reduced Graphene Oxide-Nickel/NiFe{sub 2}O{sub 4} (RGO-Ni/NF) nanocomposite has been synthesized by one pot solvothermal method. Respective phase formations and their purities in the composite are confirmed by High Resolution Transmission Electron Microscope and X Ray Diffraction, respectively. For the RGO-Ni/NF composite material finite-size effects lead to the anomalous magnetic behavior, which is corroborated in temperature and field dependent magnetization curves. Here, we are reporting the behavior of higher magnetization values for Zero Field Cooled condition to that of Field Cooled for the RGO-Ni/NF nanocomposite. Also, the observed negative and positive moments in Hysteresis loops at relatively smaller applied fields (100?Oe and 200?Oe) are explained on the basis of surface spin disorder.

  6. Nanoscale magnetic field mapping with a single spin scanning probe magnetometer

    SciTech Connect (OSTI)

    Rondin, L.; Tetienne, J.-P.; Spinicelli, P.; Roch, J.-F.; Jacques, V. [Laboratoire de Photonique Quantique et Moleculaire, Ecole Normale Superieure de Cachan and CNRS UMR 8537, 94235 Cachan Cedex (France); Dal Savio, C.; Karrai, K. [Attocube systems AG, Koeniginstrasse 11A RGB, Munich 80539 (Germany); Dantelle, G. [Laboratoire de Physique de la Matiere Condensee, Ecole Polytechnique and CNRS UMR 7643, 91128 Palaiseau (France); Thiaville, A.; Rohart, S. [Laboratoire de Physique des Solides, Universite Paris-Sud and CNRS UMR 8502, 91405 Orsay (France)

    2012-04-09T23:59:59.000Z

    We demonstrate quantitative magnetic field mapping with nanoscale resolution, by applying a lock-in technique on the electron spin resonance frequency of a single nitrogen-vacancy defect placed at the apex of an atomic force microscope tip. In addition, we report an all-optical magnetic imaging technique which is sensitive to large off-axis magnetic fields, thus extending the operation range of diamond-based magnetometry. Both techniques are illustrated by using a magnetic hard disk as a test sample. Owing to the non-perturbing and quantitative nature of the magnetic probe, this work should open up numerous perspectives in nanomagnetism and spintronics.

  7. Micro-focused Brillouin light scattering study of the magnetization dynamics driven by Spin Hall effect in a transversely magnetized NiFe nanowire

    E-Print Network [OSTI]

    Madami, M; Moriyama, T; Tanaka, K; Siracusano, G; Carpentieri, M; Finocchio, G; Tacchi, S; Ono, T; Carlotti, G

    2015-01-01T23:59:59.000Z

    We employed micro-focused Brillouin light scattering to study the amplification of the thermal spin wave eigenmodes by means of a pure spin current, generated by the spin-Hall effect, in a transversely magnetized Pt(4nm)/NiFe(4nm)/SiO2(5nm) layered nanowire with lateral dimensions 500x2750 nm2. The frequency and the cross section of both the center (fundamental) and the edge spin wave modes have been measured as a function of the intensity of the injected dc electric current. The frequency of both modes exhibits a clear redshift while their cross section is greatly enhanced on increasing the intensity of the injected dc. A threshold-like behavior is observed for a value of the injected dc of 2.8 mA. Interestingly an additional mode, localized in the central part of the nanowire, appears at higher frequency on increasing the intensity of the injected dc above the threshold value. Micromagnetic simulations were used to quantitatively reproduce the experimental results and to investigate the complex non-linear d...

  8. ELECTRON SPIN POLARIZATION : A NEW TOOL IN PHOTOEMISSION AND MAGNETISM

    E-Print Network [OSTI]

    Boyer, Edmond

    . On disordering, magnetic semiconductors exhibit new states in the gap which are found to be singly occupied

  9. Spin polarization and magnetic dichroism in core-level photoemission from ferromagnets

    SciTech Connect (OSTI)

    Menchero, J G [Univ. of California, Berkeley, CA (United States). Dept. of Physics

    1997-05-01T23:59:59.000Z

    In this thesis we present a theoretical investigation of angle- and spin-resolved core-level photoemission from ferromagnetic Fe and Ni. We also consider magneto-dichroic effects due to reversal of the photon helicity or reversal of the sample magnetization direction. In chapter 1, we provide a brief outline of the history of photoemission, and show how it has played an important role in the development of modern physics. We then review the basic elements of the theory of core-level photoemission, and discuss the validity of the some of the commonly-used approximations. In chapter 2, we present a one-electron theory to calculate spin- and angle-resolved photoemission spectra for an arbitrary photon polarization. The Hamiltonian includes both spin-orbit and exchange interactions. As test cases for the theory, we calculate the spin polarization and magnetic dichroism for the Fe 2p core level, and find that agreement with experiment is very good.

  10. Spin 1/2 Particle on a Cylinder with Radial Magnetic Field

    E-Print Network [OSTI]

    C. Chryssomalakos; A. Franco; A. Reyes-Coronado

    2003-07-09T23:59:59.000Z

    We study the motion of a charged quantum particle, constrained on the surface of a cylinder, in the presence of a radial magnetic field. When the spin of the particle is neglected, the system essentially reduces to an infinite family of simple harmonic oscillators, equally spaced along the axis of the cylinder. Interestingly enough, it can be used as a quantum Fourier transformer, with convenient visual output. When the spin 1/2 of the particle is taken into account, a non-conventional perturbative analysis results in a recursive closed form for the corrections to the energy and the wavefunction, for all eigenstates, to all orders in the magnetic moment of the particle. A simple two-state system is also presented, the time evolution of which involves an approximate precession of the spin perpendicularly to the magnetic field. A number of plots highlight the findings while several three-dimensional animations have been made available on the web.

  11. Motion of free spins and NMR imaging without a radio-frequency magnetic field

    E-Print Network [OSTI]

    Kees van Schenk Brill; Jassem Lahfadi; Tarek Khalil; Daniel Grucker

    2015-04-19T23:59:59.000Z

    NMR imaging without any radio-frequency magnetic field is explained by a quantum treatment of independent spin~$\\tfrac 12$. The total magnetization is determined by means of their individual wave function. The theoretical treatment, based on fundamental axioms of quantum mechanics and solving explicitly the Schr\\"{o}dinger equation with the kinetic energy part which gives the motion of free spins, is recalled. It explains the phase shift of the spin noise spectrum with its amplitude compared to the conventional NMR spectrum. Moreover it explains also the relatively good signal to noise ratio of NMR images obtained without a RF pulse. This derivation should be helpful for new magnetic resonance imaging sequences or for developing quantum computing by NMR.

  12. Half-metallic magnetism and the search for better spin valves

    SciTech Connect (OSTI)

    Everschor-Sitte, Karin; Sitte, Matthias; MacDonald, Allan H. [Department of Physics, The University of Texas at Austin, 2515 Speedway, Austin, Texas 78712 (United States)

    2014-08-28T23:59:59.000Z

    We use a previously proposed theory for the temperature dependence of tunneling magnetoresistance to shed light on ongoing efforts to optimize spin valves. First, we show that a mechanism in which spin valve performance at finite temperatures is limited by uncorrelated thermal fluctuations of magnetization orientations on opposite sides of a tunnel junction is in good agreement with recent studies of the temperature-dependent magnetoresistance of high quality tunnel junctions with MgO barriers. Using this insight, we propose a simple formula which captures the advantages for spin-valve optimization of using materials with a high spin polarization of Fermi-level tunneling electrons, and of using materials with high ferromagnetic transition temperatures. We conclude that half-metallic ferromagnets can yield better spin-value performance than current elemental transition metal ferromagnet/MgO systems only if their ferromagnetic transition temperatures exceed ?950?K.

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

    SciTech Connect (OSTI)

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

    2012-01-01T23:59:59.000Z

    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

  14. Dynamical properties of three terminal magnetic tunnel junctions: Spintronics meets spin-orbitronics

    SciTech Connect (OSTI)

    Tomasello, R. [Department of Computer Science, Modeling, Electronics and System Science, University of Calabria, Rende (CS) (Italy)] [Department of Computer Science, Modeling, Electronics and System Science, University of Calabria, Rende (CS) (Italy); Carpentieri, M., E-mail: m.carpentieri@poliba.it [Department of Electrical and Information Engineering, Politecnico of Bari, via E. Orabona 4, I-70125 Bari (Italy); Finocchio, G. [Department of Electronic Engineering, Industrial Chemistry and Engineering, University of Messina, C.da di Dio, I-98166 Messina (Italy)] [Department of Electronic Engineering, Industrial Chemistry and Engineering, University of Messina, C.da di Dio, I-98166 Messina (Italy)

    2013-12-16T23:59:59.000Z

    This Letter introduces a micromagnetic model able to characterize the magnetization dynamics in three terminal magnetic tunnel junctions, where the effects of spin-transfer torque and spin-orbit torque are taken into account. Our results predict that the possibility to separate electrically those two torque sources is very promising from a technological point of view for both next generation of nanoscale spintronic oscillators and microwave detectors. A scalable synchronization scheme based on the parallel connection of those three terminal devices is also proposed.

  15. A study of magnetic anisotropy energy in CuMn spin glass

    E-Print Network [OSTI]

    Allen, Christine Adele

    1986-01-01T23:59:59.000Z

    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...

  16. Spin counting in electrically detected magnetic resonance via low-field defect state mixing

    SciTech Connect (OSTI)

    Cochrane, Corey J.; Lenahan, Patrick M. [The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2014-03-03T23:59:59.000Z

    The work herein describes a method that allows one to measure paramagnetic defect densities in semiconductor and insulator based devices with electrically detected magnetic resonance (EDMR). The method is based upon the mixing of defect states which results from the dipolar coupling of paramagnetic sites at low magnetic fields. We demonstrate the measurement method with spin dependent tunneling in thin film dielectrics; however, the method should be equally applicable to paramagnetic defect density measurements in semiconductors via the more commonly utilized EDMR technique called spin dependent recombination.

  17. In situ magnetic a.nd structural analysis of epitaxial NisoFezothin films for spin-valve heterostructures

    E-Print Network [OSTI]

    Atwater, Harry

    In situ magnetic a.nd structural analysis of epitaxial NisoFezothin films for spin-valve-coupling and giant magnetoresistance (.GMRj in NiseFez,,/Cu multilayers' and spin-valves.' To date, all" Furthermore, FeMn, which is typically used in spin valves to exchange bias one of the ferromagnetic layers

  18. Unusual magnetic hysteresis and the weakened transition behavior induced by Sn substitution in Mn{sub 3}SbN

    SciTech Connect (OSTI)

    Sun, Ying, E-mail: sunying@buaa.edu.cn [Center for Condensed Matter and Materials Physics, Department of Physics, Beihang University, Beijing 100191 (China); International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Guo, Yanfeng; Li, Jun; Wang, Xia [Superconducting Properties Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Tsujimoto, Yoshihiro [Materials Processing Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan); Wang, Cong [Center for Condensed Matter and Materials Physics, Department of Physics, Beihang University, Beijing 100191 (China); Feng, Hai L.; Sathish, Clastin I.; Yamaura, Kazunari, E-mail: yamaura.kazunari@nims.go.jp [Superconducting Properties Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Matsushita, Yoshitaka [Analysis Station, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan)

    2014-01-28T23:59:59.000Z

    Substitution of Sb with Sn was achieved in ferrimagnetic antiperovskite Mn{sub 3}SbN. The experimental results indicate that with an increase in Sn concentration, the magnetization continuously decreases and the crystal structure of Mn{sub 3}Sb{sub 1-x}Sn{sub x}N changes from tetragonal to cubic phase at around x of 0.8. In the doping series, step-like anomaly in the isothermal magnetization was found and this behavior was highlighted at x?=?0.4. The anomaly could be attributed to the magnetic frustration, resulting from competition between the multiple spin configurations in the antiperovskite lattice. Meantime, H{sub c} of 18 kOe was observed at x?=?0.3, which is probably the highest among those of manganese antiperovskite materials reported so far. With increasing Sn content, the abrupt change of resistivity and the sharp peak of heat capacity in Mn{sub 3}SbN were gradually weakened. The crystal structure refinements indicate the weakened change at the magnetic transition is close related to the change of c/a ratio variation from tetragonal to cubic with Sn content. The results derived from this study indicate that the behavior of Mn{sub 3}Sb{sub 1-x}Sn{sub x}N could potentially enhance its scientific and technical applications, such as spin torque transfer and hard magnets.

  19. Circuit-quantum electrodynamics with direct magnetic coupling to single-atom spin qubits in isotopically enriched {sup 28}Si

    SciTech Connect (OSTI)

    Tosi, Guilherme, E-mail: g.tosi@unsw.edu.au; Mohiyaddin, Fahd A.; Morello, Andrea, E-mail: a.morello@unsw.edu.au [Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia. (Australia); Huebl, Hans [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching (Germany); Nanosystems Initiative Munich (NIM), Schellingstr. 4, D-80799 Munich, Germany. (Germany)

    2014-08-15T23:59:59.000Z

    Recent advances in silicon nanofabrication have allowed the manipulation of spin qubits that are extremely isolated from noise sources, being therefore the semiconductor equivalent of single atoms in vacuum. We investigate the possibility of directly coupling an electron spin qubit to a superconducting resonator magnetic vacuum field. By using resonators modified to increase the vacuum magnetic field at the qubit location, and isotopically purified {sup 28}Si substrates, it is possible to achieve coupling rates faster than the single spin dephasing. This opens up new avenues for circuit-quantum electrodynamics with spins, and provides a pathway for dispersive read-out of spin qubits via superconducting resonators.

  20. CMOS Interface Circuits for Spin Tunneling Junction Based Magnetic Random Access Memories

    SciTech Connect (OSTI)

    Ganesh Saripalli

    2002-12-31T23:59:59.000Z

    Magneto resistive memories (MRAM) are non-volatile memories which use magnetic instead of electrical structures to store data. These memories, apart from being non-volatile, offer a possibility to achieve densities better than DRAMs and speeds faster than SRAMs. MRAMs could potentially replace all computer memory RAM technologies in use today, leading to future applications like instan-on computers and longer battery life for pervasive devices. Such rapid development was made possible due to the recent discovery of large magnetoresistance in Spin tunneling junction devices. Spin tunneling junctions (STJ) are composite structures consisting of a thin insulating layer sandwiched between two magnetic layers. This thesis research is targeted towards these spin tunneling junction based Magnetic memories. In any memory, some kind of an interface circuit is needed to read the logic states. In this thesis, four such circuits are proposed and designed for Magnetic memories (MRAM). These circuits interface to the Spin tunneling junctions and act as sense amplifiers to read their magnetic states. The physical structure and functional characteristics of these circuits are discussed in this thesis. Mismatch effects on the circuits and proper design techniques are also presented. To demonstrate the functionality of these interface structures, test circuits were designed and fabricated in TSMC 0.35{micro} CMOS process. Also circuits to characterize the process mismatches were fabricated and tested. These results were then used in Matlab programs to aid in design process and to predict interface circuit's yields.

  1. Measurement of Untruncated Nuclear Spin Interactions via Zero- to Ultra-Low-Field Nuclear Magnetic Resonance

    E-Print Network [OSTI]

    John W. Blanchard; Tobias F. Sjolander; Jonathan P. King; Micah P. Ledbetter; Emma H. Levine; Vikram S. Bajaj; Dmitry Budker; Alexander Pines

    2015-07-09T23:59:59.000Z

    Zero- to ultra-low-field nuclear magnetic resonance (ZULF NMR) provides a new regime for the measurement of nuclear spin-spin interactions free from effects of large magnetic fields, such as truncation of terms that do not commute with the Zeeman Hamiltonian. One such interaction, the magnetic dipole-dipole coupling, is a valuable source of spatial information in NMR, though many terms are unobservable in high-field NMR, and the coupling averages to zero under isotropic molecular tumbling. Under partial alignment, this information is retained in the form of so-called residual dipolar couplings. We report zero- to ultra-low-field NMR measurements of residual dipolar couplings in acetonitrile-2-$^{13}$C aligned in stretched polyvinyl acetate gels. This represents the first investigation of dipolar couplings as a perturbation on the indirect spin-spin $J$-coupling in the absence of an applied magnetic field. As a consequence of working at zero magnetic field, we observe terms of the dipole-dipole coupling Hamiltonian that are invisible in conventional high-field NMR. This technique expands the capabilities of zero- to ultra-low-field NMR and may have applications in precision measurement of subtle physical interactions, chemical analysis, and characterization of local mesoscale structure in materials.

  2. Spin-lattice dynamics simulation of external field effect on magnetic order of ferromagnetic iron

    SciTech Connect (OSTI)

    Chui, C. P. [Department of Electronic and Information Engineering, the Hong Kong Polytechnic University (Hong Kong)] [Department of Electronic and Information Engineering, the Hong Kong Polytechnic University (Hong Kong); Zhou, Yan, E-mail: yanzhou@hku.hk [Department of Physics, the University of Hong Kong (Hong Kong)] [Department of Physics, the University of Hong Kong (Hong Kong)

    2014-03-15T23:59:59.000Z

    Modeling of field-induced magnetization in ferromagnetic materials has been an active topic in the last dozen years, yet a dynamic treatment of distance-dependent exchange integral has been lacking. In view of that, we employ spin-lattice dynamics (SLD) simulations to study the external field effect on magnetic order of ferromagnetic iron. Our results show that an external field can increase the inflection point of the temperature. Also the model provides a better description of the effect of spin correlation in response to an external field than the mean-field theory. An external field has a more prominent effect on the long range magnetic order than on the short range counterpart. Furthermore, an external field allows the magnon dispersion curves and the uniform precession modes to exhibit magnetic order variation from their temperature dependence.

  3. Modelling current-induced magnetization switching in Heusler alloy Co2FeAl-based spin-valve nanopillar

    E-Print Network [OSTI]

    Chen, Long-Qing

    Modelling current-induced magnetization switching in Heusler alloy Co2FeAl-based spin-valve-perpendicular-to-plane pseudo spin-valves using Co2Fe(Ga0.5Ge0.5) Heusler alloy Appl. Phys. Lett. 103, 202401 (2013); 10.1063/1.4829633 Simulation of multilevel cell spin transfer switching in a full-Heusler alloy spin-valve nanopillar Appl

  4. Cyclic behavior of solar inter-network magnetic field

    E-Print Network [OSTI]

    Jin, Chunlan

    2015-01-01T23:59:59.000Z

    Solar inter-network magnetic field is the weakest component of solar magnetism, but contributes most of the solar surface magnetic flux. The study on its origin has been constrained by the inadequate tempo-spatial resolution and sensitivity of polarization observations. With dramatic advances in spatial resolution and detective sensitivity, solar spectro-polarimetry provided by the Solar Optical Telescope aboard Hinode in an interval from solar minimum to maximum of cycle 24 opens an unprecedented opportunity to study the cyclic behavior of solar inter-network magnetic field. More than 1000 Hinode magnetograms observed from 2007 January to 2014 August are selected in the study. It has been found that there is a very slight correlation between sunspot number and magnetic field at the inter-network flux spectrum. From solar minimum to maximum of cycle 24, the flux density of solar inter-network field is invariant, which is 10$\\pm1$ G. The observations suggest that the inter-network magnetic field does not arise...

  5. Topological Invariant and Quantum Spin Models from Magnetic ? Fluxes in Correlated Topological Insulators

    E-Print Network [OSTI]

    F. F. Assaad; M. Bercx; M. Hohenadler

    2013-02-28T23:59:59.000Z

    The adiabatic insertion of a \\pi flux into a quantum spin Hall insulator gives rise to localized spin and charge fluxon states. We demonstrate that \\pi fluxes can be used in exact quantum Monte Carlo simulations to identify a correlated Z_2 topological insulator using the example of the Kane-Mele-Hubbard model. In the presence of repulsive interactions, a \\pi flux gives rise to a Kramers doublet of spinon states with a Curie law signature in the magnetic susceptibility. Electronic correlations also provide a bosonic mode of magnetic excitons with tunable energy that act as exchange particles and mediate a dynamical interaction of adjustable range and strength between spinons. \\pi fluxes can therefore be used to build models of interacting spins. This idea is applied to a three-spin ring and to one-dimensional spin chains. Due to the freedom to create almost arbitrary spin lattices, correlated topological insulators with \\pi fluxes represent a novel kind of quantum simulator potentially useful for numerical simulations and experiments.

  6. Charged spinning fluids with magnetic dipole moment in the Einstein-Cartan theory

    SciTech Connect (OSTI)

    Amorim, R.

    1985-06-15T23:59:59.000Z

    A classical perfect charged spinning fluid with magnetic dipole moment in the Einstein-Cartan theory is described by using an Eulerian Lagrangian formalism. The field equations and equations of motion so obtained generalize those proposed by Ray and Smalley. We also clarify some open questions which appear in the works of Ray and Smalley and of de Ritis et al.

  7. Magnetic order of the iron spins in NdFeAsO

    SciTech Connect (OSTI)

    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

    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

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

    SciTech Connect (OSTI)

    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

    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.

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

    E-Print Network [OSTI]

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

    2014-04-04T23:59:59.000Z

    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.

  10. Spin Equilibria in Monomeric Manganocenes: Solid State Magnetic and EXAFS Studies

    SciTech Connect (OSTI)

    Walter, M. D.; Sofield, C. D.; Booth, C. H.; Andersen, R. A.

    2009-02-09T23:59:59.000Z

    Magnetic susceptibility measurements and X-ray data confirm that tert-butyl-substituted manganocenes [(Me{sub 3}C){sub n}C{sub 5}H{sub 5?n}]{sub 2}Mn (n = 1, 2) follow the trend previously observed with the methylated manganocenes; that is, electron-donating groups attached to the Cp ring stabilize the low-spin (LS) electronic ground state relative to Cp{sub 2}Mn and exhibit higher spin-crossover (SCO) temperatures. However, introducing three CMe{sub 3} groups on each ring gives a temperature-invariant high-spin (HS) state manganocene. The origin of the high-spin state in [1,2,4-(Me{sub 3}C){sub 3}C{sub 5}H{sub 2}]{sub 2}Mn is due to the significant bulk of the [1,2,4-(Me{sub 3}C){sub 3}C{sub 5}H{sub 2}]{sup -} ligand, which is sufficient to generate severe inter-ring steric strain that prevents the realization of the low-spin state. Interestingly, the spin transition in [1,3-(Me{sub 3}C){sub 2}C{sub 5}H{sub 3}]{sub 2}Mn is accompanied by a phase transition resulting in a significant irreversible hysteresis ({Delta}T{sub c} = 16 K). This structural transition was also observed by extended X-ray absorption fine-structure (EXAFS) measurements. Magnetic susceptibility studies and X-ray diffraction data on SiMe{sub 3}-substituted manganocenes [(Me{sub 3}Si){sub n}C{sub 5}H{sub 5-n}]{sub 2}Mn (n = 1, 2, 3) show high-spin configurations in these cases. Although tetra- and hexasubstituted manganocenes are high-spin at all accessible temperatures, the disubstituted manganocenes exhibit a small low-spin admixture at low temperature. In this respect it behaves similarly to [(Me{sub 3}C)(Me{sub 3}Si)C{sub 5}H{sub 3}]{sub 2}Mn, which has a constant low-spin admixture up to 90 K and then gradually converts to high-spin. Thermal spin-trapping can be observed for [(Me{sub 3}C)(Me{sub 3}Si)C{sub 5}H{sub 3}]{sub 2}Mn on rapid cooling.

  11. Surface Magnetization and Critical Behavior of Aperiodic Ising Quantum Chains

    E-Print Network [OSTI]

    L. Turban; F. Igloi; B. Berche

    1997-09-05T23:59:59.000Z

    We consider semi-infinite two-dimensional layered Ising models in the extreme anisotropic limit with an aperiodic modulation of the couplings. Using substitution rules to generate the aperiodic sequences, we derive functional equations for the surface magnetization. These equations are solved by iteration and the surface magnetic exponent can be determined exactly. The method is applied to three specific aperiodic sequences, which represent different types of perturbation, according to a relevance-irrelevance criterion. On the Thue-Morse lattice, for which the modulation is an irrelevant perturbation, the surface magnetization vanishes with a square root singularity, like in the homogeneous lattice. For the period-doubling sequence, the perturbation is marginal and the surface magnetic exponent varies continuously with the modulation amplitude. Finally, the Rudin-Shapiro sequence, which corresponds to the relevant case, displays an anomalous surface critical behavior which is analyzed via scaling considerations: Depending on the value of the modulation, the surface magnetization either vanishes with an essential singularity or remains finite at the bulk critical point, i.e., the surface phase transition is of first order.

  12. Magnetic response of energy levels of superconducting nanoparticles with spin-orbit scattering

    E-Print Network [OSTI]

    Nesterov, Konstantin N

    2015-01-01T23:59:59.000Z

    Discrete energy levels of ultrasmall metallic grains are extracted in single-electron-tunneling-spectroscopy experiments. We study the response of these energy levels to an external magnetic field in the presence of both spin-orbit scattering and pairing correlations. In particular, we investigate $g$-factors and level curvatures that parametrize, respectively, the linear and quadratic terms in the magnetic-field dependence of the many-particle energy levels of the grain. Both of these quantities exhibit level-to-level fluctuations in the presence of spin-orbit scattering. We show that the distribution of $g$-factors is not affected by the pairing interaction and that the distribution of level curvatures is sensitive to pairing correlations even in the smallest grains in which the pairing gap is smaller than the mean single-particle level spacing. We propose the level curvature in a magnetic field as a tool to probe pairing correlations in tunneling spectroscopy experiments.

  13. Magnetic charge crystals imaged in artificial spin ice

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

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of Science (SC)Integrated Codes |IsLove Your Home and It'll Love YouTokamak| NationalMagneticMagnetic

  14. Dynamic Switching of the Spin Circulation in Tapered Magnetic Nanodisks

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

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625govInstrumentstdmadapInactiveVisitingContract ManagementDiscovering HowAnaDynamic Switching of the Spin Circulation

  15. Scanning localized magnetic fields in a microfluidic device using single spin in a nano-diamond

    E-Print Network [OSTI]

    Lim, Kangmook; Shapiro, Benjamin; Taylor, Jacob M; Waks, Edo

    2014-01-01T23:59:59.000Z

    Nitrogen vacancy (NV) color centers in diamond have emerged as highly versatile optical emitters that exhibit room temperature spin properties. These characteristics make NV centers ideal for magnetometry which plays an important role in a broad range of chemical and biological sensing applications. The integration of NV magnetometers with microfluidic systems could enable the study of isolated chemical and biological samples in a fluid environment with high spatial resolution. Here we demonstrate a method to perform localized magnetometry with nanometer spatial precision using a single NV center in a microfluidic device. We manipulate a magnetic particle within a liquid environment using a combination of planar flow control and vertical magnetic actuation to achieve 3-dimensional manipulation. A diamond nanocrystal containing a single NV center is deposited in the microfluidic channels and acts as a local magnetic field probe. We map out the magnetic field distribution of the magnetic particle by varying its...

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

    SciTech Connect (OSTI)

    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

    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.

  17. Generalized Uhlenbeck-Goudsmit hypothesis 'Magnetic' S^{a} and 'Electric' Z^{a} Spins

    E-Print Network [OSTI]

    Tomislav Ivezic

    2010-03-23T23:59:59.000Z

    In this paper, the connection between the dipole moment tensor D^{ab} and the spin four-tensor S^{ab} is formulated in the form of the generalized Uhlenbeck-Goudsmit hypothesis, D^{ab}=g_{S}S^{ab}. It is also found that the spin four-tensor S^{ab} can be decomposed into two 4-vectors, the usual `space-space' intrinsic angular momentum S^{a}, which will be called `magnetic' spin (mspin), and a new one, the `time-space' intrinsic angular momentum Z^{a}, which will be called `electric' spin (espin). Both spins are equally good physical quantities. Taking into account the generalized Uhlenbeck-Goudsmit hypothesis, the decomposition of S^{ab} and the decomposition of D^{ab} into the dipole moments m^{a} and d^{a}, we find that an electric dipole moment (EDM) of a fundamental particle, as a four-dimensional (4D) geometric quantity, is determined by Z^{a} and not, as generally accepted, by the spin $\\mathbf{S}$ as a 3-vector. Also it is shown that neither the T inversion nor the P inversion are good symmetries in the 4D spacetime. In this geometric approach, only the world parity W, Wx^{a}=-x^{a}, is well defined in the 4D spacetime. Some consequences for elementary particle theories and experiments that search for EDM are briefly discussed.

  18. NEUTRINO SPIN AND FLAVOUR CONVERSION AND OSCILLATIONS IN MAGNETIC FIELD

    E-Print Network [OSTI]

    A. M. Egorov; G. G. Likhachev; A. I. Studenikin

    1995-06-09T23:59:59.000Z

    A review of the neutrino conversion and oscillations among the two neutrino species (active and sterile) induced by strong twisting magnetic field is presented and implications to neutrinos in neutron star, supernova, the Sun and interstellar galactic media are discussed. The ``cross-boundary effect" (CBE) (i.e., a possible conversion of one half of neutrinos of the bunch from active into sterile specie) at the surface of neutron star is also studied for a realistic neutron star structure.

  19. Long-range ordering of reduced magnetic moments in the spin-gap compound CeOs{sub 2}Al{sub 10} as seen via muon spin relaxation and neutron scattering

    SciTech Connect (OSTI)

    Adroja, D. T.; Hillier, A. D.; Kockelmann, W. A.; Anand, V. K.; Stewart, J. R.; Taylor, J. [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot Oxon OX11 0QX (United Kingdom); Deen, P. P. [Institute Laue-Langevin, BP 156, 6 Rue Jules Horowitz, 38042 Grenoble Cedex (France); Strydom, A. M. [Physics Department, University of Johannesburg, P.O. Box 524, Auckland Park 2006 (South Africa); Muro, Y.; Kajino, J.; Takabatake, T. [Department of Quantum Matter, ADSM, and IAMR, Hiroshima University, Higashi-Hiroshima 739-8530 (Japan)

    2010-09-01T23:59:59.000Z

    We have carried out neutron diffraction, muon spin relaxation ({mu}SR), and inelastic neutron scattering (INS) investigations on a polycrystalline sample of CeOs{sub 2}Al{sub 10} to investigate the nature of the phase transition observed near 29 K in the resistivity and heat capacity. Our {mu}SR data clearly reveal coherent frequency oscillations below 28 K, indicating the presence of an internal field at the muon site, which confirms the long-range magnetic ordering of the Ce moment below 28 K. Upon cooling the sample below 15 K, unusual behavior of the temperature-dependent {mu}SR frequencies may indicate either a change in the muon site, consistent with the observation of superstructure reflections in electron diffraction, or a change in the ordered magnetic structure. Neutron diffraction data do not reveal any clear sign of either magnetic Bragg peaks or superlattice reflections. Furthermore, INS measurements clearly reveal the presence of a sharp inelastic excitation near 11 meV between 5 and 26 K, due to opening of a gap in the spin-excitation spectrum, which transforms into a broad response at and above 30 K. The magnitude of the spin gap (11 meV) as derived from the INS peak position agrees very well with the gap value as estimated from the bulk properties.

  20. Non-Markovian spin transfer dynamics in magnetic semiconductors despite short memory times

    E-Print Network [OSTI]

    Christoph Thurn; Moritz Cygorek; Vollrath Martin Axt; Tilmann Kuhn

    2013-03-18T23:59:59.000Z

    A quantum kinetic theory of the spin transfer between carriers and Mn atoms in a Mn doped diluted magnetic semiconductor is presented. It turns out that the typical memory time associated with these processes is orders of magnitude shorter than the time scale of the spin transfer. Nevertheless, Markovian rate equations, which are obtained by neglecting the memory, work well only for bulk systems. For quantum wells and wires the quantum kinetic results qualitatively deviate from the Markovian limit under certain conditions. Instead of a monotonic decay of an initially prepared excess electron spin, an overshoot or even coherent oscillations are found. It is demonstrated that these features are caused by energetic redistributions of the carriers due to the energy-time uncertainty.

  1. Numerical methods for computing the ground state of spin-1 Bose-Einstein condensates in a uniform magnetic field

    E-Print Network [OSTI]

    Bao, Weizhu

    Numerical methods for computing the ground state of spin-1 Bose-Einstein condensates in a uniform for computing the ground-state solution of spin-1 Bose-Einstein condensates subjected to a uniform magnetic to compute the condensate ground state in a harmonic plus optical lattice potential, and the effect

  2. Dependence of dynamic magnetization and magneto-transport properties of FeAlSi films with oblique sputtering studied via spin rectification effect

    SciTech Connect (OSTI)

    Soh, Wee Tee; Ong, C. K. [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive 3, Singapore 117551 (Singapore); Zhong, Xiaoxi, E-mail: xiaoxi.zhong@gmail.com [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive 3, Singapore 117551 (Singapore); School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China)

    2014-09-15T23:59:59.000Z

    FeAlSi (Sendust) is known to possess excellent soft magnetic properties comparable to traditional soft magnetic alloys such as NiFe (Permalloy), while having a relatively higher resistance for lower eddy current losses. However, their dynamic magnetic and magneto-transport properties are not well-studied. Via the spin rectification effect, we electrically characterize a series of obliquely sputtered FeAlSi films at ferromagnetic resonance. The variations of the anisotropy fields and damping with oblique angle are extracted and discussed. In particular, two-magnon scattering is found to dominate the damping behavior at high oblique angles. An analysis of the results shows large anomalous Hall effect and anisotropic magneto-resistance across all samples, which decreases sharply with increasing oblique incidence.

  3. Overcoming inherent magnetic instability, preventing spin canting and magnetic coding in an assembly of ferrimagnetic nanoparticles

    SciTech Connect (OSTI)

    Dey, S.; Kumar, S., E-mail: kumars@phys.jdvu.ac.in [Department of Physics, Jadavpur University, Kolkata 700032 (India); Dey, S. K. [Department of Physics, Jadavpur University, Kolkata 700032 (India); Department of Physics, NITMAS, 24 Pargana (s) 743368 (India); Bagani, K.; Banerjee, S. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Majumder, S. [Department of Physics, Jadavpur University, Kolkata 700032 (India); Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Roychowdhury, A.; Das, D. [UGC-DAE CSR, Kolkata Centre, III/LB-8, Bidhannagar, Kolkata 700098 (India); Reddy, V. R. [UGC-DAE CSR, University Campus, Khandwa Road, Indore 452001 (India)

    2014-08-11T23:59:59.000Z

    The authors find that for mechanically milled Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} (?10?nm), the mechanical strain induced enhancement of anisotropy energy helps to retain stable magnetic order. The reduction of magnetization can be prevented by keeping the cation distribution of nanometric ferrites at its equilibrium ratio. Moreover, the sample can be used in coding, storing, and retrieving of binary bit (“0” and “1”) through magnetic field change.

  4. Spin-lozenge thermodynamics and magnetic excitations in Na3RuO4

    SciTech Connect (OSTI)

    Haraldsen, Jason T [ORNL; Stone, Matthew B [ORNL; Lumsden, Mark D [ORNL; Barnes, Ted {F E } [ORNL; Jin, Rongying [ORNL; Taylor, J. W. [ISIS Facility, Rutherford Appleton Laboratory; Fernandez-Alonso, F [ISIS Facility, Rutherford Appleton Laboratory

    2009-01-01T23:59:59.000Z

    We report inelastic and elastic neutron scattering, magnetic susceptibility, and heat capacity measurements of polycrystalline sodium ruthenate (Na3RuO4). Previous work suggests this material consists of isolated tetramers of S = 3/2 Ru5+ ions in a so-called lozenge configuration. Using a Heisenberg antiferromagnet Hamiltonian, we analytically determine the energy eigenstates for general spin S. From this model, the neutron scattering cross-sections for excitations associated with spin-3/2 tetramer configurations is determined. Comparison of magnetic susceptibility and inelastic neutron scattering results shows that the proposed lozenge model is not distinctly supported, but provides evidence that the system may be better described as a pair of non-interacting inequivalent dimers, i.e double dimers. However, the existence of long-range magnetic order below Tc ? 28 K immediately questions such a description. Although no evidence of the lozenge model is observed, future studies on single crystals may further clarify the appropriate magnetic Hamiltonian.

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

    SciTech Connect (OSTI)

    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

    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.

  6. Anisotropic magnetodielectric coupling behavior of Ca{sub 3}Co{sub 1.4}Rh{sub 0.6}O{sub 6} due to geometrically frustrated magnetism

    SciTech Connect (OSTI)

    Basu, Tathamay; Iyer, Kartik K.; Singh, Kiran; Mukherjee, K.; Paulose, P. L.; Sampathkumaran, E. V. [Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005 (India)

    2014-09-08T23:59:59.000Z

    We have investigated the magnetic, dielectric, and magnetodielectric (MDE) behavior of a geometrically frustrated spin-chain system, Ca{sub 3}Co{sub 1.4}Rh{sub 0.6}O{sub 6} (related to Ca{sub 3}CoRhO{sub 6}), in the single crystalline form for different orientations. The results bring out that the magnetic behavior of this compound is by itself interesting in the sense that this compound exhibits an anisotropic glassy-like magnetic behavior with a huge frequency (?) dependence of ac susceptibility (?) peak for an orientation along the spin-chain in the range of 30–60?K; this behavior is robust to applications of large external magnetic fields (H) unlike in canonical spin-glasses. The temperature dependence of dielectric constant also shows strong ?-dependence with similar robustness to H. The isothermal H-dependent dielectric results at low temperatures establish anisotropic MDE coupling. It is intriguing to note that there is a “step” roughly at one-third of saturation values as in the case of isothermal magnetization curves for same temperatures (for orientation along spin-chain), a correlation hitherto unrealized for geometrically frustrated systems.

  7. Rotor Design for High Pressure Magic Angle Spinning Nuclear Magnetic Resonance

    SciTech Connect (OSTI)

    Turcu, Romulus V.F.; Hoyt, David W.; Rosso, Kevin M.; Sears, Jesse A.; Loring, John S.; Felmy, Andrew R.; Hu, Jian Z.

    2013-01-01T23:59:59.000Z

    High pressure magic angle spinning (MAS) nuclear magnetic resonance (NMR) with a sample spinning rate exceeding 2.1 kHz and pressure greater than 165 bar has never been realized. In this work, a new sample cell design is reported, suitable for constructing cells of different sizes. Using a 7.5 mm high pressure MAS rotor as an example, internal pressure as high as 200 bar at a sample spinning rate of 6 kHz is achieved. The new high pressure MAS rotor is re-usable and compatible with most commercial NMR set-ups, exhibiting low 1H and 13C NMR background and offering maximal NMR sensitivity. As an example of its many possible applications, this new capability is applied to determine reaction products associated with the carbonation reaction of a natural mineral, antigorite ((Mg,Fe2+)3Si2O5(OH)4), in contact with liquid water in water-saturated supercritical CO2 (scCO2) at 150 bar and 50 deg C. This mineral is relevant to the deep geologic disposal of CO2, but its iron content results in too many sample spinning sidebands at low spinning rate. Hence, this chemical system is a good case study to demonstrate the utility of the higher sample spinning rates that can be achieved by our new rotor design. We expect this new capability will be useful for exploring solid-state, including interfacial, chemistry at new levels of high-pressure in a wide variety of fields.

  8. Magnetic Fields in Blazar Pc-scale Jets - Possible connection to Spin Rates of Black holes ?

    E-Print Network [OSTI]

    P. Kharb; M. L. Lister; P. Shastri

    2008-03-06T23:59:59.000Z

    We re-examine the differences observed in the pc-scale magnetic field geometry of high and low optical polarization Quasars (HPQs, LPRQs) using the MOJAVE sample. We find that, as previously reported, HPQ jets exhibit predominantly transverse B fields while LPRQ jets tend to display longitudinal B fields. We attempt to understand these results along with the different B field geometry observed in the low and high energy peaked BL Lacs (LBLs, HBLs) using a simple picture wherein the spinning central black holes in these AGNs influence the speed and strength of the jet components (spine, sheath). Higher spin rates in HPQs compared to LPRQs and LBLs compared to HBLs could explain the different total radio powers, VLBI jet speeds, and the observed B field geometry in these AGN classes.

  9. Magnetic anisotropy barrier for spin tunneling in Mn{sub 12}O{sub 12} molecules

    SciTech Connect (OSTI)

    Pederson, M.R. [Center for Computational Materials Science--6392, Naval Research Laboratory, Washington, D.C. 20375-5000 (United States)] [Center for Computational Materials Science--6392, Naval Research Laboratory, Washington, D.C. 20375-5000 (United States); Khanna, S.N. [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000 (United States)] [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284-2000 (United States)

    1999-10-01T23:59:59.000Z

    Electronic structure calculations on the nature of electronic states and the magnetic coupling in Mn-acetate [Mn{sub 12}O{sub 12}(RCOO){sub 16}(H{sub 2}O){sub 4}] molecules have been been carried out within the generalized gradient approximation to the density functional formalism. Our studies on this 100-atom molecule illustrate the role of the nonmagnetic carboxyl host in stabilizing the ferrimagnetic Mn{sub 12}O{sub 12} core and provide estimates of the local magnetic moment at the various sites. We provide a first density-functional-based prediction of the second-order magnetic anisotropy energy of this system. Results are in excellent agreement with experiment. To perform these calculations we introduce a simplified exact method for spin-orbit coupling and magnetic anisotropy energies in multicenter systems. This method is free of shape approximations and has other advantages as well. First, it is valid for periodic boundary conditions or finite systems and is independent of basis set choice. Second, the method does not require the calculation of electric field. Third, for applications to systems with a finite energy gap between occupied and unoccupied electronic states, a perturbative expansion allows for a simple determination of the magnetic anisotropy energy. {copyright} {ital 1999} {ital The American Physical Society}

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

    E-Print Network [OSTI]

    Hu, Chia-Ren; HAM, TE.

    1981-01-01T23:59:59.000Z

    PHYSICAL REVIE%' B VOLUME 24, NUMBER 5 1 SEPTEMBER 1981 Nonlinear magnetic ringing of spin-ordered solid He Chia-Ren Hu and Thomas E. Ham Departn~ent of'Physics, Texas 3 c6 M University, College Station, Texas 77843 (Received 24 October 1980... derivative of d. If Eqs; (2) and (3) are first linearized around the equilibrium solution for / H =cosH (where H ?= H/H), viz. , yS =yaH, d l = d S =0, and l S =cosH, the resulting equa- tions then describe the undamped resonance modes of frequencies...

  11. Parametric excitation in a magnetic tunnel junction-based spin torque oscillator

    SciTech Connect (OSTI)

    Dürrenfeld, P.; Iacocca, E. [Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); Åkerman, J. [Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); Materials Physics, School of ICT, KTH-Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Muduli, P. K. [Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); Department of Physics, Indian Institute of Technology, Delhi, 110016 New Delhi (India)

    2014-02-03T23:59:59.000Z

    Using microwave current injection at room temperature, we demonstrate parametric excitation of a magnetic tunnel junction (MTJ)-based spin-torque oscillator (STO). Parametric excitation is observed for currents below the auto-oscillation threshold, when the microwave current frequency f{sub e} is twice the STO free-running frequency f{sub 0}. Above threshold, the MTJ becomes parametrically synchronized. In the synchronized state, the STO exhibits an integrated power up to 5 times higher and a linewidth reduction of two orders of magnitude, compared to free-running conditions. We also show that the parametric synchronization favors single mode oscillations in the case of multimode excitation.

  12. Perpendicular spin transfer torque magnetic random access memories with high spin torque efficiency and thermal stability for embedded applications (invited)

    SciTech Connect (OSTI)

    Thomas, Luc, E-mail: luc.thomas@headway.com; Jan, Guenole; Zhu, Jian; Liu, Huanlong; Lee, Yuan-Jen; Le, Son; Tong, Ru-Ying; Pi, Keyu; Wang, Yu-Jen; Shen, Dongna; He, Renren; Haq, Jesmin; Teng, Jeffrey; Lam, Vinh; Huang, Kenlin; Zhong, Tom; Torng, Terry; Wang, Po-Kang [TDK-Headway Technologies, Inc., Milpitas, California 95035 (United States)

    2014-05-07T23:59:59.000Z

    Magnetic random access memories based on the spin transfer torque phenomenon (STT-MRAMs) have become one of the leading candidates for next generation memory applications. Among the many attractive features of this technology are its potential for high speed and endurance, read signal margin, low power consumption, scalability, and non-volatility. In this paper, we discuss our recent results on perpendicular STT-MRAM stack designs that show STT efficiency higher than 5?k{sub B}T/?A, energy barriers higher than 100?k{sub B}T at room temperature for sub-40?nm diameter devices, and tunnel magnetoresistance higher than 150%. We use both single device data and results from 8?Mb array to demonstrate data retention sufficient for automotive applications. Moreover, we also demonstrate for the first time thermal stability up to 400?°C exceeding the requirement of Si CMOS back-end processing, thus opening the realm of non-volatile embedded memory to STT-MRAM technology.

  13. Magnetic Order and Ferroelectricity in RMnO3 Multiferroic Manganites: Coupline Between R- and Mn-spins

    SciTech Connect (OSTI)

    Aliouane, N.; Prokhnenko, O; Feyerherm, R; Mostovoy, M; Strempfer, J; Habicht, K; Rule, K; Dudzik, E; Wolter, A; et. al.

    2008-01-01T23:59:59.000Z

    Combining polarized and unpolarized neutron scattering techniques with x-ray resonant magnetic scattering we have studied the coupling between the Mn- and R-spin-ordering in the multiferroic RMnO3, R = Tb and Dy. Polarized neutron diffraction reveals the moment orientation associated with the various modes describing the complex magnetic ordering observed in TbMnO3, while neutron diffraction in high magnetic fields allows the identification of the origin (Mn versus Tb) of the various modes. In this way we identify significant Cx and Fz contributions from Tb arising from the coupling of Tb moments to the Mn cycloidal ordering. The x-ray studies give further insight into this coupling. In the ferroelectric phase, both TbMnO3 and DyMnO3 show an induced ordering of the R-ion with a propagation vector clamped to the Mn ordering. While in TbMnO3 this clamping leads to a ground state in which the two propagation vectors tTb and tMn obey the relation 3tTb-tMn = 1, in DyMnO3 the ferroelectric polarization is effectively enhanced. The theoretical analysis of these effects not only explains the observed behavior for R = Tb and Dy but can also be applied to understand the Mn-R interaction in the related compounds with R = Gd and Ho. Finally we show both experimentally and theoretically how the Mn-R coupling can enhance the ferroelectric polarization in this manganite's multiferroics.

  14. Chains with loops - synthetic magnetic fluxes and topological order in one-dimensional spin systems

    E-Print Network [OSTI]

    Tobias Grass; Christine Muschik; Alessio Celi; Ravindra Chhajlany; Maciej Lewenstein

    2015-04-14T23:59:59.000Z

    Engineering topological quantum order has become a major field of physics. Many advances have been made by synthesizing gauge fields in cold atomic systems. Here, we carry over these developments to other platforms which are extremely well suited for quantum engineering, namely trapped ions and nano-trapped atoms. Since these systems are typically one-dimensional, the action of artificial magnetic fields has so far received little attention. However, exploiting the long-range nature of interactions, loops with non-vanishing magnetic fluxes become possible even in one-dimensional settings. This gives rise to intriguing phenomena, such as fractal energy spectra, flat bands with localized edge states, and topological many-body states. We elaborate on a simple scheme for generating the required artificial fluxes by periodically driving an XY spin chain. Concrete estimates demonstrating the experimental feasibility for trapped ions and atoms in waveguides are given.

  15. Fast, High Fidelity Quantum Dot Spin Initialization without a Strong Magnetic Field by Two-Photon Processes

    E-Print Network [OSTI]

    Arka Majumdar; Ziliang Lin; Andrei Faraon; Jelena Vuckovic

    2009-07-20T23:59:59.000Z

    We describe a proposal for fast electron spin initialization in a negatively charged quantum dot coupled to a microcavity without the need for a strong magnetic field. We employ two-photon excitation to access trion states that are spin forbidden by one-photon excitation. Our simulation shows a maximum initialization speed of 1.3 GHz and maximum fidelity of 99.7% with realistic system parameters.

  16. Investigation of magnetic spin glass property in La{sub 0.5}Bi{sub 0.5}MnO{sub 3} sample using non-linear AC susceptibility measurements

    SciTech Connect (OSTI)

    Kumar, Punith V., E-mail: drvldayal@gmail.com; Manju, M. R., E-mail: drvldayal@gmail.com; Dayal, Vijaylakshmi, E-mail: drvldayal@gmail.com [Department of Physics, Maharaja Institute of Technology, Mysore-571438, Karnataka (India)

    2014-04-24T23:59:59.000Z

    We present a comprehensive study on origin of Spin Glass (SG) property in polycrystalline La{sub 0.5}Bi{sub 0.5}MnO{sub 3} perovskite oxide using linear and higher order ac susceptibility (?) measurements. The third order harmonic susceptibility (?{sub 3}) vs. temperature (K) with varying magnetic fields from 0.95 to 9.45 Oe and the divergence in their ?{sub 3} (max) allows us to infer the SG behavior occurring in the sample possibly due to co-operative freezing of the spins.

  17. Advanced slow-magic angle spinning probe for magnetic resonance imaging and spectroscopy

    DOE Patents [OSTI]

    Wind, Robert A.; Hu, Jian Zhi; Minard, Kevin R.; Rommereim, Donald N.

    2006-01-24T23:59:59.000Z

    The present invention relates to a probe and processes useful for magnetic resonance imaging and spectroscopy instruments. More particularly, the invention relates to a MR probe and processes for obtaining resolution enhancements of fluid objects, including live specimens, using an ultra-slow (magic angle) spinning (MAS) of the specimen combined with a modified phase-corrected magic angle turning (PHORMAT) pulse sequence. Proton NMR spectra were measured of the torso and the top part of the belly of a female BALBc mouse in a 2T field, while spinning the animal at a speed of 1.5 Hz. Results show that even in this relatively low field with PHORMAT, an isotropic spectrum is obtained with line widths that are a factor 4.6 smaller than those obtained in a stationary mouse. Resolution of 1H NMR metabolite spectra are thus significantly enhanced. Results indicate that PHORMAT has the potential to significantly increase the utility of 1H NMR spectroscopy for in vivo biochemical, biomedical and/or medical applications involving large-sized biological objects such as mice, rats and even humans within a hospital setting. For small-sized objects, including biological objects, such as excised tissues, organs, live bacterial cells, and biofilms, use of PASS at a spinning rate of 30 Hz and above is preferred.

  18. Micromagnetic simulations of spin-wave normal modes and the spin-transfer-torque driven magnetization dynamics of a ferromagnetic cross

    SciTech Connect (OSTI)

    Pramanik, Tanmoy, E-mail: pramanik.tanmoy@utexas.edu; Roy, Urmimala; Register, Leonard F.; Banerjee, Sanjay K. [Microelectronics Research Center, University of Texas at Austin, Texas 78758 (United States); Tsoi, Maxim [Physics Department, University of Texas at Austin, Texas 78712 (United States)

    2014-05-07T23:59:59.000Z

    We studied spin-transfer-torque (STT) switching of a cross-shaped magnetic tunnel junction in a recent report [Roy et al., J. Appl. Phys. 113, 223904 (2013)]. In that structure, the free layer is designed to have four stable energy states using the shape anisotropy of a cross. STT switching showed different regions with increasing current density. Here, we employ the micromagnetic spectral mapping technique in an attempt to understand how the asymmetry of cross dimensions and spin polarization direction of the injected current affect the magnetization dynamics. We compute spatially averaged frequency-domain spectrum of the time-domain magnetization dynamics in the presence of the current-induced STT term. At low currents, the asymmetry of polarization direction and that of the arms are observed to cause a splitting of the excited frequency modes. Higher harmonics are also observed, presumably due to spin-wave wells caused by the regions of spatially non-uniform effective magnetic field. The results could be used towards designing a multi-bit-per-cell STT-based random access memory with an improved storage density.

  19. Coordinate Bethe ansatz computation for low temperature behavior of a triangular lattice of a spin-1 Heisenberg antiferromagnet

    SciTech Connect (OSTI)

    Shuaibu, A. [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia and Physics Department, Faculty of Science, Nigerian Defence Academy, P.M.B 2109, Kaduna (Nigeria); Rahman, M. M. [Physics Department, Faculty of Science, Nigerian Defence Academy, P.M.B 2109, Kaduna (Nigeria)

    2014-03-05T23:59:59.000Z

    We study the low temperature behavior of a triangular lattice quantum spin-1 Heisenberg antiferromagnet with single-site anisotropy by using coordinate Bethe ansatz method. We compute the standard two-particle Hermitian Hamiltonian, and obtain the eigenfunctions and eigenvalue of the system. The obtained results show a number of advantages in comparison with many results.

  20. Stripe-to-bubble transition of magnetic domains at the spin reorientation of (Fe/Ni)/Cu/Ni/Cu(001)

    SciTech Connect (OSTI)

    Wu, J.; Choi, J.; Won, C.; Wu, Y. Z.; Scholl, A.; Doran, A.; Hwang, Chanyong; Qiu, Z.

    2010-06-09T23:59:59.000Z

    Magnetic domain evolution at the spin reorientation transition (SRT) of (Fe/Ni)/Cu/Ni/Cu(001) is investigated using photoemission electron microscopy. While the (Fe/Ni) layer exhibits the SRT, the interlayer coupling of the perpendicularly magnetized Ni layer to the (Fe/Ni) layer serves as a virtual perpendicular magnetic field exerted on the (Fe/Ni) layer. We find that the perpendicular virtual magnetic field breaks the up-down symmetry of the (Fe/Ni) stripe domains to induce a net magnetization in the normal direction of the film. Moreover, as the virtual magnetic field increases to exceed a critical field, the stripe domain phase evolves into a bubble domain phase. Although the critical field depends on the Fe film thickness, we show that the area fraction of the minority domain exhibits a universal value that determines the stripe-to-bubble phase transition.

  1. Fast radio-frequency amplitude modulation in multiple-quantum magic-angle-spinning nuclear magnetic resonance: Theory and experiments

    E-Print Network [OSTI]

    Frydman, Lucio

    Fast radio-frequency amplitude modulation in multiple-quantum magic-angle-spinning nuclear magnetic of this experiment has been the poor efficiency of the radio-frequency pulses used in converting multiple-modulated radio-frequency pulses, and which can yield substantial signal and even resolution enhancements over

  2. Low Energy Spin Waves and Magnetic Interactions in SrFe2As2 Dao-Xin Yao,2

    E-Print Network [OSTI]

    Carlson, Erica

    of Sciences, P.O. Box 603, Beijing 100190, China (Received 18 August 2008; published 14 October 2008) We-transition tempera- ture (high-Tc) copper oxides are simple antiferromagnetic (AF) Mott insulators [1] characterized, J1b, and J2 or the microscopic origin of the observed AF spin structure. If magnetism is important

  3. Refreshing One of Several Active Representations: Behavioral and Functional Magnetic Resonance

    E-Print Network [OSTI]

    Johnson, Marcia K.

    Refreshing One of Several Active Representations: Behavioral and Functional Magnetic Resonance with this interpretation, in a functional magnetic resonance imaging study, young adults showed two areas of left they just opened the refrigerator door, telling a story multiple times to the same person, or forgetting

  4. Tunable magnetization dynamics in disordered FePdPt ternary alloys: Effects of spin orbit coupling

    SciTech Connect (OSTI)

    Ma, L.; Fan, W. J., E-mail: stslts@mail.sysu.edu.cn; Chen, F. L.; Zhou, S. M. [Shanghai Key Laboratory of Special Artificial Microstructure and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Li, S. F.; Lai, T. S., E-mail: eleanorfan@163.com [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); He, P. [Department of Physics, Fudan University, Shanghai 200433 (China); Xu, X. G.; Jiang, Y. [State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2014-09-21T23:59:59.000Z

    The magnetization dynamics of disordered Fe?.?(Pd{sub 1–x}Pt{sub x})?.? alloy films was studied by time-resolved magneto-optical Kerr effect and ferromagnetic resonance. The intrinsic Gilbert damping parameter ?? and the resonance linewidth change linearly with the Pt atomic concentration. In particular, the induced in-plane uniaxial anisotropy constant K{sub U} also increases for x increasing from 0 to 1. All these results can be attributed to the tuning effect of the spin orbit coupling. For the disordered ternary alloys, an approach is proposed to control the induced in-plane uniaxial anisotropy, different from conventional thermal treat methods, which is helpful to design and fabrications of spintronic devices.

  5. Electric field controlled reversible magnetic anisotropy switching studied by spin rectification

    SciTech Connect (OSTI)

    Zhou, Hengan; Fan, Xiaolong, E-mail: fanxiaolong@lzu.edu.cn; Wang, Fenglong; Jiang, Changjun; Rao, Jinwei; Zhao, Xiaobing; Xue, Desheng [Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou University, Lanzhou 730000 (China)] [Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Gui, Y. S.; Hu, C.-M. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada)] [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada)

    2014-03-10T23:59:59.000Z

    In this letter, spin rectification was used to study the electric field controlled dynamic magnetic properties of the multiferroic composite which is a Co stripe with induced in-plane anisotropy deposited onto a Pb(Mg{sub 1?3}Nb{sub 2?3})O{sub 3}-PbTiO{sub 3} substrate. Due to the coupling between piezoelectric and magnetoelastic effects, a reversible in-plane anisotropy switching has been realized by varying the history of the applied electric field. This merit results from the electric hysteresis of the polarization in the nonlinear piezoelectric regime, which has been proved by a butterfly type electric field dependence of the in-plane anisotropy field. Moreover, the electric field dependent effective demagnetization field and linewidth have been observed at the same time.

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

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

    a BN sheet. Abstract: In this paper, ab initio method has been employed to study the adsorption energies, electronic structures and magnetic properties of a BN sheet functionalized...

  7. Design and commissioning of a high magnetic field muon spin relaxation spectrometer at the ISIS pulsed neutron and muon source

    SciTech Connect (OSTI)

    Lord, J. S.; McKenzie, I.; Baker, P. J.; Cottrell, S. P.; Giblin, S. R.; Hillier, A. D.; Holsman, B. H.; King, P. J. C.; Nightingale, J. B.; Pratt, F. L.; Rhodes, N. J. [ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX (United Kingdom); Blundell, S. J.; Lancaster, T. [Clarendon Laboratory, Department of Physics, Oxford University, Parks Road, Oxford OX1 3PU (United Kingdom); Good, J.; Mitchell, R.; Owczarkowski, M.; Poli, S. [Cryogenic Limited, 30 Acton Park Industrial Estate, The Vale, Acton, London W3 7QE (United Kingdom); Scheuermann, R. [Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Salman, Z. [ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX (United Kingdom); Clarendon Laboratory, Department of Physics, Oxford University, Parks Road, Oxford OX1 3PU (United Kingdom)

    2011-07-15T23:59:59.000Z

    The high magnetic field (HiFi) muon instrument at the ISIS pulsed neutron and muon source is a state-of-the-art spectrometer designed to provide applied magnetic fields up to 5 T for muon studies of condensed matter and molecular systems. The spectrometer is optimised for time-differential muon spin relaxation studies at a pulsed muon source. We describe the challenges involved in its design and construction, detailing, in particular, the magnet and detector performance. Commissioning experiments have been conducted and the results are presented to demonstrate the scientific capabilities of the new instrument.

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

    E-Print Network [OSTI]

    Woodall, Jerry M.

    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

  9. Size-dependent magnetic ordering and spin-dynamics in DyPO4 and GdPO4 nanoparticles

    SciTech Connect (OSTI)

    Evangelisti, Marco [Instituto de Ciencia de Materiales de Aragon (ICMA), Spain; Sorop, Tibi G [Leiden University; Bakharev, Oleg N [Leiden University; Visser, Dirk [ISIS Facility, Rutherford Appleton Laboratory; Hillier, Adrian D. [ISIS Facility, Rutherford Appleton Laboratory; Alonso, Juan [Universidad de Malaga, Spain; Haase, Markus [University of Osnabruck, Barbarastr Germany; Boatner, Lynn A [ORNL; De Jongh, L. Jos [Leiden University

    2011-01-01T23:59:59.000Z

    Low-temperature magnetic susceptibility and heat capacity measurements on nanoparticles (d 2.6 nm) of the antiferromagnetic compounds DyPO4 (TN = 3:4 K) and GdPO4 (TN = 0:77 K) provide clear demonstrations of finite-size effects, which limit the divergence of the magnetic correlation lengths, thereby suppressing the bulk long-range magnetic ordering transitions. Instead, the incomplete antiferromagnetic order inside the particles leads to the formation of net magnetic moments on the particles. For the nanoparticles of Ising-type DyPO4 superparamagnetic blocking is found in the ac-susceptibility at 1 K, those of the XY-type GdPO4 analogue show a dipolar spin-glass transition at 0:2 K. Monte Carlo simulations for the magnetic heat capacities of both bulk and nanoparticle samples are in agreement with the experimental data. Strong size effects are also apparent in the Dy3+ and Gd3+ spin-dynamics, which were studied by zero-field SR relaxation and high-field 31P-NMR nuclear relaxation measurements. The freezing transitions observed in the ac-susceptibility of the nanoparticles also appear as peaks in the temperature dependence of the zero-field SR rates, but at slightly higher temperatures - as to be expected from the higher frequency of the muon probe. For both bulk and nanoparticles of GdPO4, the muon and 31P-NMR rates are for T 5 K dominated by exchange-narrowed hyperfine broadening arising from the electron spin-spin interactions inside the particles. The dipolar hyperfine interactions acting on the muons and the 31P are, however, much reduced in the nanoparticles. For the DyPO4 analogues the high-temperature rates appear to be fully determined by electron spin-lattice relaxation processes.

  10. A spinning mirror for fast angular scans of EBW emission for magnetic pitch profile measurements

    SciTech Connect (OSTI)

    Volpe, Francesco [Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)

    2010-10-15T23:59:59.000Z

    A tilted spinning mirror rapidly steers the line of sight of the electron Bernstein wave (EBW) emission radiometer at the Mega-Amp Spherical Tokamak (MAST). In order to resist high mechanical stresses at rotation speeds of up to 12 000 rpm and to avoid eddy current induced magnetic braking, the mirror consists of a glass-reinforced nylon substrate of a special self-balanced design, coated with a reflecting layer. By completing an angular scan every 2.5-10 ms, it allows one to characterize with good time resolution the Bernstein-extraordinary-ordinary mode-conversion efficiency as a function of the view angles. Angular maps of conversion efficiency are directly related to the magnetic pitch angle at the cutoff layer for the ordinary mode. Hence, measurements at various frequencies provide the safety factor profile at the plasma edge. Initial measurements and indications of the feasibility of the diagnostic are presented. Moreover, angular scans indicate the best launch conditions for EBW heating.

  11. On the valve nature of a monolayer of aligned molecular magnets in tunneling spin-polarized electrons: Towards organic molecular spintronics

    SciTech Connect (OSTI)

    Chakrabarti, Sudipto; Pal, Amlan J., E-mail: sspajp@iacs.res.in [Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

    2014-01-06T23:59:59.000Z

    We form a monolayer of magnetic organic molecules and immobilize their moments pointing either upwards or downwards with respect to the substrate through an electrostatic-binding process. Such a monolayer is probed with a scanning tunneling microscope tip, which is also magnetized with the magnetization vector pointing towards (or away from) apex of the tip. From spin-polarized tunneling current, we show that the current was higher when magnetization vectors of the tip and molecules were parallel as compared to that when they were anti-parallel. We show that for tunneling of spin-polarized electrons, aligned organic molecular magnets can act as a valve.

  12. Time-domain detection of current controlled magnetization damping in Pt/Ni{sub 81}Fe{sub 19} bilayer and determination of Pt spin Hall angle

    SciTech Connect (OSTI)

    Ganguly, A.; Haldar, A.; Sinha, J.; Barman, A., E-mail: abarman@bose.res.in, E-mail: del.atkinson@durham.ac.uk [Thematic Unit of Excellence on Nanodevice Technology, Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Kolkata 700098 (India); Rowan-Robinson, R. M.; Jaiswal, S.; Hindmarch, A. T.; Atkinson, D. A., E-mail: abarman@bose.res.in, E-mail: del.atkinson@durham.ac.uk [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom)

    2014-09-15T23:59:59.000Z

    The effect of spin torque from the spin Hall effect in Pt/Ni{sub 81}Fe{sub 19} rectangular bilayer film was investigated using time-resolved magneto-optical Kerr microscopy. Current flow through the stack resulted in a linear variation of effective damping up to ±7%, attributed to spin current injection from the Pt into the Ni{sub 81}Fe{sub 19}. The spin Hall angle of Pt was estimated as 0.11?±?0.03. The modulation of the damping depended on the angle between the current and the bias magnetic field. These results demonstrate the importance of optical detection of precessional magnetization dynamics for studying spin transfer torque due to spin Hall effect.

  13. Spin structure and magnetic frustration in multiferroic RMn{sub 2}O{sub 5} (R=Tb,Ho,Dy)

    SciTech Connect (OSTI)

    Blake, G.R. [ISIS Facility, Rutherford Appleton Laboratory-CCLRC, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Chapon, L.C. [ISIS Facility, Rutherford Appleton Laboratory-CCLRC, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Radaelli, P.G. [ISIS Facility, Rutherford Appleton Laboratory-CCLRC, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Park, S.; Hur, N.; Cheong, S-W. [Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Rodriguez-Carvajal, J. [Laboratoire Leon Brillouin (CEA-CNRS), CEA/Saclay, 91191 Gif-sur-Yvette Cedex (France)

    2005-06-01T23:59:59.000Z

    We have studied the crystal and magnetic structures of the magnetoelectric materials RMn{sub 2}O{sub 5} (R=Tb,Ho,Dy) using neutron diffraction as a function of temperature. All three materials display incommensurate antiferromagnetic ordering below 40 K, becoming commensurate on further cooling. For R=Tb,Ho, a commensurate-incommensurate transition takes place at low temperatures. The commensurate magnetic structures have been solved and are discussed in terms of competing exchange interactions. The spin configuration within the ab plane is essentially the same for each system, and the radius of R determines the sign of the magnetic exchange between adjacent planes. The inherent magnetic frustration in these materials is lifted by a small lattice distortion, primarily involving shifts of the Mn{sup 3+} cations and giving rise to a canted antiferroelectric phase.

  14. Magnetism and superconductivity in quark matter

    E-Print Network [OSTI]

    T. Tatsumi; E. Nakano; K. Nawa

    2005-06-01T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Boris V. Gisin

    2014-05-13T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

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

    2014-12-23T23:59:59.000Z

    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.

  17. Study on corrosion behaviors of sintered Nd-Fe-B magnets in different environmental conditions

    SciTech Connect (OSTI)

    Li, J. J.; Li, A. H.; Zhu, M. G.; Pan, W.; Li, W.

    2011-04-01T23:59:59.000Z

    Nd-Fe-B magnets have outstanding magnetic properties, but their corrosion resistance is poor because the rare-earth-rich phases in them are easily oxidized. In this article, we report an investigation of the corrosion behaviors of sintered Nd-Fe-B magnets with varied compositions in different corrosion conditions. The weight losses of the magnets after corrosion testing were measured after brushing off the corrosion products. The magnetic flux losses of the magnets were measured using a fluxmeter. A scanning electron microscope equipped with an energy dispersive x-ray analysis system was employed to observe the corrosion morphology. It was found that the humid-heat resistance of the magnets was obviously improved by partially substituting Dy for Nd and adding minor Co. The corrosion products and morphologies of Nd-Fe-B magnets for the autoclave test were different from those for the constant humid-heat test. The corrosion rates of the magnets for the former were much slower than for the latter; this is probably because the high-pressure steam led to an oxygen-deficient atmosphere, and the liquid film on the surface of the magnet specimens hindered the diffusion of oxygen into the bulk for the autoclave test.

  18. In situ magnetic compensation for potassium spin-exchange relaxation-free magnetometer considering probe beam pumping effect

    SciTech Connect (OSTI)

    Fang, Jiancheng; Wang, Tao, E-mail: wangtaowt@aspe.buaa.edu.cn; Quan, Wei; Yuan, Heng; Li, Yang [School of Instrument Science and Opto-Electronics Engineering, Beihang University, Beijing 100191 (China); Zhang, Hong; Zou, Sheng [School of Instrument Science and Engineering, Southeast University, Nanjing 210096 (China)

    2014-06-15T23:59:59.000Z

    A novel method to compensate the residual magnetic field for an atomic magnetometer consisting of two perpendicular beams of polarizations was demonstrated in this paper. The method can realize magnetic compensation in the case where the pumping rate of the probe beam cannot be ignored. In the experiment, the probe beam is always linearly polarized, whereas, the probe beam contains a residual circular component due to the imperfection of the polarizer, which leads to the pumping effect of the probe beam. A simulation of the probe beam's optical rotation and pumping rate was demonstrated. At the optimized points, the wavelength of the probe beam was optimized to achieve the largest optical rotation. Although, there is a small circular component in the linearly polarized probe beam, the pumping rate of the probe beam was non-negligible at the optimized wavelength which if ignored would lead to inaccuracies in the magnetic field compensation. Therefore, the dynamic equation of spin evolution was solved by considering the pumping effect of the probe beam. Based on the quasi-static solution, a novel magnetic compensation method was proposed, which contains two main steps: (1) the non-pumping compensation and (2) the sequence compensation with a very specific sequence. After these two main steps, a three-axis in situ magnetic compensation was achieved. The compensation method was suitable to design closed-loop spin-exchange relaxation-free magnetometer. By a combination of the magnetic compensation and the optimization, the magnetic field sensitivity was approximately 4 fT/Hz{sup 1/2}, which was mainly dominated by the noise of the magnetic shield.

  19. Spin and orbital Ti magnetism at LaMnO3/SrTiO3 interfaces

    SciTech Connect (OSTI)

    Garcial-Barriocanal, J [Universidad Complutense, Spain; Cezar, J. C. [European Synchrotron Radiation Facility (ESRF); Bruno, F. Y. [Universidad Complutense, Spain; Thakur, P. [European Synchrotron Radiation Facility (ESRF); Brookes, N. B. [European Synchrotron Radiation Facility (ESRF); Utfeld, C. [University of Bristol, UK; Riviera-Calzada, A. [Universidad Complutense, Spain; Giblin, S. R. [ISIS Facility, Rutherford Appleton Laboratory; Taylor, J. W. [ISIS Facility, Rutherford Appleton Laboratory; Duffy, J. A. [University of Warwick, UK; Dugdale, S. B. [University of Bristol, UK; Nakamura, T. [Japan Synchrotron Radiation Research Institute, SPring-8; Kodama, K. [Japan Synchrotron Radiation Research Institute, SPring-8; Leon, C. [Universidad Complutense, Spain; Okamoto, Satoshi [ORNL; Santamaria, J. [Universidad Complutense, Spain

    2010-01-01T23:59:59.000Z

    In systems with strong electron-lattice coupling, such as manganites, orbital degeneracy is lifted, what causes a null expectation value of the orbital moment. Magnetic structure is thus determined by spin-spin superexchange. In titanates, however, with much smaller Jahn-Teller distortions, orbital degeneracy might allow non-zero values of the orbital magnetic moment. Accordingly, novel forms of ferromagnetic superexchange interaction unique to t2g electrons systems have been theoretically predicted, although their experimental observation has remained elusive. Here we report a new kind of Ti3+ ferromagnetism at LaMnO3/SrTiO3 epitaxial interfaces. It results from charge transfer to the empty conduction band of the titanate and has spin and orbital contributions evidencing the role played by orbital degeneracy. The possibility of tuning magnetic alignment (ferromagnetic or antiferromagnetic) of Ti and Mn moments by structural parameters is demonstrated. This result will provide important clues for the understanding of the effects of orbital degeneracy in superexchange coupling.

  20. Anomalous magnetic behavior at the graphene/Co interface

    SciTech Connect (OSTI)

    Mandal, Sumit; Saha, Shyamal K., E-mail: cnssks@iacs.res.in [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

    2014-07-14T23:59:59.000Z

    An intensive theoretical study on the interaction between graphene and transition metal atom has been carried out; however, its experimental verification is still lacking. To explore the theoretical prediction of antiferromagnetic coupling due to charge transfer between graphene and cobalt, epitaxial layer of cobalt is grown on graphene surface. Predicted antiferromagnetic interaction with Neel temperature (T{sub N}???32?K) which anomalously shifts to higher temperature (34?K) and becomes more prominent under application of magnetic field of 1 T is reported. Lowering of magnetoresistance as a consequence of this antiferromagnetic coupling at the interface is also observed.

  1. The critical role of next-nearest-neighbor interlayer interaction in the magnetic behavior of

    E-Print Network [OSTI]

    Choi, Mahn-Soo

    IEC) with contribution from the next-nearest- neighbor (NNN) IEC. This observation reveals that NNN IEC plays a crucial role in the magnetic behavior of these multilayer structures. 5 Author to whom any pronounced when the interlayer exchange coupling (IEC) is AFM [22­25]. It has been established that the AFM

  2. Microstructural Evolution Model of the Sintering Behavior and Magnetic Properties of NiZn Ferrite Nanoparticles

    E-Print Network [OSTI]

    McHenry, Michael E.

    Microstructural Evolution Model of the Sintering Behavior and Magnetic Properties of NiZn Ferrite jlwoods@andrew.cmu.edu, c SCalvin@slc.edu, d jhuth@Spang.co, e mm7g@andrew.cmu.edu Keywords: Ferrite, nanoparticle, sintering, microstructure. Abstract. The sintering of RF plasma synthesized NiZn ferrite

  3. Determining Exchange Splitting in a Magnetic Semiconductor by Spin-Filter Tunneling

    E-Print Network [OSTI]

    Santos, T. S.

    2008-01-01T23:59:59.000Z

    spin- tronic devices. The europium chalcogenides stand outhighly reactive nature of europium, and thus the di?culty indeposition, whereby pure europium metal was evaporated in

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

    SciTech Connect (OSTI)

    Benjamin Michael Meyer

    2003-05-31T23:59:59.000Z

    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?

  5. Conditions for spin-gapless semiconducting behavior in Mn{sub 2}CoAl inverse Heusler compound

    SciTech Connect (OSTI)

    Galanakis, I., E-mail: galanakis@upatras.gr [Department of Materials Science, School of Natural Sciences, University of Patras, GR-26504 Patra (Greece); Özdo?an, K., E-mail: kozdogan@yildiz.edu.tr [Department of Physics, Yildiz Technical University, 34210 ?stanbul (Turkey); ?a??o?lu, E.; Blügel, S. [Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich (Germany)

    2014-03-07T23:59:59.000Z

    Employing ab initio electronic structure calculations, we investigate the conditions for spin-gapless semiconducting (SGS) behavior in the inverse Mn{sub 2}CoAl Heusler compound. We show that tetragonalization of the lattice, which can occur during films growth, keeps the SGS character of the perfect cubic compound. On the contrary, atomic swaps even between sites with different local symmetry destroy the SGS character giving rise to a half-metallic state. Furthermore, the occurrence of Co-surplus leads also to half-metallicity. Thus, we propose that in order to achieve SGS behavior during the growth of Mn{sub 2}CoAl (and similar SGS Heusler compounds) thin films, one should minimize the occurrence of defects, while small deformations of the lattice, due to the lattice mismatch with the substrate, do not play a crucial role.

  6. Level crossings and zero-field splitting in the {Cr8}-cubane spin-cluster studied using inelastic neutron scattering and magnetization

    SciTech Connect (OSTI)

    Vaknin, D. [Ames Laboratory; Garlea, Vasile O [ORNL; Demmel, F. [ISIS Facility, Rutherford Appleton Laboratory; Mamontov, Eugene [ORNL; Nojiri, H [Institute for Materials Research, Tohoku University, Sendai, Japan; Martin, Catalin [Florida State University; Chiorescu, Irinel [Florida State University; Qiu, Y. [National Institute of Standards and Technology (NIST); Luban, M. [Ames Laboratory; Kogerler, P. [Ames Laboratory; Fielden, J. [Ames Laboratory; Engelhardt, L [Francis Marion University, Florence, South Sarolina; Rainey, C [Francis Marion University, Florence, South Sarolina

    2010-01-01T23:59:59.000Z

    Inelastic neutron scattering (INS) in variable magnetic field and high-field magnetization measurements in the millikelvin temperature range were performed to gain insight into the low-energy magnetic excitation spectrum and the field-induced level crossings in the molecular spin cluster {Cr8}-cubane. These complementary techniques provide consistent estimates of the lowest level-crossing field. The overall features of the experimental data are explained using an isotropic Heisenberg model, based on three distinct exchange interactions linking the eight CrIII paramagnetic centers (spins s = 3/2), that is supplemented with a relatively large molecular magnetic anisotropy term for the lowest S = 1 multiplet. It is noted that the existence of the anisotropy is clearly evident from the magnetic field dependence of the excitations in the INS measurements, while the magnetization measurements are not sensitive to its effects.

  7. Modelling current-induced magnetization switching in Heusler alloy Co{sub 2}FeAl-based spin-valve nanopillar

    SciTech Connect (OSTI)

    Huang, H. B. [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Ma, X. Q.; Liu, Z. H.; Zhao, C. P. [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Chen, L. Q. [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2014-04-07T23:59:59.000Z

    We investigated the current-induced magnetization switching in a Heusler alloy Co{sub 2}FeAl-based spin-valve nanopillar by using micromagnetic simulations. We demonstrated that the elimination of the intermediate state is originally resulted from the decease of effective magnetic anisotropy constant. The magnetization switching can be achieved at a small current density of 1.0?×?10{sup 4}?A/cm{sup 2} by increasing the demagnetization factors of x and y axes. Based on our simulation, we found magnetic anisotropy and demagnetization energies have different contributions to the magnetization switching.

  8. Addition and subtraction of spin pumping voltages in magnetic hybrid structures

    SciTech Connect (OSTI)

    Azevedo, A., E-mail: aac@df.ufpe.br; Alves Santos, O.; Cunha, R. O.; Rezende, S. M. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Rodríguez-Suárez, R. [Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago (Chile)

    2014-04-14T23:59:59.000Z

    We report an investigation of the spin pumping voltage generated in bilayers of ferromagnetic/normal metal in which the ferromagnetic layer is yttrium iron garnet or Permalloy and the normal-metal layer is Pt or Ta. We also investigated a special case in which the voltage is detected in single layer of Permalloy under ferromagnetic resonance condition. It is shown that the spin pumping voltage generated in metallic bilayers have contributions from both layers and the resulting voltage depends on the relative signs of charge currents generated by the inverse spin Hall effect. For instance, the spin pumping voltage generated in Ta has the same sign as the one generate in single layer of Permalloy, but contrary to the voltage generated in Pt. When the voltage is measured in shunted metallic bilayers, the resulting voltage can be a sum or a subtraction of the voltages generated in both layers.

  9. Magnetic field dependence of the entanglement entropy of one dimensional spin systems in quantum phase transition induced by a quench

    E-Print Network [OSTI]

    Banasri Basu; Pratul Bandyopadhyay; Priyadarshi Majumdar

    2012-07-10T23:59:59.000Z

    We study the magnetic field dependence of the entanglement entropy in quantum phase transition induced by a quench of the XX, XXX and the LMG model. The entropy for a block of $L$ spins with the rest follows a logarithmic scaling law where the block size $L$ is restricted due to the dependence of the prefactor on the quench time. Within this restricted region the entropy undergoes a renormalization group (RG) flow. From the RG flow equation we have analytically determined the magnetic field dependence of the entropy. The anisotropy parameter dependence of the entropy for the XY and the LMG model has also been studied in this framework. The results are found to be in excellent agreement with that obtained by other authors from numerical studies without any quench.

  10. Putting the Spin on Graphite: Observing the Spins of Impurity...

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

    the Spins of Impurity Atoms Align Friday, February 28, 2014 The existence of magnetism in graphite is a very intriguing subject. The possibility to exploit the magnetic...

  11. 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]

    Boyer, Edmond

    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

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

    E-Print Network [OSTI]

    Agnarsson, Ingi

    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

  13. Multi-bit magnetic memory using Fe8 high spin molecules

    E-Print Network [OSTI]

    Keren, Amit

    16 10 17 10 18 10 19 10 20 QTM Magnetic cores Disk file Magnetic bubble Thin film Optical disk IBM molecule behaves independently. #12;8 [Fe8O2(OH)12(C6H15N3)6]Br7(H2O)Br8H2O Fe8 Molecule Iron Carbon

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

    E-Print Network [OSTI]

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

    2004-09-12T23:59:59.000Z

    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.

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

    DOE Patents [OSTI]

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

    2014-04-08T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  17. Rheological behavior and cryogenic properties of cyanate ester/epoxy insulation material for fusion superconducting magnet

    SciTech Connect (OSTI)

    Wu, Z. X.; Huang, C. J. [Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR (China); Li, L. F. [Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China and State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, C (China); Li, J. W. [Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China and University of Chinese Academy of Sciences, Beijing 100049, PR (China); Tan, R.; Tu, Y. P. [North China Electric Power University, Beijing 102206, PR (China)

    2014-01-27T23:59:59.000Z

    In a Tokamak fusion reactor device like ITER, insulation materials for superconducting magnets are usually fabricated by a vacuum pressure impregnation (VPI) process. Thus these insulation materials must exhibit low viscosity, long working life as well as good radiation resistance. Previous studies have indicated that cyanate ester (CE) blended with epoxy has an excellent resistance against neutron irradiation which is expected to be a candidate insulation material for a fusion magnet. In this work, the rheological behavior of a CE/epoxy (CE/EP) blend containing 40% CE was investigated with non-isothermal and isothermal viscosity experiments. Furthermore, the cryogenic mechanical and electrical properties of the composite were evaluated in terms of interlaminar shear strength and electrical breakdown strength. The results showed that CE/epoxy blend had a very low viscosity and an exceptionally long processing life of about 4 days at 60 °C.

  18. Standing spin-wave mode structure and linewidth in partially disordered hexagonal arrays of perpendicularly magnetized sub-micron Permalloy discs

    SciTech Connect (OSTI)

    Ross, N., E-mail: rossn2282@gmail.com; Kostylev, M., E-mail: mikhail.kostylev@uwa.edu.au [School of Physics, University of Western Australia, Crawley, WA (Australia); Stamps, R. L. [School of Physics, University of Western Australia, Crawley, WA (Australia); SUPA School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2014-09-21T23:59:59.000Z

    Standing spin wave mode frequencies and linewidths in partially disordered perpendicular magnetized arrays of sub-micron Permalloy discs are measured using broadband ferromagnetic resonance and compared to analytical results from a single, isolated disc. The measured mode structure qualitatively reproduces the structure expected from the theory. Fitted demagnetizing parameters decrease with increasing array disorder. The frequency difference between the first and second radial modes is found to be higher in the measured array systems than predicted by theory for an isolated disc. The relative frequencies between successive spin wave modes are unaffected by reduction of the long-range ordering of discs in the array. An increase in standing spin wave resonance linewidth at low applied magnetic fields is observed and grows more severe with increased array disorder.

  19. Magnetic field-assisted manipulation and entanglement of Si spin qubits

    E-Print Network [OSTI]

    M. J. Calderon; Belita Koiller; S. Das Sarma

    2006-08-04T23:59:59.000Z

    Architectures of donor-electron based qubits in silicon near an oxide interface are considered theoretically. We find that the precondition for reliable logic and read-out operations, namely the individual identification of each donor-bound electron near the interface, may be accomplished by fine-tuning electric and magnetic fields, both applied perpendicularly to the interface. We argue that such magnetic fields may also be valuable in controlling two-qubit entanglement via donor electron pairs near the interface.

  20. Magnetic damping and spin polarization of highly ordered B2 Co{sub 2}FeAl thin films

    SciTech Connect (OSTI)

    Cui, Yishen [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Lu, Jiwei, E-mail: jl5tk@virginia.edu [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Schäfer, Sebastian; Khodadadi, Behrouz; Mewes, Tim [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Osofsky, Mike [Naval Research Laboratory, Washington, DC 20375 (United States); Wolf, Stuart A. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)

    2014-08-21T23:59:59.000Z

    Epitaxial Co{sub 2}FeAl films were synthesized using the Biased Target Ion Beam Deposition technique. Post annealing yielded Co{sub 2}FeAl films with an improved B2 chemical ordering. Both the magnetization and the Gilbert damping parameter were reduced with increased B2 ordering. A low damping parameter, ?0.002, was attained in B2 ordered Co{sub 2}FeAl films without the presence of the L2{sub 1} Heusler phase, which suggests that the B2 structure is sufficient for providing low damping in Co{sub 2}FeAl. The spin polarization was ?53% and was insensitive to the chemical ordering.

  1. Finite temperature spin-dynamics and phase transitions in spin-orbital models

    SciTech Connect (OSTI)

    Chen, C.-C.

    2010-04-29T23:59:59.000Z

    We study finite temperature properties of a generic spin-orbital model relevant to transition metal compounds, having coupled quantum Heisenberg-spin and Ising-orbital degrees of freedom. The model system undergoes a phase transition, consistent with that of a 2D Ising model, to an orbitally ordered state at a temperature set by short-range magnetic order. At low temperatures the orbital degrees of freedom freeze-out and the model maps onto a quantum Heisenberg model. The onset of orbital excitations causes a rapid scrambling of the spin spectral weight away from coherent spin-waves, which leads to a sharp increase in uniform magnetic susceptibility just below the phase transition, reminiscent of the observed behavior in the Fe-pnictide materials.

  2. Magnetic resonance visualization of conductive structures by sequence-triggered direct currents and spin-echo phase imaging

    SciTech Connect (OSTI)

    Eibofner, Frank; Wojtczyk, Hanne; Graf, Hansjörg, E-mail: hansjoerg.graf@med.uni-tuebingen.de, E-mail: drGraf@t-online.de [Section on Experimental Radiology, University Hospital Tübingen, Tübingen D-72076 (Germany)] [Section on Experimental Radiology, University Hospital Tübingen, Tübingen D-72076 (Germany); Clasen, Stephan [Department of Diagnostic and Interventional Radiology, University Hospital Tübingen, Tübingen D-72076 (Germany)] [Department of Diagnostic and Interventional Radiology, University Hospital Tübingen, Tübingen D-72076 (Germany)

    2014-06-15T23:59:59.000Z

    Purpose: Instrument visualization in interventional magnetic resonance imaging (MRI) is commonly performed via susceptibility artifacts. Unfortunately, this approach suffers from limited conspicuity in inhomogeneous tissue and disturbed spatial encoding. Also, susceptibility artifacts are controllable only by sequence parameters. This work presents the basics of a new visualization method overcoming such problems by applying sequence-triggered direct current (DC) pulses in spin-echo (SE) imaging. SE phase images allow for background free current path localization. Methods: Application of a sequence-triggered DC pulse in SE imaging, e.g., during a time period between radiofrequency excitation and refocusing, results in transient field inhomogeneities. Dependent on the additional z-magnetic field from the DC, a phase offset results despite the refocusing pulse. False spatial encoding is avoided by DC application during periods when read-out or slice-encoding gradients are inactive. A water phantom containing a brass conductor (water equivalent susceptibility) and a titanium needle (serving as susceptibility source) was used to demonstrate the feasibility. Artifact dependence on current strength and orientation was examined. Results: Without DC, the brass conductor was only visible due to its water displacement. The titanium needle showed typical susceptibility artifacts. Applying triggered DC pulses, the phase offset of spins near the conductor appeared. Because SE phase images are homogenous also in regions of persistent field inhomogeneities, the position of the conductor could be determined with high reliability. Artifact characteristic could be easily controlled by amperage leaving sequence parameters unchanged. For an angle of 30° between current and static field visualization was still possible. Conclusions: SE phase images display the position of a conductor carrying pulsed DC free from artifacts caused by persistent field inhomogeneities. Magnitude and phase images are acquired simultaneously under the same conditions without the use of extra measurement time. The presented technique offers many advantages for precise instrument localization in interventional MRI.

  3. Electron spin resonance and magnetic characterization of the Gd{sub 5.09}Ge{sub 2.03}Si{sub 1.88}

    SciTech Connect (OSTI)

    Pires, M.J.M.; Carvalho, A. Magnus G.; Gama, S.; Silva, E.C. da; Coelho, A.A.; Mansanares, A.M. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, Unicamp, Cx. P. 6165, 13083-970, Campinas, Sao Paulo (Brazil)

    2005-12-01T23:59:59.000Z

    Electron spin resonance was applied on samples of Gd{sub 5.09}Ge{sub 2.03}Si{sub 1.88}. The results are discussed under the scope of magnetization measurements, optical metallography, and wavelength dispersive spectroscopy. Polycrystalline arc-melted samples submitted to different heat treatments were investigated. The correlation of the electron spin resonance and magnetization results permitted a characterization of the present phases and their transitions. Two coexisting phases in the temperature range between two phase transitions have been identified and associated to distinct crystallographic phases. Additionally, the magnetic moment at high temperatures has been estimated from the measured effective g factor. A peak value of 21.5 J/kg K for the magnetocaloric effect was obtained for a sample heat treated at 1500 deg. C for 16 h.

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

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

    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

    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.

  5. Resonant normal form and asymptotic normal form behavior in magnetic bottle Hamiltonians

    E-Print Network [OSTI]

    C. Efthymiopoulos; M. Harsoula; G. Contopoulos

    2015-01-28T23:59:59.000Z

    We consider normal forms in `magnetic bottle' type Hamiltonians of the form $H=\\frac{1}{2}(\\rho^2_\\rho+\\omega^2_1\\rho^2) +\\frac{1}{2}p^2_z+hot$ (second frequency $\\omega_2$ equal to zero in the lowest order). Our main results are: i) a novel method to construct the normal form in cases of resonance, and ii) a study of the asymptotic behavior of both the non-resonant and the resonant series. We find that, if we truncate the normal form series at order $r$, the series remainder in both constructions decreases with increasing $r$ down to a minimum, and then it increases with $r$. The computed minimum remainder turns to be exponentially small in $\\frac{1}{\\Delta E}$, where $\\Delta E$ is the mirror oscillation energy, while the optimal order scales as an inverse power of $\\Delta E$. We estimate numerically the exponents associated with the optimal order and the remainder's exponential asymptotic behavior. In the resonant case, our novel method allows to compute a `quasi-integral' (i.e. truncated formal integral) valid both for each particular resonance as well as away from all resonances. We applied these results to a specific magnetic bottle Hamiltonian. The non resonant normal form yields theorerical invariant curves on a surface of section which fit well the empirical curves away from resonances. On the other hand the resonant normal form fits very well both the invariant curves inside the islands of a particular resonance as well as the non-resonant invariant curves. Finally, we discuss how normal forms allow to compute a critical threshold for the onset of global chaos in the magnetic bottle.

  6. Magnetization switching in 70-nm-wide pseudo-spin-valve nanoelements Xiaobin Zhua)

    E-Print Network [OSTI]

    Grütter, Peter

    Fe, respectively, in this case separated by a spacer layer. The individual elements have dimensions of 70 nm 550 nm with submicron or deep- submicron dimensions.4,5 These PSV or MTJ elements con- sist of asymmetric sandwiches is magnetically hard. For elements with micron-scale dimensions, interactions between the layers can lead

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

    SciTech Connect (OSTI)

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

    2014-06-21T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    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

    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.

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

    E-Print Network [OSTI]

    Kortright, Jeffrey B

    2008-01-01T23:59:59.000Z

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

  10. A New Spin on Photoemission Spectroscopy

    SciTech Connect (OSTI)

    Advanced Light Source; Jozwiak, Chris

    2008-12-18T23:59:59.000Z

    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.

  11. Spin current evolution in the separated spin-up and spin-down quantum hydrodynamics

    E-Print Network [OSTI]

    Trukhanova, Mariya Iv

    2015-01-01T23:59:59.000Z

    We have developed the quantum hydrodynamic model that describes particles with spin-up and with spin-down in separate. We have derived the equation of the spin current evolution as a part of the set of the quantum hydrodynamics (QHD) equations that treat particles with different projection of spin on the preferable direction as two different species. We have studied orthogonal propagation of waves in the external magnetic field and determined the contribution of quantum corrections due to the Bohm potential and to magnetization energy of particles with different projections of spin in the spin current wave dispersion. We have analyzed the limits of weak and strong magnetic fields.

  12. 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)

    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

    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}.

  13. Macrospin modeling of sub-ns pulse switching of perpendicularly magnetized free layer via spin-orbit torques for cryogenic memory applications

    SciTech Connect (OSTI)

    Park, Junbo; Rowlands, G. E.; Lee, O. J.; Buhrman, R. A. [Cornell University, Ithaca, New York 14853 (United States); Ralph, D. C. [Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell, Ithaca, New York 14853 (United States)

    2014-09-08T23:59:59.000Z

    We model, using the macrospin approximation, the magnetic reversal of a perpendicularly magnetized nanostructured free layer formed on a normal, heavy-metal nanostrip, subjected to spin-orbit torques (SOTs) generated by short (?0.5?ns) current pulses applied to the nanostrip, to examine the potential for SOT-based fast, efficient cryogenic memory. Due to thermal fluctuations, if solely an anti-damping torque is applied, then, for a device with sufficiently low anisotropy (H{sub anis}{sup 0}???1 kOe) suitable for application in cryogenic memory, a high magnetic damping parameter (??0.1?0.2) is required for reliable switching over a significant variation of pulse current. The additional presence of a substantial field-like torque improves switching reliability even for low damping (??0.03).

  14. Superconducting Magnet Division

    E-Print Network [OSTI]

    Superconducting Magnet Division DOE NP Program Review - July 06 1 Brookhaven Magnet Division - Nuclear Physics Program Support Activities Superconducting Magnet Program RHIC Operations Support Spin Summary Peter Wanderer, DOE review, July 25, 2006 Acting Head, Superconducting Magnet Division #12

  15. Numerical Simulation of Plasma Behavior in a Magnetic Nozzle of a Laser-plasma Driven Nuclear Electric Propulsion System

    SciTech Connect (OSTI)

    Kajimura, Y. [Research Institute for Sustainable Humanosphere (RISH), Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Japan Science and Technology Agency (JST), CREST 4-1-8 Hon-chou, Kawaguchi, Saitama 332-0012 (Japan); Matsuda, N.; Hayashida, K.; Maeno, A.; Nakashima, H. [Department of Advanced Energy Engineering Science, Interdisciplinary Graduate school of Engineering Sciences, Kyushu University, Kasugakouen 6-1, Kasuga, Fukuoka 816-580 (Japan)

    2008-12-31T23:59:59.000Z

    Numerical simulations of plasma behavior in a magnetic nozzle of a Laser-Plasma Driven Nuclear Electric Propulsion System are conducted. The propellant is heated and accelerated by the laser and expanded isotropically. The magnetic nozzle is a combination of solenoidal coils and used to collimate and guide the plasma to produce thrust. Simulation calculations by a three-dimensional hybrid code are conducted to examine the plasma behaviors in the nozzle and to estimate the thrust efficiency. We also estimate a fraction ({alpha}) of plasma particles leaking in the forward (spacecraft) direction. By a combination of a few coils, we could decrease {alpha} value without degrading the thrust efficiency. Finally, the shaped propellant is proposed to increase the thrust efficiency.

  16. Spin - or, actually: Spin and Quantum Statistics

    E-Print Network [OSTI]

    Juerg Froehlich

    2008-02-29T23:59:59.000Z

    The history of the discovery of electron spin and the Pauli principle and the mathematics of spin and quantum statistics are reviewed. Pauli's theory of the spinning electron and some of its many applications in mathematics and physics are considered in more detail. The role of the fact that the tree-level gyromagnetic factor of the electron has the value g = 2 in an analysis of stability (and instability) of matter in arbitrary external magnetic fields is highlighted. Radiative corrections and precision measurements of g are reviewed. The general connection between spin and statistics, the CPT theorem and the theory of braid statistics are described.

  17. Contributions of the electronic spin and orbital current to the CoCl{sub 4}{sup 2-} magnetic field probed in polarised neutron diffraction experiments

    SciTech Connect (OSTI)

    Cassam-Chenaie, Patrick [Laboratoire J. A. Dieudonne, UMR 6621 du CNRS, Faculte des Sciences, Parc Valrose, 06108 Nice cedex 2 (France); Jayatilaka, Dylan [School of Chemistry and Biochemistry, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia)

    2012-08-14T23:59:59.000Z

    Polarised neutron diffraction experiments conducted at 4.2 K on Cs{sub 3}CoCl{sub 5} crystals have been analysed by using a four-dimensional model Hilbert space made of ab initio n-electron wave functions of the CoCl{sub 4}{sup 2-} molecular ion. Two spin-orbit mixing coefficients and several configuration interaction coefficients have been optimized by fitting calculated magnetic structure factors to experimental ones, to obtain the best ensemble density operator that is representable in the model space. A goodness of fit, {chi}{sup 2}, less then 1 has been obtained for the first time for the two experimental data sets available. In the present article, the optimized density operators are used to calculate the magnetic field densities that are the genuine observables probed in neutron diffraction experiments. Density maps of such observables are presented for the first time and numerical details are provided. The respective contributions of spin density and orbital current to the magnetic field density are analyzed.

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

    SciTech Connect (OSTI)

    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

    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.

  19. A nuclear magnetic resonance probe of Fe-Al and Al20V2Eu intermetallics 

    E-Print Network [OSTI]

    Chi, Ji

    2009-05-15T23:59:59.000Z

    and electronic properties. There has been more and more interest in intermetallic compounds containing rare-earth and transition metals, in cases of weak magnetic behavior resulting in variety of characteristics including spin and valence fluctuations, spin... and charge orderings, heavy Fermion behavior and Kondo insulators. Kondo insulators are 3d, 4f and 5f intermetallic compounds. At high temperatures, they behave like metals. But as temperature is reduced, an energy gap opens in the conduction band...

  20. Magnetic force microscopy and x-ray scattering study of 70550 nm2 pseudo-spin-valve nanomagnets

    E-Print Network [OSTI]

    Grütter, Peter

    The magnetic properties of lithographically defined mul- tilayered magnetic solids with three dimensions reversal is affected by the shape and reduced dimensions of these nanomagnets are of considerable interest or metallic spacer. Future high-density MRAM devices will require layered magnetic elements with thicknesses

  1. Proposal for high-speed and high-fidelity electron-spin initialization in a negatively charged quantum dot coupled to a microcavity in a weak external magnetic field

    SciTech Connect (OSTI)

    Majumdar, Arka; Lin Ziliang; Faraon, Andrei; Vuckovic, Jelena [E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305 (United States)

    2010-08-15T23:59:59.000Z

    We describe a proposal for fast electron-spin initialization in a negatively charged quantum dot coupled to a microcavity without the need for a strong magnetic field. We employ two-photon excitation to access trion states that are spin forbidden by one-photon excitation. Our simulation shows a maximum initialization speed of 1.3 GHz and maximum fidelity of 99.7% with realistic system parameters.

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

    E-Print Network [OSTI]

    Brune, Harald

    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

  3. Spin-current-induced dynamics in ferromagnetic nanopillars of lateral spin-valve structures

    E-Print Network [OSTI]

    Otani, Yoshichika

    Spin-current-induced dynamics in ferromagnetic nanopillars of lateral spin-valve structures J 4 February 2009 Under electrical injection, spin accumulation occurs in lateral spin valves in a lateral spin valve while simultaneously sweeping an external magnetic field. We observe changes

  4. Magnetic behavior of monoatomic Co wires on Pd,,110... R. Robles, J. Izquierdo, and A. Vega

    E-Print Network [OSTI]

    Rodriguez, Roberto

    The development of magnetic devices constitutes one of the most important tasks in high technology. The magnetic storage industry continues with plans of increasing growing rate in areal storage density. In addition of supported nanostructures. This opens the possibil- ity, as discussed before, of the development of extremely

  5. 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]

    V. G. Baryshevsky; A. A. Gurinovich

    2005-06-14T23:59:59.000Z

    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.

  6. Breakdown by magnetic field in a La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/MgO/Fe spin valve

    SciTech Connect (OSTI)

    Wu Xiaojie; Meng Jian [State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022 (China); Zhang Zhenzhong [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Dongnanhu Road, Changchun 130033 (China)

    2012-03-19T23:59:59.000Z

    A La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/MgO/Fe spin valve with inverse tunneling magnetoresistance (TMR) was fabricated on a (100) SrTiO{sub 3} substrate by radio frequency magnetron sputtering. Giant TMR ratios up to 540% were obtained. The breakdown of the spin valve was observed at high magnetic field, which was attributed to the joint action of the invalidation of MgO barrier and the shift of Fermi energy in La{sub 0.7}Sr{sub 0.3}MnO{sub 3} at high magnetic field.

  7. Effectiveness of classical spin simulations for describing NMR relaxation of quantum spins

    E-Print Network [OSTI]

    Tarek A. Elsayed; Boris V. Fine

    2014-09-29T23:59:59.000Z

    We investigate the limits of effectiveness of classical spin simulations for predicting free induction decays (FIDs) measured by solid-state nuclear magnetic resonance (NMR) on systems of quantum nuclear spins. The specific limits considered are associated with the range of interaction, the size of individual quantum spins and the long-time behavior of the FID signals. We compare FIDs measured or computed for lattices of quantum spins (mainly spins 1/2) with the FIDs computed for the corresponding lattices of classical spins. Several cases of excellent quantitative agreement between quantum and classical FIDs are reported along with the cases of gradually decreasing quality of the agreement. We formulate semi-empirical criteria defining the situations, when classical simulations are expected to accurately reproduce quantum FIDs. Our findings indicate that classical simulations may be a quantitatively accurate tool of first principles calculations for a broad class of macroscopic systems, where individual quantum microscopic degrees of freedom are far from the classical limit.

  8. Spin-Orbit Torque Driven Magnetization Dynamics in (Ga,Mn)As and (Ga,Mn)(As,P) Dilute Magnetic Semiconductors

    E-Print Network [OSTI]

    Vehstedt, Erin Kathleen

    2014-07-18T23:59:59.000Z

    Spintronics-based technologies are poised to leapfrog the current limitations on the scaling, speed, and power consumption of electronic devices. Conventional devices rely on complex structures and magnetic-field-based switching to manipulate data...

  9. Coherent spin mixing dynamics in thermal $^{87}$Rb spin-1 and spin-2 gases

    E-Print Network [OSTI]

    He, Xiaodong; Li, Xiaoke; Wang, Fudong; Xu, Zhifang; Wang, Dajun

    2015-01-01T23:59:59.000Z

    We study the non-equilibrium coherent spin mixing dynamics in ferromagnetic spin-1 and antiferromagnetic spin-2 thermal gases of ultracold $^{87}$Rb atoms. Long lasting spin population oscillations with magnetic field dependent resonances are observed in both cases. Our observations are well reproduced by Boltzmann equations of the Wigner distribution function. Compared to the equation of motion of spinor Bose-Einstein condensates, the only difference here is a factor of two increase in the spin-dependent interaction, which is confirmed directly in the spin-2 case by measuring the relation between the oscillation amplitude and the sample's density.

  10. Magnetic behavior of LaMn{sub 2}(Si{sub (1?x)}Ge{sub x}){sub 2} compounds characterized by magnetic hyperfine field measurements

    SciTech Connect (OSTI)

    Bosch-Santos, B., E-mail: brianna@usp.br; Carbonari, A. W.; Cabrera-Pasca, G. A.; Saxena, R. N. [Instituto de Pesquisas Energéticas e Nucleares, University of São Paulo, 05508-000 São Paulo (Brazil)

    2014-05-07T23:59:59.000Z

    The temperature dependence of the magnetic hyperfine field (B{sub hf}) at Mn atom sites was measured in LaMn{sub 2}(Si{sub (1?x)}Ge{sub x}){sub 2}, with 0???x???1, compounds with perturbed ??? angular correlation spectroscopy using {sup 111}In({sup 111}Cd) as probe nuclei in the temperature range from 20?K to 480?K. The results show a transition from antiferromagnetic to ferromagnetic ordering for all studied compounds when Ge gradually replaces Si and allowed an accurate determination of the Néel temperature (T{sub N}) for each compound. It was observed that T{sub N} decreases when Ge concentration increases. Conversely, the Curie temperature increases with increase of Ge concentration. This remarkable change in the behavior of the transition temperatures is discussed in terms of the Mn-Mn distance and ascribed to a change in the exchange constant J{sub ex}.

  11. Evidence of exchange bias effect originating from the interaction between antiferromagnetic core and spin glass shell

    SciTech Connect (OSTI)

    Zhang, X. K., E-mail: zhangxianke77@163.com; Yuan, J. J.; Yu, H. J.; Zhu, X. R.; Xie, Y. M. [School of Physics and Electronics, Institute of Optoelectronic Materials and Technology, Gannan Normal University, Ganzhou 341000 (China); Tang, S. L.; Xu, L. Q. [Nanjing National Laboratory of Microstructures, College of Physics, Nanjing University, Nanjing 210093 (China)

    2014-07-14T23:59:59.000Z

    Spin glass behavior and exchange bias effect have been observed in antiferromagnetic SrMn{sub 3}O{sub 6?x} nanoribbons synthesized via a self-sacrificing template process. The magnetic field dependence of thermoremanent magnetization and isothermal remanent magnetization shows that the sample is good correspondence to spin glass and diluted antiferromagnetic system for the applied field H??2?T, respectively. By detailed analysis of training effect using Binek's model, we argue that the observed exchange bias effect in SrMn{sub 3}O{sub 6?x} nanoribbons arises entirely from an interface exchange coupling between the antiferromagnetic core and spin glass shell. The present study is useful for understanding the nature of shell layer and the origin of exchange bias effect in other antiferromagnetic nanosystems as well.

  12. Coexistence of considerable inter-particle interactions and spin-glass behavior in La{sub 0.7}Ca{sub 0.3}MnO{sub 3} nanoparticles

    SciTech Connect (OSTI)

    Thanh, T. D., E-mail: thanhxraylab@yahoo.com [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Institute of Materials Science, VAST, 18-Hoang Quoc Viet, Hanoi (Viet Nam); Manh, D. H.; Phuc, N. X. [Institute of Materials Science, VAST, 18-Hoang Quoc Viet, Hanoi (Viet Nam); Phan, T. L.; Yu, S. C., E-mail: scyu@chungbuk.ac.kr [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Phong, P. T. [Nha Trang Pedagogic College, 1 Nguyen Chanh Street, Nha Trang (Viet Nam); Hung, L. T. [Department of Physics, University of Vinh, Nghe An (Viet Nam)

    2014-05-07T23:59:59.000Z

    We have studied the magnetic and spin-glass (SG) properties of La{sub 0.7}Ca{sub 0.3}MnO{sub 3} single-crystalline nanoparticles, which were prepared by the mechanical milling method with different milling times (t{sub m}). Analyzing the susceptibility data in the paramagnetic region indicates both ferromagnetic (FM) and anti-FM interactions coexisting in nanoparticles. Additionally, there is a peak associated with the freezing temperature (T{sub f}) appearing on the real part curve of the ac susceptibility, ??(T). The T{sub f} value increases with increasing frequency as expected for SG systems. The SG behavior was also checked by using the criterion parameter c?=??T{sub f}/T{sub f}?(log{sub 10}f), and the power law ??=??{sub 0}(T/T{sub g} ? 1){sup ?z?}. The obtained values of c???5?×?10{sup ?2}, ?{sub 0} ? 10{sup ?5} s and z? ? 2–3 are consistent with those expected for SG-like systems, suggesting an existence of a SG phase transition at T{sub g} below T{sub f}, which decreases with decreasing ?D?. Basing on ln(f) versus T{sub f} data, and the Néel-Arrhenius model [ln(f)?=?ln(f{sub 0}) - E{sub a}/k{sub B}T] and Vogel–Fulcher law [ln(f)?=?ln(f{sub 0}) - E{sub a}/k{sub B}(T - T{sub 0})], the Larmor frequency (f{sub 0}), activation energy (E{sub a}) and effective temperature (T{sub 0}) for the samples with different ?D? were determined. Obtained results indicate the existence a strong interaction between nanoparticles.

  13. Separated spin-up and spin-down quantum hydrodynamics of degenerated electrons: spin-electron acoustic wave appearance

    E-Print Network [OSTI]

    Pavel A. Andreev

    2014-05-04T23:59:59.000Z

    Quantum hydrodynamic (QHD) model of charged spin-1/2 particles contains physical quantities defined for all particles of a species including particles with spin-up and with spin-down. Different population of states with different spin direction is included in the spin density (magnetization). In this paper we derive a QHD model, which separately describes spin-up electrons and spin-down electrons. Hence we consider electrons with different projection of spin on the preferable direction as two different species of particles. We show that numbers of particles with different spin direction do not conserve. Hence the continuity equations contain sources of particles. These sources are caused by the interactions of spins with magnetic field. Terms of similar nature arise in the Euler equation. We have that z-projection of the spin density is no longer an independent variable. It is proportional to difference between concentrations of electrons with spin-up and electrons with spin-down. In terms of new model we consider propagation of waves in magnetized plasmas of degenerate electrons and motionless ions. We show that new form of QHD equations gives all solutions obtained from traditional form of QHD equations with no distinguish of spin-up and spin-down states. But it also reveals a sound-like solution we call the spin-electron acoustic wave. Coincidence of most solutions is expected since we started derivation with the same basic equation.

  14. Neutrino magnetic moment in a magnetized plasma

    E-Print Network [OSTI]

    N. V. Mikheev; E. N. Narynskaya

    2010-11-08T23:59:59.000Z

    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.

  15. Tuning magnetotransport in PdPt/Y{sub 3}Fe{sub 5}O{sub 12}: Effects of magnetic proximity and spin-orbit coupling

    SciTech Connect (OSTI)

    Zhou, X.; Ma, L.; Shi, Z.; Zhou, S. M., E-mail: shiming@tongji.edu.cn [Shanghai Key Laboratory of Special Artificial Microstructure and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Guo, G. Y., E-mail: gyguo@phys.ntu.edu.tw [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Hu, J.; Wu, R. Q. [Department of Physics and Astronomy, University of California, Irvine, California 92697-4575 (United States)

    2014-07-07T23:59:59.000Z

    We report that anisotropic magnetoresistance (AMR) and anomalous Hall conductivity (AHC) in the Pd{sub 1?x}Pt{sub x}/Y{sub 3}Fe{sub 5}O{sub 12} (YIG) bilayers could be tuned by varying the Pt concentration (x) and also temperature (T). In particular, the AHC at low T changes its sign when x increases from 0 to 1, agreeing with the negative and positive AHC predicted by our ab initio calculations for the magnetic proximity (MP)-induced ferromagnetic Pd and Pt, respectively. The AMR ratio is enhanced by ten times when x increases from 0 to 1. Furthermore, the AMR of PdPt/YIG bilayers shows similar T-dependence as the magnetic susceptibility of the corresponding bulk Pd/Pt, also indicating the MP effect as the origin of the AMR. The present work demonstrates that the alloying of Pt and Pd not only offers tunable spin-orbit coupling but also is useful to reveal the nature of the AMR and AHC in Pt/YIG bilayers, which are useful for spintronics applications.

  16. Microscopic structure and magnetic behavior of arrays of electrodeposited Ni and Fe nanowires

    SciTech Connect (OSTI)

    Xu, X.; Zangari, G. [Department of Chemical Engineering, University of Virginia, 102 Engineer's Way, Charlottesville, Virginia 22904 (United States); Department of Materials Science and Engineering, University of Virginia, 116 Engineer's Way, Charlottesville, Virginia 22904 (United States)

    2005-05-15T23:59:59.000Z

    Arrays of Ni and Fe nanowires with length up to 6 {mu}m were fabricated by voltage controlled electrodeposition within track etched polycarbonate membranes with nominal pore diameter 50 nm, using dc or pulsed voltage. Magnetostatic interactions between wires are found to be important in determining magnetic properties and switching processes. Ni arrays switch by quasicoherent rotation when the magnetic field is applied near to the average wire axis, and by curling at large angles. The importance of curling processes increases with wire length, due to the larger demagnetizing field. The properties of Fe wires are dominated by magnetostatic interactions; these arrays switch by curling and no definite easy axis is observed in pulse-plated, amorphous wires.

  17. 30 CHAPTER 2. ABSTRACTS by tracking individual magnetic elements. The analysis reveals a strong spin down near the pole, which

    E-Print Network [OSTI]

    Ng, Chung-Sang

    . SWAP will image the solar corona in a 17.5nm bandpass at a 1 min cadence. SWAP is dedicated to track30 CHAPTER 2. ABSTRACTS by tracking individual magnetic elements. The analysis reveals a strong PROBA2 is an ESA microsatellite scheduled for launch in May 2008. Its scientific payload includes solar

  18. Cooperative spin freezing and the pinning assisted thermoremanent magnetization in Ni{sub 2.04}Mn{sub 1.36}Sn{sub 0.6} alloy

    SciTech Connect (OSTI)

    Pramanick, S.; Chattopadhyay, S.; Giri, S.; Majumdar, S., E-mail: sspsm2@iacs.res.in [Department of Solid State Physics, Indian Association for the Cultivation of Science, 2A and B Raja S. C. Mullick Road, Jadavpur, Kolkata 700 032 (India); Chatterjee, S. [UGC-DAE Consortium for Scientific Research, Kolkata Centre, Sector III, LB-8, Salt Lake, Kolkata 700 098 (India)

    2014-08-28T23:59:59.000Z

    Detailed investigation on the ground-state magnetic properties of Ni{sub 2.04}Mn{sub 1.36}Sn{sub 0.6} alloy is reported. The sample undergoes martensitic type structural transformation from a cubic austenite phase to an orthorhombic martensite phase on cooling around T{sub M}?=?220?K. It orders ferromagnetically just above room temperature with T{sub C}?=?310?K. The phases above and below T{sub M} are predominantly ferromagnetic, although incipient antiferromagnetic correlations have been mooted between the Mn atoms sitting at two different crystallographic sites. The zero-field-cooled magnetic state shows a step like anomaly around T{sub B}?=?100?K, and the sample is found to show clear signature of spin glass like behaviour below this point. It is also associated with considerable exchange bias effect below T{sub B}, where horizontal shift of isothermal magnetization loop is observed in the field-cooled state. Apart from exchange bias, there exists large thermoremanent magnetization. Interestingly, the thermoremanent magnetization obtained by cooling the sample from above and just below the first order martensitic transition failed to show any sizable change, which rules out any major role of field induced arrest across the first order transition. The observed thermoremanent magnetization is presumably due to the effect of pinning of uncompensated spins in this magnetically inhomogeneous system with random ferromagnetic as well as antiferromagnetic bonds on field cooling through the onset point (T{sub B}) of the spin-glass like state.

  19. Spin-dependent transport in a nanopillar non-local spin valve J.-B. Laloe a,, T. Yang a

    E-Print Network [OSTI]

    Otani, Yoshichika

    Spin-dependent transport in a nanopillar non-local spin valve J.-B. Lalo¨e a,Ã, T. Yang a , T: Lateral spin-valve Spin current a b s t r a c t We investigate the injection of a pure spin current into a non-magnetic Cu wire in a lateral spin valve. We detect the spin accumulation occurring

  20. Neutron diffraction study of magnetic field induced behavior in the heavy Fermion Ce3Co4Sn13

    SciTech Connect (OSTI)

    Christianson, Andrew D [ORNL; Goremychkin, E. A. [ISIS Facility, Rutherford Appleton Laboratory; Gardner, J. S. [Indiana University; Kang, H. J. [National Institute of Standards and Technology (NIST); Chung, J.-H. [National Institute of Standards and Technology (NIST); Manuel, P. [ISIS Facility, Rutherford Appleton Laboratory; Thompson, J. D. [Los Alamos National Laboratory (LANL); Sarrao, J. L. [Los Alamos National Laboratory (LANL); Lawrence, J. M. [University of California, Irvine

    2008-01-01T23:59:59.000Z

    The specific heat of Ce3Co4Sn13 exhibits a crossover from heavy Fermion behavior with antiferromagnetic correlations at low field to single impurity Kondo behavior above 2 T. We have performed neutron diffraction measurements in magnetic fields up to 6 Tesla on single crystal samples. The (001) position shows a dramatic increase in intensity in field which appears to arise from static polarization of the 4f level and which at 0.14 K also exhibits an anomaly near 2T reflecting the crossover to single impurity behavior.

  1. Effect of electronic reconstruction on cuprate-manganite spin switches.

    SciTech Connect (OSTI)

    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

    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.

  2. Localizable entanglement in antiferromagnetic spin chains

    SciTech Connect (OSTI)

    Jin, B.-Q.; Korepin, V.E. [C.N. Yang Institute for Theoretical Physics, State University of New York at Stony Brook, Stony Brook, New York 11794-3840 (United States)

    2004-06-01T23:59:59.000Z

    Antiferromagnetic spin chains play an important role in condensed matter and statistical mechanics. Recently XXX spin chain was discussed in relation to information theory. Here we consider localizable entanglement. It is how much entanglement can be localized on two spins by performing local measurements on other individual spins (in a system of many interacting spins). We consider the ground state of antiferromagnetic spin chain. We study localizable entanglement [represented by concurrence] between two spins. It is a function of the distance. We start with isotropic spin chain. Then we study effects of anisotropy and magnetic field. We conclude that anisotropy increases the localizable entanglement. We discovered high sensitivity to a magnetic field in cases of high symmetry. We also evaluated concurrence of these two spins before the measurement to illustrate that the measurement raises the concurrence.

  3. 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]

    Harris, Thomas

    2010-01-01T23:59:59.000Z

    computing, and magnetic refrigeration. 6-9 However, in ordercomputing, and magnetic refrigeration. 3 However, in order

  4. Spin rotation and depolarization of high-energy particles in crystals at Hadron Collider (LHC) and Future Circular Collider (FCC) energies and the possibility to measure the anomalous magnetic moments of short-lived particles

    E-Print Network [OSTI]

    Baryshevsky, V G

    2015-01-01T23:59:59.000Z

    We study the phenomena of spin rotation and depolarization of high-energy particles in crystals in the range of high energies that will be available at Hadron Collider (LHC) and Future Circular Collider (FCC). It is shown that these phenomena can be used to measure the anomalous magnetic moments of short-lived particles in this range of energies. We also demonstrate that the phenomenon of particle spin depolarization in crystals provides a unique possibility of measuring the anomalous magnetic moment of negatively-charged particles (e.g., beauty baryons), for which the channeling effect is hampered due to far more rapid dechanneling as compared to that for positively-charged particles. Channeling of particles in either straight or bent crystals with polarized nuclei could be used for polarization and the analysis thereof of high-energy particles.

  5. Ultrafast optical spin echo for electron spins in semiconductors

    E-Print Network [OSTI]

    Susan M. Clark; Kai-Mei C. Fu; Qiang Zhang; Thaddeus D. Ladd; Colin Stanley; Yoshihisa Yamamoto

    2009-04-03T23:59:59.000Z

    Spin-based quantum computing and magnetic resonance techniques rely on the ability to measure the coherence time, T2, of a spin system. We report on the experimental implementation of all-optical spin echo to determine the T2 time of a semiconductor electron-spin system. We use three ultrafast optical pulses to rotate spins an arbitrary angle and measure an echo signal as the time between pulses is lengthened. Unlike previous spin-echo techniques using microwaves, ultrafast optical pulses allow clean T2 measurements of systems with dephasing times T2* fast in comparison to the timescale for microwave control. This demonstration provides a step toward ultrafast optical dynamic decoupling of spin-based qubits.

  6. Elastic and inelastic X-ray scattering studies of the low dimensional spin-1/2 quantum magnet TiOCl

    E-Print Network [OSTI]

    Abel, Eric T

    2007-01-01T23:59:59.000Z

    The ground state for a one dimensional spin 1/2 Heisenberg chain coupled to phonons is a dimerized singlet state known as a "spin-Peierls" state. Currently, the spin-Peierls state is realized in only a handful of known ...

  7. V O L U M E 59, NU M B E R 1 P H Y S I C A L R E V I E W L E T T E R S Observation of Spin Diffusion in Zero-Field Magnetic Resonance

    E-Print Network [OSTI]

    Suter, Dieter

    zero-field magnetic resonance, namely the potential for structure determination in solids without for a time ft, after which one component is converted back into population by a second pulse. The remainin gcoherence s decay over a time of the order of the spin-spin relaxation time Tz. During the mixing time rm

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

    SciTech Connect (OSTI)

    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

    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.

  9. Role of spin mixing conductance in spin pumping: Enhancement of spin pumping efficiency in Ta/Cu/Py structures

    SciTech Connect (OSTI)

    Deorani, Praveen; Yang, Hyunsoo, E-mail: eleyang@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore (Singapore)] [Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore (Singapore)

    2013-12-02T23:59:59.000Z

    From spin pumping measurements in Ta/Py devices for different thicknesses of Ta, we determine the spin Hall angle to be 0.021–0.033 and spin diffusion length to be 8?nm in Ta. We have also studied the effect of changing the properties of non-magnet/ferromagnet interface by adding a Cu interlayer. The experimental results show that the effective spin mixing conductance increases in the presence of Cu interlayer for Ta/Cu/Py devices whereas it decreases in Pt/Cu/Py devices. Our findings allow the tunability of the spin pumping efficiency by adding a thin interlayer at the non-magnet/ferromagnet interface.

  10. Spin Transport in Semiconductor heterostructures

    SciTech Connect (OSTI)

    Domnita Catalina Marinescu

    2011-02-22T23:59:59.000Z

    The focus of the research performed under this grant has been the investigation of spin transport in magnetic semiconductor heterostructures. The interest in these systems is motivated both by their intriguing physical properties, as the physical embodiment of a spin-polarized Fermi liquid, as well as by their potential applications as spintronics devices. In our work we have analyzed several different problems that affect the spin dynamics in single and bi-layer spin-polarized two-dimensional (2D) systems. The topics of interests ranged from the fundamental aspects of the electron-electron interactions, to collective spin and charge density excitations and spin transport in the presence of the spin-orbit coupling. The common denominator of these subjects is the impact at the macroscopic scale of the spin-dependent electron-electron interaction, which plays a much more subtle role than in unpolarized electron systems. Our calculations of several measurable parameters, such as the excitation frequencies of magneto-plasma modes, the spin mass, and the spin transresistivity, propose realistic theoretical estimates of the opposite-spin many-body effects, in particular opposite-spin correlations, that can be directly connected with experimental measurements.

  11. Quantum superintegrable system for arbitrary spin

    E-Print Network [OSTI]

    G. Pronko

    2007-09-20T23:59:59.000Z

    In [1] was considered the superintegrable system which describes the magnetic dipole with spin 1/2 (neutron) in the field of linear current. Here we present its generalization for any spin which preserves superintegrability. The dynamical symmetry stays the same as it is for spin 1/2.

  12. Magnetism in metal-organic capsules

    E-Print Network [OSTI]

    Atwood, Jerry L.

    2010-01-01T23:59:59.000Z

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

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

    SciTech Connect (OSTI)

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

    2013-06-01T23:59:59.000Z

    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.

  14. 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)

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

    2013-06-01T23:59:59.000Z

    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.

  15. 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)

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

    2013-06-01T23:59:59.000Z

    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 tomore »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.« less

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

    SciTech Connect (OSTI)

    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

    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.

  17. Nuclear spin circular dichroism

    SciTech Connect (OSTI)

    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

    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.

  18. Spinning superconducting electrovacuum soliton

    E-Print Network [OSTI]

    Irina Dymnikova

    2006-07-24T23:59:59.000Z

    In nonlinear electrodynamics coupled to general relativity and satisfying the weak energy condition, a spherically symmetric electrically charged electrovacuum soliton has obligatory de Sitter center in which the electric field vanishes while the energy density of electromagnetic vacuum achieves its maximal value. De Sitter vacuum supplies a particle with the finite positive electromagnetic mass related to breaking of space-time symmetry from the de Sitter group in the origin. By the G\\"urses-G\\"ursey algorithm based on the Newman-Trautman technique it is transformed into a spinning electrovacuum soliton asymptotically Kerr-Newman for a distant observer. De Sitter center becomes de Sitter equatorial disk which has both perfect conductor and ideal diamagnetic properties. The interior de Sitter vacuum disk displays superconducting behavior within a single spinning soliton. This behavior found for an arbitrary nonlinear lagrangian ${\\cal L}(F)$, is generic for the class of regular spinning electrovacuum solutions describing both black holes and particle-like structures.

  19. 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

  20. Electrical spin injection using GaCrN in a GaN based spin light emitting diode

    SciTech Connect (OSTI)

    Banerjee, D.; Ganguly, S.; Saha, D., E-mail: dipankarsaha@iitb.ac.in [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India); IITB-Monash Research Academy, Indian Institute of Technology Bombay, Mumbai 400076 (India); Adari, R.; Sankaranarayan, S.; Kumar, A. [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India)] [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India); Aldhaheri, R. W.; Hussain, M. A.; Balamesh, A. S. [Department of Electrical and Computer Engineering, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)] [Department of Electrical and Computer Engineering, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

    2013-12-09T23:59:59.000Z

    We have demonstrated electrical spin-injection from GaCrN dilute magnetic semiconductor (DMS) in a GaN-based spin light emitting diode (spin-LED). The remanent in-plane magnetization of the thin-film semiconducting ferromagnet has been used for introducing the spin polarized electrons into the non-magnetic InGaN quantum well. The output circular polarization obtained from the spin-LED closely follows the normalized in-plane magnetization curve of the DMS. A saturation circular polarization of ?2.5% is obtained at 200?K.

  1. Germanium Nanowire Spin-Valve Device (DMR-0819860)

    E-Print Network [OSTI]

    Petta, Jason

    Germanium Nanowire Spin-Valve Device (DMR-0819860) E-S Liu, J. Nah, K.Varahramyan, and E. Tutuc (Univ. of Texas at Austin) Figure 1 The spin-valve device comprised of a Ge nanowire bracketed by two in direction, the spin current is suppressed (spin-valve action). An applied magnetic field By is used

  2. acoustic electron spin resonance: Topics by E-print Network

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

    of electrons with spin-up and electrons with spin-down. In terms of new model we consider propagation of waves in magnetized plasmas of degenerate electrons and motionless ions. We...

  3. Spin Polarized Conductance in Hybrid Graphene Nanoribbons Using 5-7 Defects

    SciTech Connect (OSTI)

    Sumpter, Bobby G [ORNL; Meunier, Vincent [ORNL; Cruz Silva, Eduardo [ORNL; Terrones Maldonado, Humberto [ORNL; Terrones Maldonado, Mauricio [ORNL; Lopez, Florentino [IPICyT; Botello Mendez, Andres R [ORNL

    2009-01-01T23:59:59.000Z

    We present a class of intramolecular graphene heterojunctions and use first-principles density functional calculations to describe their electronic, magnetic, and transport properties. The hybrid graphene and hybrid graphene nanoribbons have both armchair and zigzag features that are separated by an interface made up of pentagonal and heptagonal carbon rings. Contrary to conventional graphene sheets, the computed electronic density of states indicates that all hybrid graphene and nanoribbon systems are metallic. Hybrid nanoribbons are found to exhibit a remarkable width-dependent magnetic behavior and behave as spin polarized conductors.

  4. Spinning angle optical calibration apparatus

    DOE Patents [OSTI]

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

    1991-01-01T23:59:59.000Z

    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.

  5. Spin waves in the (

    SciTech Connect (OSTI)

    Lipscombe, O. J. [University of Tennessee, Knoxville (UTK); Chen, G. F. [The Institute of Physics, Chinese Academy of Sciences; Fang, Chen [Purdue University; Perring, T. G. [ISIS Facility, Rutherford Appleton Laboratory; Abernathy, Douglas L [ORNL; Christianson, Andrew D [ORNL; Egami, Takeshi [ORNL; Wang, Nanlin [The Institute of Physics, Chinese Academy of Sciences; Hu, Jiangping [Purdue University and Chinese Academy of Sciences; Dai, Pengcheng [University of Tennessee, Knoxville (UTK)

    2011-01-01T23:59:59.000Z

    We use neutron scattering to show that spin waves in the iron chalcogenide Fe{sub 1.05}Te display novel dispersion clearly different from both the first principles density functional calculations and recent observations in the related iron pnictide CaFe{sub 2}As{sub 2}. By fitting to a Heisenberg Hamiltonian, we find that although the nearest-neighbor exchange couplings in the two systems are quite different, their next-nearest-neighbor (NNN) couplings are similar. This suggests that superconductivity in the pnictides and chalcogenides share a common magnetic origin that is intimately associated with the NNN magnetic coupling between the irons.

  6. Discussion on spin-flip synchrotron radiation

    E-Print Network [OSTI]

    V. A. Bordovitsyn; V. S. Gushchina; A. N. Myagkii

    2001-02-12T23:59:59.000Z

    Quantum spin-flip transitions are of great importance in the synchrotron radiation theory. For better understanding of the nature of this phenomenon, it is necessary to except the effects connected with the electric charge radiation from observation. This fact explains the suggested choice of the spin-flip radiation model in the form of radiation of the electric neutral Dirac-Pauli particle moving in the homogeneous magnetic field. It is known that in this case, the total radiation in the quantum theory is conditioned by spin-flip transitions. The idea is that spin-flip radiation is represented as a nonstationary process connected with spin precession. We shall shown how to construct a solution of the classical equation of the spin precession in the BMT theory having the exact solution of the Dirac-Pauli equation.Thus, one will find the connection of the quantum spin-flip transitions with classical spin precession.

  7. Novel bias-field-free spin transfer oscillator

    SciTech Connect (OSTI)

    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

    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.

  8. Spin injection and transport in semiconductor and metal nanostructures

    E-Print Network [OSTI]

    Zhu, Lei

    2009-01-01T23:59:59.000Z

    spin-momentum-transfer effect (SMT), which was theoreticallyaccess memory (DRAM). SMT utilizes the momentum transferto magnetize a unit cell. This SMT effect becomes prominent

  9. Noble gas magnetic resonator

    DOE Patents [OSTI]

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

    2014-04-15T23:59:59.000Z

    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.

  10. Alternating magnetic anisotropy of Li 2 ( Li 1 - x T x ) N ( T = Mn , Fe , Co , and Ni )

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

    Jesche, A.; Ke, L.; Jacobs, J. L.; Harmon, B.; Houk, R. S.; Canfield, P. C.

    2015-05-01T23:59:59.000Z

    Substantial amounts of the transition metals Mn, Fe, Co, and Ni can be substituted for Li in single crystalline Li?(Li1-xTx)N. Isothermal and temperature-dependent magnetization measurements reveal local magnetic moments with magnitudes significantly exceeding the spin-only value. The additional contributions stem from unquenched orbital moments that lead to rare-earth-like behavior of the magnetic properties. Accordingly, extremely large magnetic anisotropies have been found. Most notably, the magnetic anisotropy alternates as easy plane?easy axis?easy plane?easy axis when progressing from T = Mn ? Fe ? Co ? Ni. This behavior can be understood based on a perturbation approach in an analytical, single-ion model. The calculated magnetic anisotropies show surprisingly good agreement with the experiment and capture the basic features observed for the different transition metals.

  11. Alternating magnetic anisotropy of Li 2 ( Li 1 - x T x ) N ( T = Mn , Fe , Co , and Ni )

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

    Jesche, A.; Ke, L.; Jacobs, J. L.; Harmon, B.; Houk, R. S.; Canfield, P. C.

    2015-05-01T23:59:59.000Z

    Substantial amounts of the transition metals Mn, Fe, Co, and Ni can be substituted for Li in single crystalline Li?(Li1-xTx)N. Isothermal and temperature-dependent magnetization measurements reveal local magnetic moments with magnitudes significantly exceeding the spin-only value. The additional contributions stem from unquenched orbital moments that lead to rare-earth-like behavior of the magnetic properties. Accordingly, extremely large magnetic anisotropies have been found. Most notably, the magnetic anisotropy alternates as easy plane?easy axis?easy plane?easy axis when progressing from T = Mn ? Fe ? Co ? Ni. This behavior can be understood based on a perturbation approach in an analytical, single-ion model.more »The calculated magnetic anisotropies show surprisingly good agreement with the experiment and capture the basic features observed for the different transition metals.« less

  12. In-field {sup 57}Fe Mössbauer spectroscopy below spin-flop transition in powdered troilite (FeS) mineral

    SciTech Connect (OSTI)

    Cuda, Jan, E-mail: jan.cuda@upol.cz; Tucek, Jiri; Filip, Jan; Malina, Ondrej; Krizek, Michal; Zboril, Radek [Regional Centre of Advanced Technologies and Materials, Departments of Experimental Physics and Physical Chemistry, Faculty of Science, Palacký University in Olomouc, 17. listopadu 1192/12, 771 46 Olomouc (Czech Republic); Kohout, Tomas [Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki University, Finland and Institute of Geology, Academy of Sciences of the Czech Republic v.v.i., Rozvojová 269, 165 00 Prague (Czech Republic)

    2014-10-27T23:59:59.000Z

    Powdered troilite (FeS), extracted from the Cape York IIIA octahedrite meteorite, was investigated employing in-field {sup 57}Fe Mössbauer spectroscopy. The study identified a typical behavior of polycrystalline antiferromagnetic material under external magnetic fields. The in-field evolution of the {sup 57}Fe Mössbauer spectra showed that the spin-flop transition in the FeS system occurs at a field higher than 5 T.

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

    SciTech Connect (OSTI)

    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

    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.

  14. Large amplitude spin torque vortex oscillations at zero external field using a perpendicular spin polarizer

    SciTech Connect (OSTI)

    Dussaux, A.; Rache Salles, B.; Jenkins, A. S.; Bortolotti, P.; Grollier, J.; Cros, V.; Fert, A. [Unité Mixte de Physique CNRS/Thales and Université Paris Sud 11, 1 Ave. A. Fresnel, 91767 Palaiseau (France); Grimaldi, E., E-mail: eva.grimaldi@thalesgroup.com [Unité Mixte de Physique CNRS/Thales and Université Paris Sud 11, 1 Ave. A. Fresnel, 91767 Palaiseau (France); CNES, 1 Avenue Edouard Belin, 31400 Toulouse (France); Khvalkovskiy, A. V. [Unité Mixte de Physique CNRS/Thales and Université Paris Sud 11, 1 Ave. A. Fresnel, 91767 Palaiseau (France); A.M. Prokhorov General Physics Institute of RAS, Vavilova Str. 38, 119991 Moscow (Russian Federation); Kubota, H.; Fukushima, A.; Yakushiji, K.; Yuasa, S. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan)

    2014-07-14T23:59:59.000Z

    We investigate the microwave response of a spin transfer vortex based oscillator in a magnetic tunnel junction with an in-plane reference layer combined with a spin valve with an out-of-plane magnetization spin polarizing layer. The main advantage of this perpendicular spin polarizer is to induce a large spin transfer force even at zero magnetic field, thus leading to a record emitted power (up to 0.6??W) associated to a very narrow spectral linewidth of a few hundreds of kHz. The characteristics of this hybrid vortex based spin transfer nano-oscillator obtained at zero field and room temperature are of great importance for applications based on rf spintronic devices as integrated and tunable microwave source and/or microwave detector.

  15. artificial molecular magnets: Topics by E-print Network

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

    2013-01-04 18 Magnetic anisotropy of elongated thin ferromagnetic nano-islands for artificial spin ice arrays Physics Websites Summary: Magnetic anisotropy of elongated thin...

  16. artificial magnetic fields: Topics by E-print Network

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

    Galea 2003-02-10 74 Magnetic anisotropy of elongated thin ferromagnetic nano-islands for artificial spin ice arrays Physics Websites Summary: Magnetic anisotropy of elongated thin...

  17. artificial magnetic response: Topics by E-print Network

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

    2013-01-04 13 Magnetic anisotropy of elongated thin ferromagnetic nano-islands for artificial spin ice arrays Physics Websites Summary: Magnetic anisotropy of elongated thin...

  18. Characteristics of Graphitic Films for Carbon Based Magnetism and Electronics

    E-Print Network [OSTI]

    Hong, Jeongmin

    2009-01-01T23:59:59.000Z

    Spintronics: a spin-based electronics vision for theBased Magnetism and Electronics A Dissertation submitted inBased Magnetism and Electronics by Jeongmin Hong Doctor of

  19. Cavity cooling of an ensemble spin system

    E-Print Network [OSTI]

    Christopher J. Wood; Troy W. Borneman; David G. Cory

    2014-02-24T23:59:59.000Z

    We describe how sideband cooling techniques may be applied to large spin ensembles in magnetic resonance. Using the Tavis-Cummings model in the presence of a Rabi drive, we solve a Markovian master equation describing the joint spin-cavity dynamics to derive cooling rates as a function of ensemble size. Our calculations indicate that the coupled angular momentum subspaces of a spin ensemble containing roughly $10^{11}$ electron spins may be polarized in a time many orders of magnitude shorter than the typical thermal relaxation time. The described techniques should permit efficient removal of entropy for spin-based quantum information processors and fast polarization of spin samples. The proposed application of a standard technique in quantum optics to magnetic resonance also serves to reinforce the connection between the two fields, which has recently begun to be explored in further detail due to the development of hybrid designs for manufacturing noise-resilient quantum devices.

  20. LaSrVO4: a candidate for the spin-orbital liquid state

    SciTech Connect (OSTI)

    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

    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.

  1. INTERPRETING ERUPTIVE BEHAVIOR IN NOAA AR 11158 VIA THE REGION'S MAGNETIC ENERGY AND RELATIVE-HELICITY BUDGETS

    SciTech Connect (OSTI)

    Tziotziou, Kostas; Georgoulis, Manolis K. [Research Center for Astronomy and Applied Mathematics (RCAAM) Academy of Athens, 4 Soranou Efesiou Street, Athens, GR-11527 (Greece); Liu Yang [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305-4085 (United States)

    2013-08-01T23:59:59.000Z

    In previous works, we introduced a nonlinear force-free method that self-consistently calculates the instantaneous budgets of free magnetic energy and relative magnetic helicity in solar active regions (ARs). Calculation is expedient and practical, using only a single vector magnetogram per computation. We apply this method to a time series of 600 high-cadence vector magnetograms of the eruptive NOAA AR 11158 acquired by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory over a five-day observing interval. Besides testing our method extensively, we use it to interpret the dynamical evolution in the AR, including eruptions. We find that the AR builds large budgets of both free magnetic energy and relative magnetic helicity, sufficient to power many more eruptions than the ones it gave within the interval of interest. For each of these major eruptions, we find eruption-related decreases and subsequent free-energy and helicity budgets that are consistent with the observed eruption (flare and coronal mass ejection (CME)) sizes. In addition, we find that (1) evolution in the AR is consistent with the recently proposed (free) energy-(relative) helicity diagram of solar ARs, (2) eruption-related decreases occur before the flare and the projected CME-launch times, suggesting that CME progenitors precede flares, and (3) self terms of free energy and relative helicity most likely originate from respective mutual terms, following a progressive mutual-to-self conversion pattern that most likely stems from magnetic reconnection. This results in the non-ideal formation of increasingly helical pre-eruption structures and instigates further research on the triggering of solar eruptions with magnetic helicity firmly placed in the eruption cadre.

  2. The spin Hall angle and spin diffusion length of Pd measured by spin pumping and microwave photoresistance

    SciTech Connect (OSTI)

    Tao, X. D.; Feng, Z.; Miao, B. F.; Sun, L.; You, B.; Wu, D.; Du, J.; Zhang, W.; Ding, H. F., E-mail: hfding@nju.edu.cn [Department of Physics, National Laboratory of Solid State Microstructures, Nanjing University, 22 Hankou Road, Nanjing 210093 (China)

    2014-05-07T23:59:59.000Z

    We present the experimental study of the spin Hall angle (SHA) and spin diffusion length of Pd with the spin pumping and microwave photoresistance effects. The Py/Pd bilayer stripes are excited with an out-of-plane microwave magnetic field. The pure spin current is thus pumped and transforms into charge current via the inverse spin Hall effect (ISHE) in Pd layer, yielding an ISHE voltage. The ISHE voltage can be distinguished from the unwanted signal caused by the anisotropic magnetoresistance according to their different symmetries. Together with Pd thickness dependent measurements of in and out-of-plane precessing angles and effective spin mixing conductance, the SHA and spin-diffusion length of Pd are quantified as 0.0056?±?0.0007 and 7.3?±?0.7?nm, respectively.

  3. RHIC spin flipper AC dipole controller

    SciTech Connect (OSTI)

    Oddo, P.; Bai, M.; Dawson, C.; Gassner, D.; Harvey, M.; Hayes, T.; Mernick, K.; Minty, M.; Roser, T.; Severino, F.; Smith, K.

    2011-03-28T23:59:59.000Z

    The RHIC Spin Flipper's five high-Q AC dipoles which are driven by a swept frequency waveform require precise control of phase and amplitude during the sweep. This control is achieved using FPGA based feedback controllers. Multiple feedback loops are used to and dynamically tune the magnets. The current implementation and results will be presented. Work on a new spin flipper for RHIC (Relativistic Heavy Ion Collider) incorporating multiple dynamically tuned high-Q AC-dipoles has been developed for RHIC spin-physics experiments. A spin flipper is needed to cancel systematic errors by reversing the spin direction of the two colliding beams multiple times during a store. The spin flipper system consists of four DC-dipole magnets (spin rotators) and five AC-dipole magnets. Multiple AC-dipoles are needed to localize the driven coherent betatron oscillation inside the spin flipper. Operationally the AC-dipoles form two swept frequency bumps that minimize the effect of the AC-dipole dipoles outside of the spin flipper. Both AC bumps operate at the same frequency, but are phase shifted from each other. The AC-dipoles therefore require precise control over amplitude and phase making the implementation of the AC-dipole controller the central challenge.

  4. Journal of Superconductivity: Incorporating Novel Magnetism, Vol. 16, No. 2, April 2003 ( C 2003) Spin-Photocurrent in p-SiGe Quantum Wells

    E-Print Network [OSTI]

    Ganichev, Sergey

    ) Spin-Photocurrent in p-SiGe Quantum Wells under Terahertz Laser Irradiation V. V. Bel'kov,1,2 S. D effect (CPGE) in SiGe structures is presented. It is shown that the CPGE becomes possible because. KEY WORDS: SiGe-QWs; photogalvanic effect; Rashba term. 1. INTRODUCTION Recently it has been

  5. Optically Enhanced Magnetic Resonance

    E-Print Network [OSTI]

    Suter, Dieter

    , like spatial structures or molecular dynamics. While the direct excitation of nuclear spin transitions.1 Motivation The physical mechanism of nuclear magnetic resonance spectroscopy, the excitation of transitions light for polarizing the spin system or for observing its dynamics. This possibility arises from

  6. Magnetic behavior in Cr{sub 2}@Ge{sub n} (1?n?12) clusters: A density functional investigation

    SciTech Connect (OSTI)

    Dhaka, Kapil, E-mail: kapil.dhaka@pilani.bits-pilani.ac.in; Trivedi, Ravi, E-mail: kapil.dhaka@pilani.bits-pilani.ac.in; Bandyopadhyay, Debashis, E-mail: kapil.dhaka@pilani.bits-pilani.ac.in [Physics Department, Birla Institute of Technology and Science, Pilani-333031, Rajasthan (India)

    2014-04-24T23:59:59.000Z

    With a goal to produce magnetic moment in Cr{sub 2} Doped Ge{sub n} clusters which will be useful for practical applications, we have considered the structure and magnetic properties of Pure Germanium clusters and substitutionally doped it with Cr dimer to produce Cr{sub 2}@Ge{sub n} clusters. As the first step of calculation, geometrical optimizations of the nanoclusters have been done. These optimized geometries have been used in calculate the average binding energy per atom (BE), HOMO-LUMO gap and hence the relative stability of the clusters. These parameters have been demonstrated as structural and electronic properties of the clusters. Gap between highest occupied molecular orbital and lowest unoccupied molecular orbital indicate cluster to be a potential motif for generating magnetic cluster assembled materials. Based on these values a comparative study on different sized clusters has been done in order to understand the origin of structures, electronic and magnetic properties of Cr{sub 2}@Ge{sub n} nanoclusters.

  7. 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]

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

    2014-05-23T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  9. Temperature dependent spin transport properties of platinum inferred from spin Hall magnetoresistance measurements

    SciTech Connect (OSTI)

    Meyer, Sibylle, E-mail: sibylle.meyer@wmi.badw-muenchen.de; Althammer, Matthias; Geprägs, Stephan; Opel, Matthias; Goennenwein, Sebastian T. B. [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Gross, Rudolf [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Physik-Department, Technische Universität München, 85748 Garching (Germany)

    2014-06-16T23:59:59.000Z

    We study the temperature dependence of the spin Hall magnetoresistance (SMR) in yttrium iron garnet/platinum hybrid structures via magnetization orientation dependent magnetoresistance measurements. Our experiments show a decrease of the SMR magnitude with decreasing temperature. Using the sensitivity of the SMR to the spin transport properties of the normal metal, we interpret our data in terms of a decrease of the spin Hall angle in platinum from 0.11 at room temperature to 0.075 at 10?K, while the spin diffusion length and the spin mixing conductance of the ferrimagnetic insulator/normal metal interface remain almost constant.

  10. Optically Detected Magnetic Resonance Studies on ?-conjugated semiconductor systems

    SciTech Connect (OSTI)

    Chen, Ying

    2011-12-06T23:59:59.000Z

    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.

  11. Spin-valve photodiode Ian Appelbaum,a)

    E-Print Network [OSTI]

    Russell, Kasey

    Spin-valve photodiode Ian Appelbaum,a) D. J. Monsma, K. J. Russell, V. Narayanamurti, and C. M; accepted 28 August 2003 An optical spin-valve effect is observed using sub-bandgap internal photoemission the ``spin-valve'' effect SVE , because the relative magnetizations of these layers, and thus the flow

  12. Emergent spin

    SciTech Connect (OSTI)

    Creutz, Michael, E-mail: creutz@bnl.gov

    2014-03-15T23:59:59.000Z

    Quantum mechanics and relativity in the continuum imply the well known spin–statistics connection. However for particles hopping on a lattice, there is no such constraint. If a lattice model yields a relativistic field theory in a continuum limit, this constraint must “emerge” for physical excitations. We discuss a few models where a spin-less fermion hopping on a lattice gives excitations which satisfy the continuum Dirac equation. This includes such well known systems such as graphene and staggered fermions. -- Highlights: •The spin–statistics theorem is not required for particles on a lattice. •Spin emerges dynamically when spinless fermions have a relativistic continuum limit. •Graphene and staggered fermions are examples of this phenomenon. •The phenomenon is intimately tied to chiral symmetry and fermion doubling. •Anomaly cancellation is a crucial feature of any valid lattice fermion action.

  13. $?^{-}$, $?^{* -}$, $?^{* -}$ and $?^{-}$ decuplet baryon magnetic moments

    E-Print Network [OSTI]

    Milton Dean Slaughter

    2011-04-04T23:59:59.000Z

    The properties of the ground state $U$-Spin $={3/2}$ baryon decuplet magnetic moments $\\Delta^{-}$, $\\Xi^{* -}$, $\\Sigma^{* -}$ and $\\Omega^{-}$ and their ground state spin 1/2 cousins $p$, $n$, $\\Lambda$, $\\Sigma^{+}$, $\\Sigma^{0}$, $\\Sigma^{-}$, $\\Xi^{+}$, and $\\Xi^{-}$ have been studied for many years with a modicum of success. The magnetic moments of many are yet to be determined. Of the decuplet baryons, only the magnetic moment of the $\\Omega^{-}$ has been accurately determined. We calculate the magnetic moments of the \\emph{physical} decuplet $U$-Spin $={3/2}$ quartet members without ascribing any specific form to their quark structure or intra-quark interactions.

  14. Quantum correlations in spin models

    SciTech Connect (OSTI)

    Zhang Guofeng, E-mail: gf1978zhang@buaa.edu.cn [Department of Physics, School of Physics and Nuclear Energy Engineering, Beihang University, Xueyuan Road No. 37, Beijing 100191 (China); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Fan Heng; Ji Ailing [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Jiang Zhaotan [Department of Physics, Beijing Institute of Technology, Beijing 100081 (China); Abliz, Ahmad [School of Mathematics, Physics and Informatics, Xinjiang Normal University, Urumchi 830054 (China); Liu Wuming [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2011-10-15T23:59:59.000Z

    Bell nonlocality, entanglement and nonclassical correlations are different aspects of quantum correlations for a given state. There are many methods to measure nonclassical correlations. In this paper, nonclassical correlations in two-qubit spin models are measured by the use of measurement-induced disturbance (MID) [S. Luo, Phys. Rev. A 77 (2008) 022301] and geometric measure of quantum discord (GQD) [B. Dakic, V. Vedral, C. Brukner, Phys. Rev. Lett. 105 (2010) 190502]. Their dependences on external magnetic field, spin-spin coupling, and the Dzyaloshinskii-Moriya (DM) interaction are presented in detail. We also compare Bell nonlocality, entanglement measured by concurrence, MID and GQD and illustrate their different characteristics. - Highlights: > Various quantum correlations in spin models are investigated. > Nonclassical correlations are measured by measurement-induced disturbance and Geometric measure of quantum discord. > Also, we investigate Bell nonlocality and concurrence. > We compare these quantum quantities and illustrate their different characteristics.

  15. Distinguishing spin pumping from spin rectification in a Pt/Py bilayer through angle dependent line shape analysis

    SciTech Connect (OSTI)

    Bai, Lihui; Hyde, P.; Hu, C.-M. [Department of Physics and Astronomy, University of Manitoba, Winnipeg R3T 2N2 (Canada)] [Department of Physics and Astronomy, University of Manitoba, Winnipeg R3T 2N2 (Canada); Feng, Z.; Ding, H. F. [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, 22 Hankou Road, Nanjing 210093 (China)] [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, 22 Hankou Road, Nanjing 210093 (China)

    2013-06-17T23:59:59.000Z

    A pure spin current driven by spin pumping is converted to a DC voltage and detected electrically in a Py/Pt bilayer sample. This DC voltage mixes with a DC voltage produced through spin rectification. The ferromagnetic resonance line shape strongly depends on the microwave magnetic h field distribution. We have systematically studied the line shapes by changing the external magnetic field orientation in plane of a Pt/Py bilayer. A method is demonstrated which allows us to calculate the microwave h field vector distribution, and distinguish spin pumping from spin rectification.

  16. Dynamic control of spin wave spectra using spin-polarized currents

    SciTech Connect (OSTI)

    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

    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.

  17. Classical gravitational spin-spin interaction

    E-Print Network [OSTI]

    W. B. Bonnor

    2002-01-30T23:59:59.000Z

    I obtain an exact, axially symmetric, stationary solution of Einstein's equations for two massless spinning particles. The term representing the spin-spin interaction agrees with recently published approximate work. The spin-spin force appears to be proportional to the inverse fourth power of the coordinate distance between the particles.

  18. One dimensional electron spin imaging for single spin detection and manipulation using a gradient field 

    E-Print Network [OSTI]

    Shin, Chang-Seok

    2009-05-15T23:59:59.000Z

    magnetic field gradients. These fabricated devices are used to demonstrate this subwavelength imaging technique by imaging single electron spins of the nitrogen-vacancy (NV) defect in diamond. In this demonstration, multiple NV defects, unresolved in a...

  19. One dimensional electron spin imaging for single spin detection and manipulation using a gradient field

    E-Print Network [OSTI]

    Shin, Chang-Seok

    2009-05-15T23:59:59.000Z

    magnetic field gradients. These fabricated devices are used to demonstrate this subwavelength imaging technique by imaging single electron spins of the nitrogen-vacancy (NV) defect in diamond. In this demonstration, multiple NV defects, unresolved in a...

  20. High-spin nuclear spectroscopy

    SciTech Connect (OSTI)

    Diamond, R.M.

    1986-07-01T23:59:59.000Z

    High-spin spectroscopy is the study of the changes in nuclear structure, properties, and behavior with increasing angular momentum. It involves the complex interplay between collective and single-particle motion, between shape and deformation changes, particle alignments, and changes in the pairing correlations. A review of progress in theory, experimentation, and instrumentation in this field is given. (DWL)

  1. Giant enhancement of spin pumping in the out-of-phase precession mode

    SciTech Connect (OSTI)

    Takahashi, S. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2014-02-03T23:59:59.000Z

    We theoretically study the spin pumping from the two ferromagnetic layers embedded in a normal metal and investigate the spin current and spin accumulation generated by the precessing magnetizations, focusing on their dependence on the relative precessional motion and the layer separation. We demonstrate a giant enhancement of spin pumping induced in the out-of-phase precession mode of the magnetizations in which the pumped spin current and spin accumulation are greatly enhanced compared to those in the in-phase precession mode. The giant enhancement of spin pumping is discussed in relation to an enhanced Gilbert damping.

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

    SciTech Connect (OSTI)

    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

    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.

  3. Chimera order in spin systems

    E-Print Network [OSTI]

    Rajeev Singh; Subinay Dasgupta; Sitabhra Sinha

    2010-11-23T23:59:59.000Z

    Homogeneous populations of oscillators have recently been shown to exhibit stable coexistence of coherent and incoherent regions. Generalizing the concept of chimera states to the context of order-disorder transition in systems at thermal equilibrium, we show analytically that such complex ordering can appear in a system of Ising spins, possibly the simplest physical system exhibiting this phenomenon. We also show numerically the existence of chimera ordering in 3-dimensional spin systems that model layered magnetic materials, suggesting possible means of experimentally observing such states.

  4. Exotic quantum magnetism and superfluidity in optical lattices

    E-Print Network [OSTI]

    Hung, Hsiang-Hsuan

    2011-01-01T23:59:59.000Z

    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

  5. Long-Time Relaxation on Spin Lattice as Manifestation of Chaotic Dynamics

    E-Print Network [OSTI]

    Boris V. Fine

    2004-08-10T23:59:59.000Z

    The long-time behavior of the infinite temperature spin correlation functions describing the free induction decay in nuclear magnetic resonance and intermediate structure factors in inelastic neutron scattering is considered. These correlation functions are defined for one-, two- and three-dimensional infinite lattices of interacting spins both classical and quantum. It is shown that, even though the characteristic timescale of the long-time decay of the correlation functions considered is non-Markovian, the generic functional form of this decay is either simple exponential or exponential multiplied by cosine. This work contains (i) summary of the existing experimental and numerical evidence of the above asymptotic behavior; (ii) theoretical explanation of this behavior; and (iii) semi-empirical analysis of various factors discriminating between the monotonic and the oscillatory long-time decays. The theory is based on a fairly strong conjecture that, as a result of chaos generated by the spin dynamics, a Brownian-like Markovian description can be applied to the long-time properties of ensemble average quantities on a non-Markovian timescale. The formalism resulting from that conjecture can be described as ``correlated diffusion in finite volumes.''

  6. Two Wien Filter Spin Flipper

    SciTech Connect (OSTI)

    Grames, J M; Benesch, J F; Clark, J; Hansknecht, J; Kazimi, R; Machie, D; Poelker, M; Stutzman, M L; Suleiman, R

    2011-03-01T23:59:59.000Z

    A new 4pi spin manipulator composed of two Wien filters oriented orthogonally and separated by two solenoids has been installed at the CEBAF/Jefferson Lab photoinjector. The new spin manipulator is used to precisely set the electron spin direction at an experiment in any direction (in or out of plane of the accelerator) and provides the means to reverse, or flip, the helicity of the electron beam on a daily basis. This reversal is being employed to suppress systematic false asymmetries that can jeopardize challenging parity violation experiments that strive to measure increasingly small physics asymmetries [*,**,***]. The spin manipulator is part of the ultra-high vacuum polarized electron source beam line and has been successfully operated with 100keV and 130keV electron beam at high current (>100 microAmps). A unique feature of the device is that spin-flipping requires only the polarity of one solenoid magnet be changed. Performance characteristics of the Two Wien Filter Spin Flipper will be summarized.

  7. Motional Spin Relaxation in Large Electric Fields

    E-Print Network [OSTI]

    Schmid, Riccardo; Filippone, B W

    2008-01-01T23:59:59.000Z

    We discuss the precession of spin-polarized Ultra Cold Neutrons (UCN) and $^{3}\\mathrm{He}$ atoms in uniform and static magnetic and electric fields and calculate the spin relaxation effects from motional $v\\times E$ magnetic fields. Particle motion in an electric field creates a motional $v\\times E$ magnetic field, which when combined with collisions, produces variations of the total magnetic field and results in spin relaxation of neutron and $^{3}\\mathrm{He}$ samples. The spin relaxation times $T_{1}$ (longitudinal) and $T_{2}$ (transverse) of spin-polarized UCN and $^{3}\\mathrm{He}$ atoms are important considerations in a new search for the neutron Electric Dipole Moment at the SNS \\emph{nEDM} experiment. We use a Monte Carlo approach to simulate the relaxation of spins due to the motional $v\\times E$ field for UCN and for $^{3}\\mathrm{He}$ atoms at temperatures below $600 \\mathrm{mK}$. We find the relaxation times for the neutron due to the $v\\times E$ effect to be long compared to the neutron lifetime, ...

  8. Motional Spin Relaxation in Large Electric Fields

    E-Print Network [OSTI]

    Riccardo Schmid; B. Plaster; B. W. Filippone

    2008-07-02T23:59:59.000Z

    We discuss the precession of spin-polarized Ultra Cold Neutrons (UCN) and $^{3}$He atoms in uniform and static magnetic and electric fields and calculate the spin relaxation effects from motional $v\\times E$ magnetic fields. Particle motion in an electric field creates a motional $v\\times E$ magnetic field, which when combined with collisions, produces variations of the total magnetic field and results in spin relaxation of neutron and $^{3}$He samples. The spin relaxation times $T_{1}$ (longitudinal) and $T_{2}$ (transverse) of spin-polarized UCN and $^{3}$He atoms are important considerations in a new search for the neutron Electric Dipole Moment at the SNS \\emph{nEDM} experiment. We use a Monte Carlo approach to simulate the relaxation of spins due to the motional $v\\times E$ field for UCN and for $^{3}$He atoms at temperatures below $600,\\mathrm{mK}$. We find the relaxation times for the neutron due to the $v\\times E$ effect to be long compared to the neutron lifetime, while the $^{3}$He relaxation times may be important for the \\emph{nEDM} experiment.

  9. Kinetic control of structural and magnetic states in LuBaCo4O7.

    SciTech Connect (OSTI)

    Avci, S.; Chmaissem, O.; Zheng, H.; Huq, A.; Khalyavin, D.; Stephens, P.; Suchomel, M.; Manuel, P.; Mitchell, J. (X-Ray Science Division); (Northern Illinois University); (Oak Ridge National Laboratory); (ISIS, Rutherford Appleton Laboratory); (Stony Brook University)

    2012-01-01T23:59:59.000Z

    The RBaCo{sub 4}O{sub 7} (R = Ca, Y, Tb, Ho, Tm, Yb, Lu) compounds provide a novel topology for studying the competition between triangular geometry and magnetic order. Here, we report the structural and magnetic behavior of the Lu member of this series via neutron and synchrotron x-ray diffraction, magnetization, and resistivity measurements. We determined sequential phase transitions and a strong competition between a stable and a metastable low-temperature state that critically depends on controlled cooling rates and the associated heat removal kinetics. No evidence for long-range ordered magnetism was detected by neutron diffraction at any temperature. However, very slow spin dynamics are evidenced by time-dependent neutron diffraction measurements and can be explained by several competing magnetic phases with incommensurate short-range correlations coexisting in this material.

  10. Low field magnetic resonance imaging

    DOE Patents [OSTI]

    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

    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.

  11. Localization of disordered bosons and magnets in random fields

    SciTech Connect (OSTI)

    Yu, Xiaoquan, E-mail: yuxq2008@gmail.com [International School for Advanced Studies (SISSA), via Bonomea 265, 34136 Trieste (Italy) [International School for Advanced Studies (SISSA), via Bonomea 265, 34136 Trieste (Italy); New Zealand Institute for Advanced Study, Centre for Theoretical Chemistry and Physics, Massey University, Auckland 0745 (New Zealand); Müller, Markus, E-mail: markusm@ictp.it [The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151 Trieste (Italy)] [The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151 Trieste (Italy)

    2013-10-15T23:59:59.000Z

    We study localization properties of disordered bosons and spins in random fields at zero temperature. We focus on two representatives of different symmetry classes, hard-core bosons (XY magnets) and Ising magnets in random transverse fields, and contrast their physical properties. We describe localization properties using a locator expansion on general lattices. For 1d Ising chains, we find non-analytic behavior of the localization length as a function of energy at ?=0, ?{sup ?1}(?)=?{sup ?1}(0)+A|?|{sup ?}, with ? vanishing at criticality. This contrasts with the much smoother behavior predicted for XY magnets. We use these results to approach the ordering transition on Bethe lattices of large connectivity K, which mimic the limit of high dimensionality. In both models, in the paramagnetic phase with uniform disorder, the localization length is found to have a local maximum at ?=0. For the Ising model, we find activated scaling at the phase transition, in agreement with infinite randomness studies. In the Ising model long range order is found to arise due to a delocalization and condensation initiated at ?=0, without a closing mobility gap. We find that Ising systems establish order on much sparser (fractal) subgraphs than XY models. Possible implications of these results for finite-dimensional systems are discussed. -- Highlights: •Study of localization properties of disordered bosons and spins in random fields. •Comparison between XY magnets (hard-core bosons) and Ising magnets. •Analysis of the nature of the magnetic transition in strong quenched disorder. •Ising magnets: activated scaling, no closing mobility gap at the transition. •Ising order emerges on sparser (fractal) support than XY order.

  12. Design of the Local Spin Polarization at the Organic-Ferromagnetic Interface

    E-Print Network [OSTI]

    Lazic, Predrag

    By means of ab initio calculations and spin-polarized scanning tunneling microscopy experiments the creation of a complex energy dependent magnetic structure with a tailored spin-polarized interface is demonstrated. We ...

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

    SciTech Connect (OSTI)

    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

    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.

  14. Spin transport in benzofurane bithiophene based organic spin valves

    SciTech Connect (OSTI)

    Palosse, Mathieu; Séguy, Isabelle; Bedel-Pereira, Élena [CNRS, LAAS, 7 avenue du Colonel Roche, F-31400 Toulouse (France) [CNRS, LAAS, 7 avenue du Colonel Roche, F-31400 Toulouse (France); Université de Toulouse (France); UPS, INSA, INP, ISAE (France); LAAS (France) [France; CEMES, F-31077 Toulouse (France)] [France; Villeneuve-Faure, Christina [Université de Toulouse (France) [Université de Toulouse (France); UPS, INSA, INP, ISAE (France); LAAS (France) [France; CEMES, F-31077 Toulouse (France) [France; LAPLACE, Université Paul Sabatier, 118, route de Narbonne 31062 Toulouse Cedex 9 (France); Mallet, Charlotte; Frère, Pierre [MOLTECH-Anjou, UMR CNRS 6200, Université d’Angers, 2 Bd Lavoisier 49045 ANGERS Cedex (France)] [MOLTECH-Anjou, UMR CNRS 6200, Université d’Angers, 2 Bd Lavoisier 49045 ANGERS Cedex (France); Warot-Fonrose, Bénédicte; Biziere, Nicolas [Université de Toulouse (France) [Université de Toulouse (France); UPS, INSA, INP, ISAE (France); LAAS (France) [France; CEMES, F-31077 Toulouse (France) [France; CNRS, CEMES-CNRS UPR 8011, 29 rue Jeanne Marvig, BP 94347, FR-31055 Toulouse Cedex 4 (France); Bobo, Jean-François, E-mail: jfbobo@cemes.fr [Université de Toulouse (France) [Université de Toulouse (France); UPS, INSA, INP, ISAE (France); LAAS (France) [France; CEMES, F-31077 Toulouse (France) [France; CNRS, CEMES-ONERA, NMH, 2 avenue Edouard Belin, FR-31055 Toulouse Cedex 4 (France)

    2014-01-15T23:59:59.000Z

    In this paper we present spin transport in organic spin-valves using benzofurane bithiophene (BF3) as spacer layer between NiFe and Co ferromagnetic electrodes. The use of an AlO{sub x} buffer layer between the top electrode and the organic layer is discussed in terms of improvements of stacking topology, electrical transport and oxygen contamination of the BF3 layer. A study of magnetic hysteresis cycles evidences spin-valve behaviour. Transport properties are indicative of unshorted devices with non-linear I-V characteristics. Finally we report a magnetoresistance of 3% at 40 K and 10 mV in a sample with a 50 nm thick spacer layer, using an AlO{sub x} buffer layer.

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

    SciTech Connect (OSTI)

    Lendinez, S. [Univ. de Barcelona, Barcelona, Spain (Europe); Billinge, S. J. L. [Columbia Univ., New York, NY (United States); Zarzuela, R. [Univ. de Barcelona, Barcelona, Spain (Europe); Tejada, J. [Univ. de Barcelona, Barcelona, Spain (Europe); Terban, M. W. [Columbia Univ., New York, NY (United States); Espin, J. [Univ. Autonoma Barcelona, Barcelona, Spain (Europe); Imaz, I. [Univ. Autonoma Barcelona, Barcelona, Spain (Europe); Maspoch, D. [Univ. Autonoma Barcelona, Barcelona, Spain (Europe); Chudnovsky, E. M. [City Univ. of New York, Bronx, NY (United States)

    2015-01-01T23:59:59.000Z

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

  16. JOURNAL DE PHYSIQUE Colloque C6, supplment au n 8, Tome 39, aot 1978, page C6-910 OBSERVATION OF MAGNETIZATION REVERSAL AND MACROSCOPIC MAGNETIC DOMAINS IN Cu. Mn SPIN

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    of the magnetic flux variation induced by the pas- sage of the sample between two counter-wounded pick up coils two measurements. The sample is in the form of a cylinder 0.5 x 0.5 x 2 cm. It has been made from high

  17. Spin rotation of polarized beams in high energy storage ring

    E-Print Network [OSTI]

    V. G. Baryshevsky

    2006-03-23T23:59:59.000Z

    The equations for spin evolution of a particle in a storage ring are obtained considering contributions from the tensor electric and magnetic polarizabilities of the particle along with the contributions from spin rotation and birefringence effect in polarized matter of an internal target. % Study of the spin rotation and birefringence effects for a particle in a high energy storage ring provides for measurement both the spin-dependent real part of the coherent elastic zero-angle scattering amplitude and tensor electric (magnetic) polarizabilities.

  18. Intrinsic Spin-Orbit Interaction in Graphene

    E-Print Network [OSTI]

    B. S. Kandemir

    2012-05-03T23:59:59.000Z

    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.

  19. Spin dynamics simulation of electron spin relaxation in Ni{sup 2+}(aq)

    SciTech Connect (OSTI)

    Rantaharju, Jyrki, E-mail: jjrantaharju@gmail.com; Mareš, Ji?í, E-mail: jiri.mares@oulu.fi; Vaara, Juha, E-mail: juha.vaara@iki.fi [NMR Research Group, Department of Physics, University of Oulu, P.O. Box 3000, Oulu, FIN-90014 (Finland)

    2014-07-07T23:59:59.000Z

    The ability to quantitatively predict and analyze the rate of electron spin relaxation of open-shell systems is important for electron paramagnetic resonance and paramagnetic nuclear magnetic resonance spectroscopies. We present a combined molecular dynamics (MD), quantum chemistry (QC), and spin dynamics simulation method for calculating such spin relaxation rates. The method is based on the sampling of a MD trajectory by QC calculations, to produce instantaneous parameters of the spin Hamiltonian used, in turn, to numerically solve the Liouville-von Neumann equation for the time evolution of the spin density matrix. We demonstrate the approach by simulating the relaxation of electron spin in an aqueous solution of Ni{sup 2+} ion. The spin-lattice (T{sub 1}) and spin-spin (T{sub 2}) relaxation rates are extracted directly from the simulations of the time dependence of the longitudinal and transverse magnetization, respectively. Good agreement with the available, indirectly obtained experimental data is obtained by our method.

  20. Evidence for spin glass state of NdCo{sub 1?x}Ni{sub x}O{sub 3} (x?=?0.3?0.5)

    SciTech Connect (OSTI)

    Kumar, Vinod, E-mail: kumarvinodphy@gmail.com; Kumar, Rajesh [Department of Physics, National Institute of Technology, Hamirpur, Himachal Pradesh 177 005 (India); Singh, Kiran [Tata Institute of Fundamental Research, HomiBhaba Road, Colaba Mumbai-400005 (India); Arora, S. K.; Shvets, I. V. [CRANN, School of Physics, Trinity College Dublin, Dublin 2, Republic of Ireland (Ireland); Kumar, Ravi [Centre for Materials Science and Engineering, National Institute of Technology, Hamirpur, Himachal Pradesh 177 005 (India)

    2014-08-21T23:59:59.000Z

    Low-temperature magnetic properties of single phase NdCo{sub 1?x}Ni{sub x}O{sub 3}(x?=?0.3?0.5) have been studied using ac and dc magnetic susceptibility measurements. Nickel substituted samples have been found to exhibit a different magnetic state at low temperature as compared to pristine NdCoO{sub 3}. The temperature dependent dc magnetization M (T) revealed the presence of a sharp cusp occurring at characteristic temperatures T{sub P}, for x?=?0.3, 0.4, 0.5. Below T{sub P}, clear effect of magnetic field can be seen in M (T) curves and T{sub P} decreases with increasing magnetic field as well as Ni substitution content. The isothermal magnetization measurements at low temperatures shows small unsaturated hysteresis loop at lowest temperature (10?K). The ac susceptibility results show a clear frequency dependent feature. These results are analyzed to distinguish superparamagnetic and spin glass behavior by using Néel-Arrhennius, Vogel-Fulcher law, and power law fitting. This analysis ruled out the superparamagnet like state and suggests the presence of significant inter-cluster interactions, giving rise to spin-glass like cooperative freezing.

  1. Bruker BioSpin EPR (Electron Paramagnetic Resonance) is a spectroscopic

    E-Print Network [OSTI]

    Niebur, Ernst

    might put on your refrigerator. When we supply an external magnetic field, the paramagnetic electrons is a magnetic resonance technique very similar to NMR (Nuclear Magnetic Resonance). However, instead in an applied magnetic field. Like a proton, the electron has "spin", which gives it a magnetic property known

  2. Demand Response Spinning Reserve Demonstration

    E-Print Network [OSTI]

    2007-01-01T23:59:59.000Z

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

  3. Magneto-transport through single-molecule magnets: Kondo-peaks, zero-bias dips, molecular symmetry and Berry's phase

    E-Print Network [OSTI]

    and conditions apply. View the table of contents for this issue, or go to the journal homepage for more Home smaller, see [2], and the re-entrant behavior of the New Journal of Physics 13 (2011) 079501 1367 , and the magnetic field energy Hx in units of the diabolical scale H x = 2B2(D + B2) for half-integer spin S = 3

  4. Electron spin decoherence in isotope-enriched silicon

    E-Print Network [OSTI]

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

    2010-10-27T23:59:59.000Z

    Silicon is promising for spin-based quantum computation because nuclear spins, a source of magnetic noise, may be eliminated through isotopic enrichment. Long spin decoherence times, $T_2$, have been measured in isotope-enriched silicon but come far short of the $T_2 = 2 T_1$ limit. The effect of nuclear spins on $T_2$ is well established. However, the effect of background electron spins from ever present residual phosphorus impurities in silicon can also produce significant decoherence. We study spin decoherence decay as a function of donor concentration, $^{29}$Si concentration, and temperature using cluster expansion techniques specifically adapted to the problem of a sparse dipolarly coupled electron spin bath. Our results agree with the existing experimental spin echo data in Si:P and establish the importance of background dopants as the ultimate decoherence mechanism in isotope-enriched silicon.

  5. Coherent Control of a Single Silicon-29 Nuclear Spin Qubit

    E-Print Network [OSTI]

    Jarryd J. Pla; Fahd A. Mohiyaddin; Kuan Y. Tan; Juan P. Dehollain; Rajib Rahman; Gerhard Klimeck; David N. Jamieson; Andrew S. Dzurak; Andrea Morello

    2014-08-06T23:59:59.000Z

    Magnetic fluctuations caused by the nuclear spins of a host crystal are often the leading source of decoherence for many types of solid-state spin qubit. In group-IV materials, the spin-bearing nuclei are sufficiently rare that it is possible to identify and control individual host nuclear spins. This work presents the first experimental detection and manipulation of a single $^{29}$Si nuclear spin. The quantum non-demolition (QND) single-shot readout of the spin is demonstrated, and a Hahn echo measurement reveals a coherence time of $T_2 = 6.3(7)$ ms - in excellent agreement with bulk experiments. Atomistic modeling combined with extracted experimental parameters provides possible lattice sites for the $^{29}$Si atom under investigation. These results demonstrate that single $^{29}$Si nuclear spins could serve as a valuable resource in a silicon spin-based quantum computer.

  6. Understanding magnetic field reversal mechanisms in mesoscopic magnetic multilayer ring structures

    E-Print Network [OSTI]

    Ng, Bryan

    2008-01-01T23:59:59.000Z

    Patterned pseudo spin-valve rings show great promise for device applications due to their non-volatility and variety of stable magnetic states. However, the magnetic reversal of these elements under an applied field is ...

  7. Environment Assisted Metrology with Spin Qubit

    E-Print Network [OSTI]

    P. Cappellaro; G. Goldstein; J. S. Hodges; L. Jiang; J. R. Maze; A. S. Sørensen; M. D. Lukin

    2012-01-12T23:59:59.000Z

    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.

  8. Unexpected magnetization enhancement in hydrogen plasma treated ferromagnetic (Zn,Cu)O film

    SciTech Connect (OSTI)

    Hu, Liang; Zhu, Liping, E-mail: zlp1@zju.edu.cn, E-mail: hphe@zju.edu.cn; He, Haiping, E-mail: zlp1@zju.edu.cn, E-mail: hphe@zju.edu.cn; Ye, Zhizhen [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China and Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027 (China)

    2014-08-18T23:59:59.000Z

    The effects of H{sup +} incorporation on oxygen vacancies (H{sub O}{sup +}) on the giant ferromagnetic behavior (moment up to 3.26??{sub B}/Cu) in ZnO:Cu polycrystalline films have been closely examined using different microstructural and magnetic characterization tools. Fine thermal stability (up to 450?°C) and low resistivity demonstrate a significant correlation between Cu 3d-states and H{sub O}{sup +} donor defects in H plasma treated ZnO:Cu films, analogous to dual-donor (V{sub O} and Zn{sub i}) defects mediated case. These H{sub O}{sup +} donors can delocalize their electrons to the orbits of Cu atoms and contribute to a stronger spin-orbit coupling interaction. Suitable H{sub O}{sup +} defect concentration and matched proportion between Cu{sup 2+} and Cu{sup +} species ensure that orbital momentum shall not be quenched. Hence, unexpected moment enhancement, less than spin-orbit coupling upper limit (3.55??{sub B}/Cu), can be also expected in this scenario. The manipulation from spin-only to spin-orbit coupling mode, using a facile thermally-mediated H plasma exposure way, will allow achieving spin transport based diluted magnetic semiconductor device.

  9. Exact diagonalization for spin-1/2 chains and the first order quantum phase transitions of the XXX chain in a uniform transverse field

    E-Print Network [OSTI]

    Feng Pan; Xin Guan; Nan Ma; Wen-Juan Han; J. P. Draayer

    2007-02-04T23:59:59.000Z

    A simple Mathematica code based on the differential realization of hard-core boson operators for finding exact solutions of the periodic-N spin-1/2 systems with or beyond nearest neighbor interactions is proposed, which can easily be used to study general spin-1/2 interaction systems. As an example, The code is applied to study XXX spin-1/2 chain with nearest neighbor interaction in a uniform transverse field. It shows that there are [N/2] level-crossing points in the ground state, where N is the periodic number of the system and [x] stands for the integer part of x, when the interaction strength and magnitude of the magnetic field satisfy certain conditions. The quantum phase transitional behavior in the ground state of the system in the thermodynamic limit is also studied.

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

    E-Print Network [OSTI]

    Banasri Basu; Pratul Bandyopadhyay; Priyadarshi Majumdar

    2011-03-07T23:59:59.000Z

    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.

  11. 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)

    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

    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.

  12. Magnetohydrodynamic spin waves in degenerate electron-positron-ion plasmas

    SciTech Connect (OSTI)

    Mushtaq, A. [TPPD, PINSTECH Nilore, 44000 Islamabad (Pakistan); National Center for Physics, Shahdrah Valley Road, 44000 Islamabad (Pakistan); Maroof, R.; Ahmad, Zulfiaqr [Institute of Physics and Electronics, University of Peshawar, 25000 Peshawar (Pakistan); Qamar, A. [National Center for Physics, Shahdrah Valley Road, 44000 Islamabad (Pakistan); Institute of Physics and Electronics, University of Peshawar, 25000 Peshawar (Pakistan)

    2012-05-15T23:59:59.000Z

    Low frequency magnetosonic waves are studied in magnetized degenerate electron-positron-ion plasmas with spin effects. Using the fluid equations of magnetoplasma with quantum corrections due to the Bohm potential, temperature degeneracy, and spin magnetization energy, a generalized dispersion relation for oblique magnetosonic waves is derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. For three different values of angle {theta}, the generalized dispersion relation is reduced to three different relations under the low frequency magnetohydrodynamic assumptions. It is found that the effect of quantum corrections in the presence of positron concentration significantly modifies the dispersive properties of these modes. The importance of the work relevant to compact astrophysical bodies is pointed out.

  13. Proximity effects in superconducting triplet spin-valve F2/F1/S R.G. Deminov a,n

    E-Print Network [OSTI]

    Fominov, Yakov

    Proximity effects in superconducting triplet spin-valve F2/F1/S R.G. Deminov a,n , L.R. Tagirov a effect Superconducting Ferromagnetic Triplet spin-valve Magnetization Transition temperature Interface of the spin-valve effect mode selection (standard switching effect, the triplet spin-valve effect or reentrant

  14. angle field spinning: Topics by E-print Network

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

    and Glitches Astrophysics (arXiv) Summary: In the core of a canonical spinning magnetized neutron star(NS) a nearly uniform superfluid neutron vortex-array interacts strongly with...

  15. Spin properties of very shallow nitrogen vacancy defects in diamond

    E-Print Network [OSTI]

    Ofori-Okai, Benjamin Kwasi

    We investigate spin and optical properties of individual nitrogen vacancy centers located within 1–10 nm from the diamond surface. We observe stable defects with a characteristic optically detected magnetic-resonance ...

  16. Calculating the spontaneous magnetization and defining the Curie temperature using a positive-feedback model

    SciTech Connect (OSTI)

    Harrison, R. G., E-mail: rgh@doe.carleton.ca [Department of Electronics, Carleton University, Ottawa, Ontario K1S 5B6 (Canada)

    2014-01-21T23:59:59.000Z

    A positive-feedback mean-field modification of the classical Brillouin magnetization theory provides an explanation of the apparent persistence of the spontaneous magnetization beyond the conventional Curie temperature—the little understood “tail” phenomenon that occurs in many ferromagnetic materials. The classical theory is unable to resolve this apparent anomaly. The modified theory incorporates the temperature-dependent quantum-scale hysteretic and mesoscopic domain-scale anhysteretic magnetization processes and includes the effects of demagnetizing and exchange fields. It is found that the thermal behavior of the reversible and irreversible segments of the hysteresis loops, as predicted by the theory, is a key to the presence or absence of the “tails.” The theory, which permits arbitrary values of the quantum spin number J, generally provides a quantitative agreement with the thermal variations of both the spontaneous magnetization and the shape of the hysteresis loop.

  17. Spin Entanglement of Two delocalised Fermions and Berry Phase

    E-Print Network [OSTI]

    B. Basu; P. Bandyopadhyay

    2007-12-26T23:59:59.000Z

    We have studied the entanglement of identical fermions in two spatial regions in terms of the Berry phase acquired by their spins. The analysis is done from the viewpoint of the geometrical interpretation of entanglement, where a fermion is visualized as a scalar particle attached with a magnetic flux quantum. The quantification of spin entanglement in terms of their Berry phases is novel and generalises the relationship between the entanglement of distinguishable spins and that of delocalised fermions.

  18. Nanopillar Spin Filter Tunnel Junctions with Manganite Barriers

    E-Print Network [OSTI]

    Prasad, Bhagwati; Egilmez, Mehmet; Schoofs, Frank; Fix, Thomas; Vickers, Mary E; Zhang, Wenrui; Jian, Jie; Wang, Haiyan; Blamire, Mark G

    2014-04-17T23:59:59.000Z

    of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS, UK ‡ Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, 77843-3128, USA KEYWORDS: Spin filter, Nano... magnetic memories, reprogrammable logic and quantum computers.1,2 These devices rely on the generation of highly spin-polarized currents. Spin filter tunnel junction (SFTJ) has emerged as a promising alternative for this purpose. A possible way...

  19. Electric control of magnetization relaxation in thin film magnetic insulators.

    SciTech Connect (OSTI)

    Wang, Z.; Sun, Y.; Song, Y-Y.; Wu, M.; Schultheiss, H.; Pearson, J. E.; Hoffmann, A. (Materials Science Division); (Colorado State Univ.)

    2011-10-01T23:59:59.000Z

    Control of magnetization relaxation in magnetic insulators via interfacial spin scattering is demonstrated. The experiments use nanometer-thick yttrium iron garnet (YIG)/Pt layered structures, with the Pt layer biased by an electric voltage. The bias voltage produces a spin current across the Pt thickness. As this current scatters off the YIG surface, it exerts a torque on the YIG surface spins. This torque can reduce or enhance the damping and thereby decrease or increase the ferromagnetic resonance linewidth of the YIG film, depending on the field/current configuration.

  20. Tidal deformations of a spinning compact object

    E-Print Network [OSTI]

    Paolo Pani; Leonardo Gualtieri; Andrea Maselli; Valeria Ferrari

    2015-03-25T23:59:59.000Z

    The deformability of a compact object induced by a perturbing tidal field is encoded in the tidal Love numbers, which depend sensibly on the object's internal structure. These numbers are known only for static, spherically-symmetric objects. As a first step to compute the tidal Love numbers of a spinning compact star, here we extend powerful perturbative techniques to compute the exterior geometry of a spinning object distorted by an axisymmetric tidal field to second order in the angular momentum. The spin of the object introduces couplings between electric and magnetic deformations and new classes of induced Love numbers emerge. For example, a spinning object immersed in a quadrupolar, electric tidal field can acquire some induced mass, spin, quadrupole, octupole and hexadecapole moments to second order in the spin. The deformations are encoded in a set of inhomogeneous differential equations which, remarkably, can be solved analytically in vacuum. We discuss certain subtleties in defining the multipole moments of the central object, which are due to the difficulty in separating the tidal field from the linear response of the object in the solution. By extending the standard procedure to identify the linear response in the static case, we prove analytically that the Love numbers of a Kerr black hole remain zero to second order in the spin. As a by-product, we provide the explicit form for a slowly-rotating, tidally-deformed Kerr black hole to quadratic order in the spin, and discuss its geodesic and geometrical properties.

  1. Quantum Phase Transition in Dimerized Spin-1/2 Chains

    E-Print Network [OSTI]

    Aparajita Das; Sreeparna Bhadra; Sonali Saha

    2015-03-30T23:59:59.000Z

    Quantum phase transition in dimerized antiferromagnetic Heisenberg spin chain has been studied. A staircase structure in the variation of concurrence within strongly coupled pairs with that of external magnetic field has been observed indicating multiple critical points. Emergence of entanglement due to external magnetic field or magnetic entanglement is observed for weakly coupled spin pairs in the same dimer chain. Though closed dimerized isotropic XXX Heisenberg chains with different dimer strengths were mainly explored, analogous studies on open chains as well as closed anisotropic (XX interaction) chains with tilted external magnetic field have also been studied.

  2. Conductance of ferro- and antiferro-magnetic single-atom contacts: A first-principles study

    SciTech Connect (OSTI)

    Tan, Zhi-Yun [School of Physics and Mechanical and Electrical Engineering, Zunyi Normal College, Zunyi (China)] [School of Physics and Mechanical and Electrical Engineering, Zunyi Normal College, Zunyi (China); Zheng, Xiao-long; Ye, Xiang; Xie, Yi-qun [Department of Physics, Shanghai Normal University, 100 Guilin Road, Shanghai 200232 (China)] [Department of Physics, Shanghai Normal University, 100 Guilin Road, Shanghai 200232 (China); Ke, San-Huang [Department of Physics, Key Laboratory of Advanced Microstructured Materials, MOE, Tongji University, 1239 Siping Road, Shanghai 200092 (China)] [Department of Physics, Key Laboratory of Advanced Microstructured Materials, MOE, Tongji University, 1239 Siping Road, Shanghai 200092 (China)

    2013-08-14T23:59:59.000Z

    We present a first-principles study on the spin dependent conductance of five single-atom magnetic junctions consisting of a magnetic tip and an adatom adsorbed on a magnetic surface, i.e., the Co-Co/Co(001) and Ni-X/Ni(001) (X = Fe, Co, Ni, Cu) junctions. When their spin configuration changes from ferromagnetism to anti-ferromagnetism, the spin-up conductance increases while the spin-down one decreases. For the junctions with a magnetic adatom, there is nearly no spin valve effect as the decreased spin-down conductance counteracts the increased spin-up one. For the junction with a nonmagnetic adatom (Ni-Cu/Ni(001)), a spin valve effect is obtained with a variation of 22% in the total conductance. In addition, the change in spin configuration enhances the spin filter effect for the Ni-Fe/Ni(001) junction but suppresses it for the other junctions.

  3. Novel nuclear magnetic resonance techniques for studying biological molecules

    E-Print Network [OSTI]

    Laws, David D.

    2010-01-01T23:59:59.000Z

    parameters by solid-state nuclear magnetic resonance." J.and R. V. Pound. "Nuclear audiofrequency spectroscopy byresonant heating of the nuclear spin system." Phys. Rev. ,

  4. Chaotic Dynamics of Spin-Valve Oscillators Z. Yang and S. Zhang

    E-Print Network [OSTI]

    Li, Charles

    Chaotic Dynamics of Spin-Valve Oscillators Z. Yang and S. Zhang Department of Physics and Astronomy oscillators with tunable mi- crowave frequencies in spin valves are very desirable for magnetic storage it is not an intrinsic property of the current-driven oscillator. Here we consider a single-domain current-driven spin-valve

  5. A quantum Otto engine with a spin-$1/2$ and an arbitrary spin coupled by Heisenberg exchange

    E-Print Network [OSTI]

    Ferdi Altintas; Özgür E. Müstecapl?o?lu

    2015-02-26T23:59:59.000Z

    We investigate a quantum heat engine with a working substance of two particles, one with a spin-$1/2$ and the other with an arbitrary spin (spin-$s$), coupled by Heisenberg exchange interaction, and subject to an external magnetic field. The engine operates in a quantum Otto cycle. Work harvested in the cycle and its efficiency are calculated using quantum thermodynamical definitions. It is found that the engine has higher efficiencies at higher spin values and can harvest work at higher exchange interaction strengths.The role of exchange coupling and spin-$s$ on the work output and the thermal efficiency is studied in detail. In addition, the engine operation is analyzed from the perspective of local work and efficiency. The local work definition is generalized for the global changes and the conditions when the global work can be equal or more than the sum of the local works are determined.

  6. Multiple-spin coherence transfer in linear Ising spin chains and beyond: numerically-optimized pulses and experiments

    E-Print Network [OSTI]

    Nimbalkar, Manoj; Neves, Jorge L; Elavarasi, S Begam; Yuan, Haidong; Khaneja, Navin; Dorai, Kavita; Glaser, Steffen J

    2011-01-01T23:59:59.000Z

    We study multiple-spin coherence transfers in linear Ising spin chains with nearest neighbor couplings. These constitute a model for efficient information transfers in future quantum computing devices and for many multi-dimensional experiments for the assignment of complex spectra in nuclear magnetic resonance spectroscopy. We complement prior analytic techniques for multiple-spin coherence transfers with a systematic numerical study where we obtain strong evidence that a certain analytically-motivated family of restricted controls is sufficient for time-optimality. In the case of a linear three-spin system, additional evidence suggests that prior analytic pulse sequences using this family of restricted controls are time-optimal even for arbitrary local controls. In addition, we compare the pulse sequences for linear Ising spin chains to pulse sequences for more realistic spin systems with additional long-range couplings between non-adjacent spins. We experimentally implement the derived pulse sequences in th...

  7. Reduced matrix elements of spin–spin interactions for the atomic f-electron configurations

    SciTech Connect (OSTI)

    Yeung, Y.Y., E-mail: yeungy@acm.org

    2014-03-15T23:59:59.000Z

    A re-examination of some major references on the intra-atomic magnetic interactions over the last six decades reveals that there exist some gaps or puzzles concerning the previous studies of the spin–spin interactions for the atomic f-shell electrons. Hence, tables are provided for the relevant reduced matrix elements of the four double-tensor operators z{sub r} (r=1,2,3, and 4) of rank 2 in both the orbital and spin spaces. The range of the tables covers all states of the configurations from f{sup 4} to f{sup 7}.

  8. Viewing spin structures with soft x-ray microscopy

    SciTech Connect (OSTI)

    Fischer, Peter

    2010-06-01T23:59:59.000Z

    The spin of the electron and its associated magnetic moment marks the basic unit for magnetic properties of matter. Magnetism, in particular ferromagnetism and antiferromagnetism is described by a collective order of these spins, where the interaction between individual spins reflects a competition between exchange, anisotropy and dipolar energy terms. As a result the energetically favored ground state of a ferromagnetic system is a rather complex spin configuration, the magnetic domain structure. Magnetism is one of the eldest scientific phenomena, yet it is one of the most powerful and versatile utilized physical effects in modern technologies, such as in magnetic storage and sensor devices. To achieve highest storage density, the relevant length scales, such as the bit size in disk drives is now approaching the nanoscale and as such further developments have to deal with nanoscience phenomena. Advanced characterization tools are required to fully understand the underlying physical principles. Magnetic microscopes using polarized soft X-rays offer a close-up view into magnetism with unique features, these include elemental sensitivity due to X-ray magnetic dichroism effects as contrast mechanism, high spatial resolution provided by state-of-the-art X-ray optics and fast time resolution limited by the inherent time structure of current X-ray sources, which will be overcome with the introduction of ultrafast and high brilliant X-ray sources.

  9. Superconductivity and Magnetism: Materials Properties

    E-Print Network [OSTI]

    .g. within high-Tc superconductivity, magnetic superconductors, MgB2, CMR materials, nanomagnetism and spin#12;#12;Superconductivity and Magnetism: Materials Properties and Developments #12;Copyright 2003 Risø National Laboratory Roskilde, Denmark ISBN 87-550-3244-3 ISSN 0907-0079 #12;Superconductivity

  10. Magnetic metallic multilayers

    SciTech Connect (OSTI)

    Hood, R.Q.

    1994-04-01T23:59:59.000Z

    Utilizing self-consistent Hartree-Fock calculations, several aspects of multilayers and interfaces are explored: enhancement and reduction of the local magnetic moments, magnetic coupling at the interfaces, magnetic arrangements within each film and among non-neighboring films, global symmetry of the systems, frustration, orientation of the various moments with respect to an outside applied field, and magnetic-field induced transitions. Magnetoresistance of ferromagnetic-normal-metal multilayers is found by solving the Boltzmann equation. Results explain the giant negative magnetoresistance encountered in these systems when an initial antiparallel arrangement is changed into a parallel configuration by an external magnetic field. The calculation depends on (1) geometric parameters (thicknesses of layers), (2) intrinsic metal parameters (number of conduction electrons, magnetization, and effective masses in layers), (3) bulk sample properties (conductivity relaxation times), (4) interface scattering properties (diffuse scattering versus potential scattering at the interfaces, and (5) outer surface scattering properties (specular versus diffuse surface scattering). It is found that a large negative magnetoresistance requires considerable asymmetry in interface scattering for the two spin orientations. Features of the interfaces that may produce an asymmetrical spin-dependent scattering are studied: varying interfacial geometric random roughness with no lateral coherence, correlated (quasi-periodic) roughness, and varying chemical composition of the interfaces. The interplay between these aspects of the interfaces may enhance or suppress the magnetoresistance, depending on whether it increases or decreases the asymmetry in the spin-dependent scattering of the conduction electrons.

  11. Optimization of spin-torque switching using AC and DC pulses

    SciTech Connect (OSTI)

    Dunn, Tom [Department of Physics, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Kamenev, Alex [Department of Physics, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2014-06-21T23:59:59.000Z

    We explore spin-torque induced magnetic reversal in magnetic tunnel junctions using combined AC and DC spin-current pulses. We calculate the optimal pulse times and current strengths for both AC and DC pulses as well as the optimal AC signal frequency, needed to minimize the Joule heat lost during the switching process. The results of this optimization are compared against numeric simulations. Finally, we show how this optimization leads to different dynamic regimes, where switching is optimized by either a purely AC or DC spin-current, or a combination AC/DC spin-current, depending on the anisotropy energies and the spin-current polarization.

  12. NMR relaxation in spin ice due to diffusing emergent monopoles I Christopher L. Henley

    E-Print Network [OSTI]

    Henley, Christopher L.

    out, or the reverse, which were shown to behave as (emergent) magnetic monopole [3]. The low, spin dynamics in ideal spin ice is due mainly to dilute, thermally excited magnetic monopole exponent in that exponential and the formulas for the T1 (longitudinal) and T2 (dephasing) relaxations

  13. PHYSICAL REVIEW B 85, 085117 (2012) Spin thermopower in interacting quantum dots

    E-Print Network [OSTI]

    Ramsak, Anton

    2012-01-01T23:59:59.000Z

    renormalization group method, we investigate the spin thermopower of a quantum dot in a magnetic field, the dependence of the spin-Seebeck coefficient on the temperature and the magnetic field is explained in terms applications, including power generation, refrigeration, and temperature measurement.1 Thermoelectric phenomena

  14. JOURNAL DE PHYSIQUE Colloque CS,suppltfmentau n" 6, Tome 41, juin 1980,page ~ 5 -2 4 1 SPIN-DEPENDENT RAMAN SCATTERING FROM PHONONS I N MAGNETIC SEMICONDUCTORS AND INSULATORS

    E-Print Network [OSTI]

    Boyer, Edmond

    -DEPENDENT RAMAN SCATTERING FROM PHONONS I N MAGNETIC SEMICONDUCTORS AND INSULATORS + ++G. Giintherodt, R. Merlin

  15. Studies of Optically Induced Magnetization Dynamics in Colloidal Iron Oxide Nanocrystals 

    E-Print Network [OSTI]

    Hsia, Chih-Hao

    2011-10-21T23:59:59.000Z

    on the correlation between the nanocrystal size and the rates of spin-lattice relaxation (SLR), a magnetization relaxation pathway, in magnetic nanocrystals. The size-dependent magnetization relaxation rate after optically induced demagnetization in colloidal Fe3O4...

  16. Studies of Optically Induced Magnetization Dynamics in Colloidal Iron Oxide Nanocrystals

    E-Print Network [OSTI]

    Hsia, Chih-Hao

    2011-10-21T23:59:59.000Z

    on the correlation between the nanocrystal size and the rates of spin-lattice relaxation (SLR), a magnetization relaxation pathway, in magnetic nanocrystals. The size-dependent magnetization relaxation rate after optically induced demagnetization in colloidal Fe3O4...

  17. Spin–glass transition in La{sub 0.75}Sr{sub 0.25}Mn{sub 0.5}Cr{sub 0.5?x}Al{sub x}O{sub 3??} perovskites

    SciTech Connect (OSTI)

    Azad, Abul K., E-mail: aka7@st-andrews.ac.uk [School of Chemistry, University of St. Andrews, Fife KY16 9ST (United Kingdom); Sanchez-Benitez, Javier [Centre for Science at Extreme Conditions, University of Edinburgh, Erskine Building, Edinburgh EH9 3JZ (United Kingdom); Irvine, John T.S. [School of Chemistry, University of St. Andrews, Fife KY16 9ST (United Kingdom)

    2013-07-15T23:59:59.000Z

    Graphical abstract: In-phase and out-of-phase ac susceptibility measurements at the magnetic field 1000 Oe show the shifting of transition temperature with frequency (i.e. spin–glass transition) in La{sub 0.75}Sr{sub 0.25}Mn{sub 0.5}Cr{sub 0.3}Al{sub 0.2}O{sub 3??}. - Highlights: • Spin–glass transition at low temperature (around 50 K). • Al-doping decreases the antiferromagnetic transition temperature. • Ferromagnetic around room temperature. - Abstract: The structural and magnetic properties of the Al-doped La{sub 0.75}Sr{sub 0.25}Mn{sub 0.5}Cr{sub 0.5?x}Al{sub x}O{sub 3??} (x = 0.0, 0.1, 0.2, 0.3) were investigated by X-ray powder diffraction, neutron powder diffraction and magnetization measurements. Rietveld refinement of the diffraction data confirms that the compounds crystallize in rhombohedral symmetry (space group, R-3C). Unit cell volume decreases with increasing concentration of Al at the B-site. Upon cooling from room temperature, we have observed multiple magnetic phase transitions, i.e. paramagnetic (PM), ferromagnetic (FM), antiferromagnetic (AFM) and spin–glass (SG), in the samples. A low temperature magnetic hysteresis study demonstrates the presence of ferromagnetic domains for all compositions. The antiferromagnetic transition temperature decreases with the Al-doping AC susceptibility measurements at 97 Hz and 1 Oe show SG behaviors with a spin-freezing temperature close to 50 K for all samples. The in-phase ac susceptibility (?{sup /}) decreases in magnitude and spin–glass transition (T{sub SG}) increase toward higher temperature with increasing frequency. The spin–glass behavior accompanied by the anomalous magnetic transitions is due to the competing interactions between FM and AFM. The results also shows that a part of the samples lose magnetic order to form a SG state accompanied by an AFM state at low temperature.

  18. Thermal entanglement properties of small spin clusters

    SciTech Connect (OSTI)

    Bose, Indrani; Tribedi, Amit [Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata 700 009 (India)

    2005-08-15T23:59:59.000Z

    Exchange interactions in spin systems can give rise to quantum entanglement in the ground and thermal states of the systems. We consider a spin tetramer, with spins of magnitude (1/2), in which the spins interact via nearest-neighbor, diagonal, and four-spin interactions of strength J{sub 1}, J{sub 2}, and K, respectively. The ground- and thermal-state entanglement properties of the tetramer are calculated analytically in the various limiting cases. Both bipartite and multipartite entanglements are considered and a signature of the quantum phase transition (QPT), in terms of the entanglement ratio, is identified. The first-order QPT is accompanied by discontinuities in the nearest-neighbor and diagonal concurrences. The magnetic properties of a S=(1/2) antiferromagnetic polyoxovanadate compound V12 are well explained by tetramers, with J{sub 2}=0, K=0, in which the spins interact via the isotropic Heisenberg exchange interaction Hamiltonian. Treating the magnetic susceptibility {chi} as an entanglement witness (EW), an estimate of the lower bound of the critical entanglement temperature T{sub c} below which entanglement is present in the experimental compound, is determined. Two other cases considered include the symmetric tetramer--i.e., tetrahedron (J{sub 1}=J{sub 2},K=0)--and the symmetric trimer. In both the cases, there is no entanglement between a pair of spins in the thermal state but multipartite entanglement is present. A second EW based on energy provides an estimate of the entanglement temperature T{sub E} below which the thermal state is definitely entangled. This EW detects bipartite entanglement in the case of the tetramer describing a square of spins (the case of V12 ) and multipartite entanglement in the cases of the tetrahedron and symmetric trimer.

  19. Spin contribution to the ponderomotive force in a plasma

    E-Print Network [OSTI]

    G. Brodin; A. P. Misra; M. Marklund

    2010-07-30T23:59:59.000Z

    The concept of a ponderomotive force due to the intrinsic spin of electrons is developed. An expression containing both the classical as well as the spin-induced ponderomotive force is derived. The results are used to demonstrate that an electromagnetic pulse can induce a spin-polarized plasma. Furthermore, it is shown that for certain parameters, the nonlinear back-reaction on the electromagnetic pulse from the spin magnetization current can be larger than that from the classical free current. Suitable parameter values for a direct test of this effect are presented.

  20. Spin noise spectroscopy beyond thermal equilibrium and linear response

    E-Print Network [OSTI]

    P. Glasenapp; Luyi Yang; D. Roy; D. G. Rickel; A. Greilich; M. Bayer; N. A. Sinitsyn; S. A. Crooker

    2014-07-10T23:59:59.000Z

    Per the fluctuation-dissipation theorem, the information obtained from spin fluctuation studies in thermal equilibrium is necessarily constrained by the system's linear response functions. However, by including weak radiofrequency magnetic fields, we demonstrate that intrinsic and random spin fluctuations even in strictly unpolarized ensembles \\emph{can} reveal underlying patterns of correlation and coupling beyond linear response, and can be used to study non-equilibrium and even multiphoton coherent spin phenomena. We demonstrate this capability in a classical vapor of $^{41}$K alkali atoms, where spin fluctuations alone directly reveal Rabi splittings, the formation of Mollow triplets and Autler-Townes doublets, ac Zeeman shifts, and even nonlinear multiphoton coherences.

  1. Spin Contribution to the Ponderomotive Force in a Plasma

    SciTech Connect (OSTI)

    Brodin, G.; Misra, A. P.; Marklund, M. [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden)

    2010-09-03T23:59:59.000Z

    The concept of a ponderomotive force due to the intrinsic spin of electrons is developed. An expression containing both the classical as well as the spin-induced ponderomotive force is derived. The results are used to demonstrate that an electromagnetic pulse can induce a spin-polarized plasma. Furthermore, it is shown that, for certain parameters, the nonlinear backreaction on the electromagnetic pulse from the spin magnetization current can be larger than that from the classical free current. Suitable parameter values for a direct test of this effect are presented.

  2. Spin Rotation of Formalism for Spin Tracking

    SciTech Connect (OSTI)

    Luccio,A.

    2008-02-01T23:59:59.000Z

    The problem of which coefficients are adequate to correctly represent the spin rotation in vector spin tracking for polarized proton and deuteron beams in synchrotrons is here re-examined in the light of recent discussions. The main aim of this note is to show where some previous erroneous results originated and how to code spin rotation in a tracking code. Some analysis of a recent experiment is presented that confirm the correctness of the assumptions.

  3. Magnetism in Gd-W films

    SciTech Connect (OSTI)

    Gadioli, Giovana Z.; Rouxinol, Francisco P.; Gelamo, Rogerio V.; Santos, Adenilson O. dos; Cardoso, Lisandro P.; Bica de Moraes, Mario A. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, 13083-970 Campinas, Sao Paulo (Brazil)

    2008-05-01T23:59:59.000Z

    Vapor condensation techniques are useful to prepare magnetic alloys whose components have low or even negligible equilibrium mutual solubility. In this work, one of these techniques--sputtering--was used to obtain Gd{sub x}W{sub 1-x} alloys whose magnetic properties were investigated as a function of the Gd atomic concentration x. Gadolinium and various Gd-based alloys are promising materials for magnetic refrigeration and this was one of the motivations for this study. The Gd{sub x}-W{sub 1-x} films were sputter deposited from Gd and W targets with x ranging from 0 to 1 as determined by x-ray energy-dispersive spectroscopic analyses. X-ray diffraction patterns indicate that crystalline structures were formed at low and high Gd concentrations, while at intermediate concentrations, the films were amorphous. Magnetization measurements, performed as a function of temperature and with static and alternating applied fields, reveal a spin glasslike behavior in all the W-containing samples for temperatures below the freezing temperature T{sub f}. For low and intermediate Gd concentrations, and for T>T{sub f}, the films were paramagnetic, while a ferromagnetic phase was observed in the Gd-W alloy of the highest Gd content. The magnetocaloric effect was investigated from the magnetization isotherms M versus H, from which the isothermal magnetic entropy variation {delta}S{sub M} as a function of T, for the removal of an applied field of 50 kOe, was determined. It was observed that the maximum value of {delta}S{sub M} for each {delta}S{sub M} versus T curve and the temperature at which these maxima occur, are strongly dependent on x.

  4. Enhancement of nonlocal spin-valve signal using spin accumulation in local spin-valve configuration

    E-Print Network [OSTI]

    Otani, Yoshichika

    Enhancement of nonlocal spin-valve signal using spin accumulation in local spin-valve configuration) We propose a nonlocal spin-valve measurement combined with a local spin-valve structure to enlarge spin signal. The probe configuration consists of a lateral spin valve with three Ni­Fe wires bridged

  5. Magnetic Catalysis vs Magnetic Inhibition

    E-Print Network [OSTI]

    Kenji Fukushima; Yoshimasa Hidaka

    2012-09-06T23:59:59.000Z

    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.

  6. Most spin-1/2 transition-metal ions do have single ion anisotropy

    SciTech Connect (OSTI)

    Liu, Jia; Whangbo, Myung-Hwan, E-mail: hxiang@fudan.edu.cn, E-mail: mike-whangbo@ncsu.edu [Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695 (United States); Koo, Hyun-Joo [Department of Chemistry and Research Institute for Basic Sciences, Kyung Hee University, Seoul 130-701 (Korea, Republic of); Xiang, Hongjun, E-mail: hxiang@fudan.edu.cn, E-mail: mike-whangbo@ncsu.edu [Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200433 (China); Kremer, Reinhard K. [Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart (Germany)

    2014-09-28T23:59:59.000Z

    The cause for the preferred spin orientation in magnetic systems containing spin-1/2 transition-metal ions was explored by studying the origin of the easy-plane anisotropy of the spin-1/2 Cu{sup 2+} ions in CuCl{sub 2}·2H{sub 2}O, LiCuVO{sub 4}, CuCl{sub 2}, and CuBr{sub 2} on the basis of density functional theory and magnetic dipole-dipole energy calculations as well as a perturbation theory treatment of the spin-orbit coupling. We find that the spin orientation observed for these spin-1/2 ions is not caused by their anisotropic spin exchange interactions, nor by their magnetic dipole-dipole interactions, but by the spin-orbit coupling associated with their crystal-field split d-states. Our study also predicts in-plane anisotropy for the Cu{sup 2+} ions of Bi{sub 2}CuO{sub 4} and Li{sub 2}CuO{sub 2}. The results of our investigations dispel the mistaken belief that magnetic systems with spin-1/2 ions have no magnetic anisotropy induced by spin-orbit coupling.

  7. Spin transition in a four-coordinate iron oxide

    SciTech Connect (OSTI)

    Kawakami, T. [Nihon University, Tokyo; Sutou, S. [Nihon University, Tokyo; Hirama, H. [Nihon University, Tokyo; Sekiya, Y. [Nihon University, Tokyo; Makino, T. [Nihon University, Tokyo; Tsujimoto, Y. [Kyoto University, Japan; Kitada, A. [Kyoto University, Japan; Tassel, C. [Kyoto University, Japan; Kageyama, H. [Kyoto University, Japan; Yoshimura, K. [Kyoto University, Japan; Chen, Xingqiu [ORNL; Fu, Chong Long [ORNL; Okada, T. [University of Tokyo, Tokyo, Japan; Yagi, T. [University of Tokyo, Tokyo, Japan; Hayashi, N. [Kyoto University, Japan; Nasu, S. [Osaka University; Podloucky, R. [Institut fur Physikalische Chemie der RWTH; Takano, M. [Kyoto University, Japan

    2009-01-01T23:59:59.000Z

    The spin transition, or spin crossover, is a manifestation of electronic instability induced by external constraints such as pressure1. Among known examples that exhibit spin transition, 3d ions with d6 electron configurations represent the vast majority, but the spin transition observed thus far has been almost exclusively limited to that between high-spin (S = 2) and low-spin (S = 0) states2-9. Here we report a novel high-spin to intermediate-spin (S = 1) state transition at 33 GPa induced by pressurization of an antiferromagnetic insulator SrFeO2 with a square planar coordination10. The change in spin multiplicity brings to ferromagnetism as well as metallicity, yet keeping the ordering temperature far above ambient. First-principles calculations attribute the origin of the transition to the strong inlayer hybridization between Fe dx 2 -y 2 O p , leading to a pressure-induced electronic instability toward the depopulation of Fe dx 2 -y 2 O p antibonding states. Furthermore, the ferromagnetic S = 1 state is half-metallic due to the inception of half-occupied spin-down (dxz, dyz) degenerate states upon spin transition. These results highlight the square-planar coordinated iron oxides as a new class of magnetic and electric materials and provide new avenues toward realizing multi-functional sensors and data-storage devices.

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

    E-Print Network [OSTI]

    C. M. S. da Conceição; E. C. Marino

    2009-03-02T23:59:59.000Z

    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.

  9. Spin Seebeck power generators

    SciTech Connect (OSTI)

    Cahaya, Adam B.; Tretiakov, O. A. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Bauer, Gerrit E. W. [Institute for Materials Research and WPI-AIMR, Tohoku University, Sendai 980-8577 (Japan); Kavli Institute of NanoScience, TU Delft Lorentzweg 1, 2628 CJ Delft (Netherlands)

    2014-01-27T23:59:59.000Z

    We derive expressions for the efficiency and figure of merit of two spin caloritronic devices based on the spin Seebeck effect (SSE), i.e., the generation of spin currents by a temperature gradient. The inverse spin Hall effect is conventionally used to detect the SSE and offers advantages for large area applications. We also propose a device that converts spin current into electric one by means of a spin-valve detector, which scales favorably to small sizes and approaches a figure of merit of 0.5 at room temperature.

  10. Magnetic Edge States in Graphene

    E-Print Network [OSTI]

    Gabriela Murguia

    2010-08-29T23:59:59.000Z

    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.

  11. SPIN-TORQUE IN SYSTEMS WITH INHOMOGENEOUS MAGETIZATION

    SciTech Connect (OSTI)

    Zangwill, Andrew [Georgia Institute of Technology

    2013-04-23T23:59:59.000Z

    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.

  12. Estimation of spin-diffusion length from the magnitude of spin-current absorption: Multiterminal ferromagnetic/nonferromagnetic hybrid structures

    E-Print Network [OSTI]

    Otani, Yoshichika

    to large sample dimensions. The current perpendicular to plane CPP giant magnetoresistance measurements by the spacer thickness.5 This tech- nique is suitable for the N layer with magnetic or even non- magnetic of the difficulty in pre- paring a CPP device with the thickness of the N spacer as thick as the spin diffusion

  13. Level Structure of 103Ag at high spins

    E-Print Network [OSTI]

    S. Ray; N. S. Pattabiraman; Krishichayan; A. Chakraborty; S. Mukhopadhyay; S. S. Ghugre; S. N. Chintalapudi; A. K. Sinha; U. Garg; S. Zhu; B. Kharraja; D. Almehed

    2007-12-07T23:59:59.000Z

    High spin states in $^{103}$Ag were investigated with the Gammasphere array, using the $^{72}$Ge($^{35}$Cl,$2p2n$)$^{103}$Ag reaction at an incident beam energy of 135 MeV. A $\\Delta J$=1 sequence with predominantly magnetic transitions and two nearly-degenerate $\\Delta J=1$ doublet bands have been observed. The dipole band shows a decreasing trend in the $B(M1)$ strength as function of spin, a well established feature of magnetic bands. The nearly-degenerate band structures satisfy the three experimental signatures of chirality in the nuclei; however microscopic calculations are indicative of a magnetic phenomenon

  14. Coupling spin ensembles via superconducting flux qubits

    E-Print Network [OSTI]

    Yueyin Qiu; Wei Xiong; Lin Tian; J. Q. You

    2014-09-10T23:59:59.000Z

    We study a hybrid quantum system consisting of spin ensembles and superconducting flux qubits, where each spin ensemble is realized using the nitrogen-vacancy centers in a diamond crystal and the nearest-neighbor spin ensembles are effectively coupled via a flux qubit.We show that the coupling strengths between flux qubits and spin ensembles can reach the strong and even ultrastrong coupling regimes by either engineering the hybrid structure in advance or tuning the excitation frequencies of spin ensembles via external magnetic fields. When extending the hybrid structure to an array with equal coupling strengths, we find that in the strong-coupling regime, the hybrid array is reduced to a tight-binding model of a one-dimensional bosonic lattice. In the ultrastrong-coupling regime, it exhibits quasiparticle excitations separated from the ground state by an energy gap. Moreover, these quasiparticle excitations and the ground state are stable under a certain condition that is tunable via the external magnetic field. This may provide an experimentally accessible method to probe the instability of the system.

  15. Spin dynamics characterization in magnetic dots

    E-Print Network [OSTI]

    Mozaffari, Mohammad Reza; Esfarjani, Keivan

    2007-01-01T23:59:59.000Z

    J= 0.1 meV Frequency (JS) SDF J=0.6 meV Fig. 2. (Colorfrom diagonalization (SDF: J=1 eV) Frequency spectrum fromMagnon DOS for a circular dot SDF: J=0.6 meV N=1600 N=400 N=

  16. Manipulating topological states by imprinting non-collinear spin textures

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

    Streubel, Robert; Han, Luyang; Im, Mi -Young; Kronast, Florian; Rößler, Ulrich K.; Radu, Florin; Abrudan, Radu; Lin, Gungun; Schmidt, Oliver G.; Fischer, Peter; et al

    2015-03-05T23:59:59.000Z

    Topological magnetic states, such as chiral skyrmions, are of great scientific interest and show huge potential for novel spintronics applications, provided their topological charges can be fully controlled. So far skyrmionic textures have been observed in noncentrosymmetric crystalline materials with low symmetry and at low temperatures. We propose theoretically and demonstrate experimentally the design of spin textures with topological charge densities that can be tailored at ambient temperatures. Tuning the interlayer coupling in vertically stacked nanopatterned magnetic heterostructures, such as a model system of a Co/Pd multilayer coupled to Permalloy, the in-plane non-collinear spin texture of one layer can bemore »imprinted into the out-of-plane magnetised material. We observe distinct spin textures, e.g. vortices, magnetic swirls with tunable opening angle, donut states and skyrmion core configurations. We show that applying a small magnetic field, a reliable switching between topologically distinct textures can be achieved at remanence« less

  17. Spin waves throughout the Brillouin zone and magnetic exchange coupling in ferromagnetic metallic manganites La$_{1-x}$Ca$_{x}$MnO$_3$ ($x=0.25,0.30$)

    SciTech Connect (OSTI)

    Ye, Feng [ORNL; Dai, Pengcheng [ORNL; Fernandez-Baca, Jaime A [ORNL; Adroja, D. T. [ISIS Facility, Rutherford Appleton Laboratory; Perring, T. G. [ISIS Facility, Rutherford Appleton Laboratory; Tomioka, Y. [Correlated Electron Research Center (CERC), Japan; Tokura, Y. [University of Tokyo, Tokyo, Japan

    2007-01-01T23:59:59.000Z

    Using time-of-flight and triple-axis inelastic neutron spectroscopy, we determine spin wave excitations throughout the Brillouin zone for ferromagnetic manganites La$_{1-x}$Ca$_x$MnO$_3$ ($x=0.25,0.3$) 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$_{0.7}$Ca$_{0.3}$MnO$_3$ are considerable softened in all symmetry directions compared to that of La$_{0.75}$Ca$_{0.25}$MnO$_3$. 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.

  18. Spin waves throughout the Brillouin zone and magnetic exchange coupling in the ferromagnetic metallic manganites La1?xCaxMnO3 (x=0.25, 0.30)

    SciTech Connect (OSTI)

    Ye, Feng [ORNL; Dai, Pengcheng [ORNL; Fernandez-Baca, Jaime A [ORNL; Adroja, D. T. [ISIS Facility, Rutherford Appleton Laboratory; Perring, T. G. [ISIS Facility, Rutherford Appleton Laboratory; Tomioka, Y. [Correlated Electron Research Center (CERC), Japan; Tokura, Y. [University of Tokyo, Tokyo, Japan

    2007-01-01T23:59:59.000Z

    Using time-of-flight and triple-axis inelastic neutron spectroscopy, we determine spin-wave excitations throughout the Brillouin zone for ferromagnetic manganites La1?xCaxMnO3 (x=0.25, 0.3) in their lowtemperature 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 La0.7Ca0.3MnO3 are considerably softened in all symmetry directions compared to that of La0.75Ca0.25MnO3. 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.

  19. Small-angle neutron scattering study of magnetic ordering and inhomogeneity across the martensitic phase transformation in Ni50–xCoxMn??Sn?? alloys

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

    Bhatti, Kanwal Preet; El-Khatib, S.; Srivastava, Vijay; James, R. D.; Leighton, C.

    2012-04-01T23:59:59.000Z

    The Heusler-derived multiferroic alloy Ni50–xCoxMn??Sn?? has recently been shown to exhibit, at just above room temperature, a highly reversible martensitic phase transformation with an unusually large magnetization change. In this work the nature of the magnetic ordering above and below this transformation has been studied in detail in the critical composition range x = 6–8 via temperature-dependent (5–600 K) magnetometry and small-angle neutron scattering (SANS). We observe fairly typical paramagnetic to long-range-ordered ferromagnetic phase transitions on cooling to 420–430 K, with the expected critical spin fluctuations, followed by first-order martensitic phase transformations to a nonferromagnetic state below 360–390 K. Themore »static magnetization reveals complex magnetism in this low-temperature nonferromagnetic phase, including a Langevin-like field dependence, distinct spin freezing near 60 K, and significant exchange bias effects, consistent with superparamagnetic blocking of ferromagnetic clusters of nanoscopic dimensions. We demonstrate that these spin clusters, whose existence has been hypothesized in a variety of martensitic alloys exhibiting competition between ferromagnetic and antiferromagnetic exchange interactions, can be directly observed by SANS. The scattering data are consistent with a liquidlike spatial distribution of interacting magnetic clusters with a mean center-to-center spacing of 12 nm. Considering the behavior of the superparmagnetism, cooling-field and temperature-dependent exchange bias, and magnetic SANS, we discuss in detail the physical form and origin of these spin clusters, their intercluster interactions, the nature of the ground-state magnetic ordering in the martensitic phase, and the implications for our understanding of such alloy systems.« less

  20. Small-angle neutron scattering study of magnetic ordering and inhomogeneity across the martensitic phase transformation in Ni50–xCoxMn??Sn?? alloys

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

    Bhatti, Kanwal Preet; El-Khatib, S.; Srivastava, Vijay; James, R. D.; Leighton, C.

    2012-04-01T23:59:59.000Z

    The Heusler-derived multiferroic alloy Ni50–xCoxMn??Sn?? has recently been shown to exhibit, at just above room temperature, a highly reversible martensitic phase transformation with an unusually large magnetization change. In this work the nature of the magnetic ordering above and below this transformation has been studied in detail in the critical composition range x = 6–8 via temperature-dependent (5–600 K) magnetometry and small-angle neutron scattering (SANS). We observe fairly typical paramagnetic to long-range-ordered ferromagnetic phase transitions on cooling to 420–430 K, with the expected critical spin fluctuations, followed by first-order martensitic phase transformations to a nonferromagnetic state below 360–390 K. The static magnetization reveals complex magnetism in this low-temperature nonferromagnetic phase, including a Langevin-like field dependence, distinct spin freezing near 60 K, and significant exchange bias effects, consistent with superparamagnetic blocking of ferromagnetic clusters of nanoscopic dimensions. We demonstrate that these spin clusters, whose existence has been hypothesized in a variety of martensitic alloys exhibiting competition between ferromagnetic and antiferromagnetic exchange interactions, can be directly observed by SANS. The scattering data are consistent with a liquidlike spatial distribution of interacting magnetic clusters with a mean center-to-center spacing of 12 nm. Considering the behavior of the superparmagnetism, cooling-field and temperature-dependent exchange bias, and magnetic SANS, we discuss in detail the physical form and origin of these spin clusters, their intercluster interactions, the nature of the ground-state magnetic ordering in the martensitic phase, and the implications for our understanding of such alloy systems.

  1. Surface driven effects on magnetic properties of antiferromagnetic LaFeO{sub 3} nanocrystalline ferrite

    SciTech Connect (OSTI)

    Sendil Kumar, A., E-mail: sendilphy@gmail.com, E-mail: anilb42@gmail.com [School of Physics, University of Hyderabad, Hyderabad, Telangana 500 046 (India); Manivel Raja, M. [Advanced Magnetics Group, Defence Metallurgical Research Laboratory, Hyderabad, Telangana 500 058 (India); Bhatnagar, Anil K., E-mail: sendilphy@gmail.com, E-mail: anilb42@gmail.com [School of Physics, University of Hyderabad, Hyderabad, Telangana 500 046 (India); School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad, Telangana 500 046 (India)

    2014-09-21T23:59:59.000Z

    LaFeO{sub 3} nanocrystalline ferrites were synthesized through sol-gel method in different size distributions and the effect of finite size on magnetic properties is investigated. Results of magnetization and Mössbauer measurements show that superparamagnetism and weak ferromagnetic behavior in some of the size distributions. The origin of the superparamagnetism is from fine particles similar to ferromagnetic single domains and the weak ferromagnetism comes from surface spin disorder caused by Dzyaloshinskii-Moriya interaction. The magnetic ground state of LaFeO{sub 3} nanoparticles differs from that of bulk, and the ground state is dictated by the finite size effect because density of states depends on the dimensionality of the sample.

  2. Dipolar field effects on the critical current for spin transfer switch of iron and permalloy nanoelements

    SciTech Connect (OSTI)

    Oliveira, L. L.; Dantas, J. T. S.; Souza, R. M.; Carriço, A. S., E-mail: ascarrico@gmail.com [Departamento de Física, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN (Brazil); Dantas, Ana L. [Departamento de Física, Universidade do Estado do Rio Grande do Norte, 59610-210 Mossoró, RN (Brazil)

    2014-05-07T23:59:59.000Z

    We report a theoretical study of dipolar effects on the switching current density of soft ferromagnetic elliptical nanoelements. Relevant changes on the critical current value are found according to the orientation of the magnetization and the spin polarization with the major axis. We show that the critical current density may be reduced by as much as 92% for thin nanoelements magnetized along the minor axis direction, using in-plane spin polarization parallel to the magnetization.

  3. Quantum-state transfer in spin chains via isolated resonance of terminal spins

    E-Print Network [OSTI]

    Kamil Korzekwa; Pawe? Machnikowski; Pawe? Horodecki

    2014-06-03T23:59:59.000Z

    We propose a quantum-state transfer protocol in a spin chain that requires only the control of the spins at the ends of the quantum wire. The protocol is to a large extent insensitive to inhomogeneity caused by local magnetic fields and perturbation of exchange couplings. Moreover, apart from the free evolution regime, it allows one to induce an adiabatic spin transfer, which provides the possibility of performing the transfer on demand. We also show that the amount of information leaking into the central part of the chain is small throughout the whole transfer process (which protects the information sent from being eavesdropped) and can be controlled by the magnitude of the external magnetic field.

  4. The magnetic dipole interaction in Einstein-Maxwell theory

    E-Print Network [OSTI]

    W. B. Bonnor

    2002-03-13T23:59:59.000Z

    I derive an exact, static, axially symmetric solution of the Einstein-Maxwell equations representing two massless magnetic dipoles, and compare it with the corresponding solution of Einstein's equations for two massless spinning particles (see gr-qc/0201094). I then obtain an exact stationary solution of the Einstein-Maxwell equations representing two massless spinning magnets in balance. The conclusion is that the spin-spin force is analogous to the force between two magnetic dipoles, but of opposite sign, and that the latter agrees with the classical value in the first approximation.

  5. The Glass Transition in Fluids with Magnetic Interactions

    E-Print Network [OSTI]

    Ricardo Gutierrez; Bhaskar Sen Gupta; Itamar Procaccia

    2014-06-15T23:59:59.000Z

    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.

  6. A comparative study of magnetic behaviors in TbNi{sub 2}, TbMn{sub 2} and TbNi{sub 2}Mn

    SciTech Connect (OSTI)

    Wang, J. L., E-mail: jianli@uow.edu.au [Institute for Superconductivity and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); Bragg Institute, ANSTO, Lucas Heights, NSW 2234 (Australia); Md Din, M. F.; Hong, F.; Cheng, Z. X.; Dou, S. X. [Institute for Superconductivity and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); Kennedy, S. J.; Studer, A. J. [Bragg Institute, ANSTO, Lucas Heights, NSW 2234 (Australia); Campbell, S. J. [School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, Canberra, ACT 2600 (Australia); Wu, G. H. [Institute of Physics, Chinese Academy of Science, Beijing 100190 (China)

    2014-05-07T23:59:59.000Z

    All TbNi{sub 2}, TbMn{sub 2}, and TbNi{sub 2}Mn compounds exhibit the cubic Laves phase with AB{sub 2}-type structure in spite of the fact that the ratio of the Tb to transition-metal components in TbNi{sub 2}Mn is 1:3. Rietveld refinement indicates that in TbNi{sub 2}Mn the Mn atoms are distributed on both the A (8a) and B (16d) sites. The values of the lattice constants were measured to be a?=?14.348?Å (space group F-43?m), 7.618?Å, and 7.158?Å (space group Fd-3?m) for TbNi{sub 2}, TbMn{sub 2}, and TbNi{sub 2}Mn, respectively. The magnetic transition temperatures T{sub C} were found to be T{sub C}?=?38?K and T{sub C}?=?148?K for TbNi{sub 2} and TbNi{sub 2}Mn, respectively, while two magnetic phase transitions are detected for TbMn{sub 2} at T{sub 1}?=?20?K and T{sub 2}?=?49?K. Clear magnetic history effects in a low magnetic field are observed in TbMn{sub 2} and TbNi{sub 2}Mn. The magnetic entropy changes have been obtained.

  7. NMR with generalized dynamics of spin and spatial coordinates

    SciTech Connect (OSTI)

    Lee, Chang Jae

    1987-11-01T23:59:59.000Z

    This work is concerned with theoretical and experimental aspects of the generalized dynamics of nuclear spin and spatial coordinates under magnetic-field pulses and mechanical motions. The main text begins with an introduction to the concept of ''fictitious'' interactions. A systematic method for constructing fictitious spin-1/2 operators is given. The interaction of spins with a quantized-field is described. The concept of the fictitious interactions under the irradiation of multiple pulses is utilized to design sequences for selectively averaging linear and bilinear operators. Relations between the low-field sequences and high-field iterative schemes are clarified. These relations and the transformation properties of the spin operators are exploited to develop schemes for heteronuclear decoupling of multi-level systems. The resulting schemes are evaluated for heteronuclear decoupling of a dilute spin-1/2 from a spin-1 in liquid crystal samples and from a homonuclear spin-1/2 pair in liquids. A relation between the spin and the spatial variables is discussed. The transformation properties of the spin operators are applied to spatial coordinates and utilized to develop methods for removing the orientational dependence responsible for line broadening in a powder sample. Elimination of the second order quadrupole effects, as well as the first order anisotropies is discussed. It is shown that various sources of line broadening can effectively be eliminated by spinning and/or hopping the sample about judiciously chosen axes along with appropriate radio-frequency pulse sequences.

  8. Development and characterization of the magnetic plasmatron

    E-Print Network [OSTI]

    Anziani, Felipe Rene, 1981-

    2004-01-01T23:59:59.000Z

    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, ...

  9. Magnetic excitations in Kondo liquid: superconductivity and hidden magnetic quantum critical fluctuations

    SciTech Connect (OSTI)

    Yang, Yifeng [Los Alamos National Laboratory; Urbano, Ricardo [NHMFL, FL; Nicholas, Curro [UC DAVIS; Pines, David [UC DAVIS

    2009-01-01T23:59:59.000Z

    We report Knight shift experiments on the superconducting heavy electron material CeCoIn{sub 5} that allow one to track with some precision the behavior of the heavy electron Kondo liquid in the superconducting state with results in agreement with BCS theory. An analysis of the {sup 115}In nuclear quadrupole resonance (NQR) spin-lattice relaxation rate T{sub 1}{sup -1} measurements under pressure reveals the presence of 2d magnetic quantum critical fluctuations in the heavy electron component that are a promising candidate for the pairing mechanism in this material. Our results are consistent with an antiferromagnetic quantum critical point (QCP) located at slightly negative pressure in CeCoIn{sub 5} and provide additional evidence for significant similarities between the heavy electron materials and the high T{sub c} cuprates.

  10. Magnetization dynamics of cobalt grown on graphene

    SciTech Connect (OSTI)

    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

    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.

  11. Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers.

    SciTech Connect (OSTI)

    Mosendz, O.; Vlaminck, V.; Pearson, J. E.; Fradin, F. Y.; Bauer, G. E. W.; Bader, S. D.; Hoffmann, A.; Delft Univ. of Technology

    2010-12-01T23:59:59.000Z

    Spin pumping is a mechanism that generates spin currents from ferromagnetic resonance over macroscopic interfacial areas, thereby enabling sensitive detection of the inverse spin Hall effect that transforms spin into charge currents in nonmagnetic conductors. Here we study the spin-pumping-induced voltages due to the inverse spin Hall effect in permalloy/normal metal bilayers integrated into coplanar waveguides for different normal metals and as a function of angle of the applied magnetic field direction, as well as microwave frequency and power. We find good agreement between experimental data and a theoretical model that includes contributions from anisotropic magnetoresistance and inverse spin Hall effect. The analysis provides consistent results over a wide range of experimental conditions as long as the precise magnetization trajectory is taken into account. The spin Hall angles for Pt, Pd, Au, and Mo were determined with high precision to be 0.013 {+-} 0.002, 0.0064 {+-} 0.001, 0.0035 {+-} 0.0003, and -0.0005 {+-} 0.0001, respectively.

  12. The Quantum Spin Hall Effect: Theory and Experiment

    SciTech Connect (OSTI)

    Konig, Markus; Buhmann, Hartmut; Molenkamp, Laurens W.; /Wurzburg U.; Hughes, Taylor L.; /Stanford U., Phys. Dept.; Liu, Chao-Xing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Qi, Xiao-Liang; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19T23:59:59.000Z

    The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Recently, a new class of topological insulators has been proposed. These topological insulators have an insulating gap in the bulk, but have topologically protected edge states due to the time reversal symmetry. In two dimensions the helical edge states give rise to the quantum spin Hall (QSH) effect, in the absence of any external magnetic field. Here we review a recent theory which predicts that the QSH state can be realized in HgTe/CdTe semiconductor quantum wells. By varying the thickness of the quantum well, the band structure changes from a normal to an 'inverted' type at a critical thickness d{sub c}. We present an analytical solution of the helical edge states and explicitly demonstrate their topological stability. We also review the recent experimental observation of the QSH state in HgTe/(Hg,Cd)Te quantum wells. We review both the fabrication of the sample and the experimental setup. For thin quantum wells with well width d{sub QW} < 6.3 nm, the insulating regime shows the conventional behavior of vanishingly small conductance at low temperature. However, for thicker quantum wells (d{sub QW} > 6.3 nm), the nominally insulating regime shows a plateau of residual conductance close to 2e{sup 2}/h. The residual conductance is independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance is destroyed by a small external magnetic field. The quantum phase transition at the critical thickness, d{sub c} = 6.3 nm, is also independently determined from the occurrence of a magnetic field induced insulator to metal transition.

  13. Spinning particles and higher spin field equations

    E-Print Network [OSTI]

    Bastianelli, Fiorenzo; Corradini, Olindo; Latini, Emanuele

    2015-01-01T23:59:59.000Z

    Relativistic particles with higher spin can be described in first quantization using actions with local supersymmetry on the worldline. First, we present a brief review of these actions and their use in first quantization. In a Dirac quantization scheme the field equations emerge as Dirac constraints on the Hilbert space, and we outline how they lead to the description of higher spin fields in terms of the more standard Fronsdal-Labastida equations. Then, we describe how these actions can be extended so that the propagating particle is allowed to take different values of the spin, i.e. carry a reducible representation of the Poincar\\'e group. This way one may identify a four dimensional model that carries the same degrees of freedom of the minimal Vasiliev's interacting higher spin field theory. Extensions to massive particles and to propagation on (A)dS spaces are also briefly commented upon.

  14. Zero field high frequency oscillations in dual free layer spin torque oscillators

    SciTech Connect (OSTI)

    Braganca, P. M., E-mail: patrick.braganca@hgst.com; Pi, K.; Zakai, R.; Childress, J. R.; Gurney, B. A. [HGST, 3404 Yerba Buena Rd., San Jose, California 95135 (United States)] [HGST, 3404 Yerba Buena Rd., San Jose, California 95135 (United States)

    2013-12-02T23:59:59.000Z

    We observe microwave oscillations in relatively simple spin valve spin torque oscillators consisting of two in-plane free layers without spin polarizing layers. These devices exhibit two distinct modes which can reach frequencies >25?GHz in the absence of an applied magnetic field. Macrospin simulations identify these two modes as optical and acoustic modes excited by the coupling of the two layers through dipole field and spin torque effects. These results demonstrate the potential of this system as a large output power, ultrahigh frequency signal generator that can operate without magnetic field.

  15. Anisotropic rare-earth spin ensemble strongly coupled to a superconducting resonator

    E-Print Network [OSTI]

    S. Probst; H. Rotzinger; S. Wünsch; P. Jung; M. Jerger; M. Siegel; A. V. Ustinov; P. A. Bushev

    2012-12-12T23:59:59.000Z

    Interfacing photonic and solid-state qubits within a hybrid quantum architecture offers a promising route towards large scale distributed quantum computing. Ideal candidates for coherent qubit interconversion are optically active spins magnetically coupled to a superconducting resonator. We report on a cavity QED experiment with magnetically anisotropic Er3+:Y2SiO5 crystals and demonstrate strong coupling of rare-earth spins to a lumped element resonator. In addition, the electron spin resonance and relaxation dynamics of the erbium spins are detected via direct microwave absorption, without aid of a cavity.

  16. Optimized fabrication and characterization of carbon nanotube spin valves

    SciTech Connect (OSTI)

    Samm, J.; Gramich, J.; Baumgartner, A., E-mail: andreas.baumgartner@unibas.ch; Weiss, M.; Schönenberger, C. [Institute of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland)

    2014-05-07T23:59:59.000Z

    We report an improved fabrication scheme for carbon based nanospintronic devices and demonstrate the necessity for a careful data analysis to investigate the fundamental physical mechanisms leading to magnetoresistance. The processing with a low-density polymer and an optimised recipe allows us to improve the electrical, magnetic, and structural quality of ferromagnetic Permalloy contacts on lateral carbon nanotube (CNT) quantum dot spin valve devices, with comparable results for thermal and sputter deposition of the material. We show that spintronic nanostructures require an extended data analysis, since the magnetization can affect all characteristic parameters of the conductance features and lead to seemingly anomalous spin transport. In addition, we report measurements on CNT quantum dot spin valves that seem not to be compatible with the orthodox theories for spin transport in such structures.

  17. Interaction induced staggered spin-orbit order in two-dimensional electron gas

    SciTech Connect (OSTI)

    Das, Tanmoy [Los Alamos National Laboratory

    2012-06-05T23:59:59.000Z

    Decoupling spin and charge transports in solids is among the many prerequisites for realizing spin electronics, spin caloritronics, and spin-Hall effect. Beyond the conventional method of generating and manipulating spin current via magnetic knob, recent advances have expanded the possibility to optical and electrical method which are controllable both internally and externally. Yet, due to the inevitable presence of charge excitations and electrical polarizibility in these methods, the separation between spin and charge degrees of freedom of electrons remains a challenge. Here we propose and formulate an interaction induced staggered spin-orbit order as a new emergent phase of matter. We show that when some form of inherent spin-splitting via Rashba-type spin-orbit coupling renders two helical Fermi surfaces to become significantly nested, a Fermi surface instability arises. To lift this degeneracy, a spontaneous symmetry breaking spin-orbit density wave develops, causing a surprisingly large quasiparticle gapping with chiral electronic states, with no active charge excitations. Since the staggered spin-orbit order is associated with a condensation energy, quantified by the gap value, destroying such spin-orbit interaction costs sufficiently large perturbation field or temperature or de-phasing time. BiAg2 surface state is shown to be a representative system for realizing such novel spin-orbit interaction with tunable and large strength, and the spin-splitting is decoupled from charge excitations.

  18. Self-oscillation in spin torque oscillator stabilized by field-like torque

    SciTech Connect (OSTI)

    Taniguchi, Tomohiro; Tsunegi, Sumito; Kubota, Hitoshi; Imamura, Hiroshi [National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba 305-8568 (Japan)

    2014-04-14T23:59:59.000Z

    The effect of the field-like torque on the self-oscillation of the magnetization in spin torque oscillator with a perpendicularly magnetized free layer was studied theoretically. A stable self-oscillation at zero field is excited for negative ? while the magnetization dynamics stops for ??=?0 or ??>?0, where ? is the ratio between the spin torque and the field-like torque. The reason why only the negative ? induces the self-oscillation was explained from the view point of the energy balance between the spin torque and the damping. The oscillation power and frequency for various ? were also studied by numerical simulation.

  19. Imaging of lateral spin valves with soft x-ray microscopy

    SciTech Connect (OSTI)

    Mosendz, O.; Mihajlovic, G.; Pearson, J. E.; Fischer, P.; Im, M.-Y.; Bader, S. D.; Hoffmann, A.

    2009-05-01T23:59:59.000Z

    We investigated Co/Cu lateral spin valves by means of high-resolution transmission soft x-ray microscopy with magnetic contrast that utilizes x-ray magnetic circular dichroism (XMCD). No magnetic XMCD contrast was observed at the Cu L{sub 3} absorption edge, which should directly image the spin accumulation in Cu. Although electrical transport measurements in a non-local geometry clearly detected the spin accumulation in Cu, which remained unchanged during illumination with circular polarized x-rays at the Co and Cu L{sub 3} absorption edges.

  20. Imaging of lateral spin valves with soft x-ray microscopy.

    SciTech Connect (OSTI)

    Mosendz, O.; Mihajlovic, G.; Pearson, J. E.; Fischer, P.; Im, M.-Y.; Bader, S. D.; Hoffmann, A.; LBNL

    2009-01-01T23:59:59.000Z

    We investigated Co/Cu lateral spin valves by means of high-resolution transmission soft x-ray microscopy with magnetic contrast that utilizes x-ray magnetic circular dichroism (XMCD). No magnetic XMCD contrast was observed at the Cu L{sub 3} absorption edge, which should directly image the spin accumulation in Cu, although electrical transport measurements in a nonlocal geometry clearly detected the spin accumulation in Cu, which remained unchanged during illumination with circular polarized x rays at the Co and Cu L{sub 3} absorption edges.

  1. Nuclear Spins in a Nanoscale Device for Quantum Information Processing

    E-Print Network [OSTI]

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

    2006-12-29T23:59:59.000Z

    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, $M_z$.

  2. Orbital and spin scissors modes in superfluid nuclei

    E-Print Network [OSTI]

    Balbutsev, E B; Schuck, P

    2015-01-01T23:59:59.000Z

    Nuclear scissors modes are considered in the frame of Wigner function moments method generalized to take into account spin degrees of freedom and pair correlations simultaneously. A new source of nuclear magnetism, connected with counter-rotation of spins up and down around the symmetry axis (hidden angular momenta), is discovered. Its inclusion into the theory allows one to improve substantially the agreement with experimental data in the description of energies and transition probabilities of scissors modes in rare earth nuclei.

  3. Orbital and spin scissors modes in superfluid nuclei

    E-Print Network [OSTI]

    E. B. Balbutsev; I. V. Molodtsova; P. Schuck

    2015-02-19T23:59:59.000Z

    Nuclear scissors modes are considered in the frame of Wigner function moments method generalized to take into account spin degrees of freedom and pair correlations simultaneously. A new source of nuclear magnetism, connected with counter-rotation of spins up and down around the symmetry axis (hidden angular momenta), is discovered. Its inclusion into the theory allows one to improve substantially the agreement with experimental data in the description of energies and transition probabilities of scissors modes in rare earth nuclei.

  4. Quantum Information Processing by NMR using strongly coupled spins

    E-Print Network [OSTI]

    T. S. Mahesh; Neeraj Sinha; Arindam Ghosh; Ranabir Das; N. Suryaprakash; Malcom H. Levitt; K. V. Ramanathan; Anil Kumar

    2003-11-24T23:59:59.000Z

    The enormous theoretical potential of Quantum Information Processing (QIP) is driving the pursuit for its practical realization by various physical techniques. Currently Nuclear Magnetic Resonance (NMR) has been the forerunner by demonstrating a majority of quantum algorithms. In NMR, spin systems consisting of coupled nuclear spins are utilized as qubits. In order to carry out QIP, a spin system has to meet two major requirements: (i) qubit addressability and (ii) mutual coupling among the qubits. It has been demonstrated that the magnitude of the mutual coupling among qubits can be increased by orienting the spin-systems in a liquid crystal matrix and utilizing the residual dipolar couplings. While utilizing residual dipolar couplings may be useful to increase the number of qubits, nuclei of same species (homonuclei) might become strongly coupled. In strongly coupled spin-systems, spins loose their individual identity of being qubits. We propose that even such strongly coupled spin-systems can be used for QIP and the qubit-manipulation can be achieved by transition-selective pulses. We demonstrate experimental preparation of pseudopure states, creation of maximally entangled states, implementation logic gates and implementation of Deutsch-Jozsa (DJ) algorithm in strongly coupled 2,3 and 4 spin systems. The energy levels of the strongly coupled 3 and 4 spin systems were obtained by using a Z-COSY experiment.

  5. Non-Abelian hydrodynamics and the flow of spin in spin-orbit coupled substances

    SciTech Connect (OSTI)

    Leurs, B.W.A. [Instituut Lorentz for Theoretical Physics, Leiden University, Leiden (Netherlands)], E-mail: leurs@lorentz.leidenuniv.nl; Nazario, Z.; Santiago, D.I.; Zaanen, J. [Instituut Lorentz for Theoretical Physics, Leiden University, Leiden (Netherlands)

    2008-04-15T23:59:59.000Z

    Motivated by the heavy ion collision experiments there is much activity in studying the hydrodynamical properties of non-Abelian (quark-gluon) plasmas. A major question is how to deal with color currents. Although not widely appreciated, quite similar issues arise in condensed matter physics in the context of the transport of spins in the presence of spin-orbit coupling. The key insight is that the Pauli Hamiltonian governing the leading relativistic corrections in condensed matter systems can be rewritten in a language of SU(2) covariant derivatives where the role of the non-Abelian gauge fields is taken by the physical electromagnetic fields: the Pauli system can be viewed as Yang-Mills quantum-mechanics in a 'fixed frame', and it can be viewed as an 'analogous system' for non-Abelian transport in the same spirit as Volovik's identification of the He superfluids as analogies for quantum fields in curved space time. We take a similar perspective as Jackiw and coworkers in their recent study of non-Abelian hydrodynamics, twisting the interpretation into the 'fixed frame' context, to find out what this means for spin transport in condensed matter systems. We present an extension of Jackiw's scheme: non-Abelian hydrodynamical currents can be factored in a 'non-coherent' classical part, and a coherent part requiring macroscopic non-Abelian quantum entanglement. Hereby it becomes particularly manifest that non-Abelian fluid flow is a much richer affair than familiar hydrodynamics, and this permits us to classify the various spin transport phenomena in condensed matter physics in an unifying framework. The 'particle based hydrodynamics' of Jackiw et al. is recognized as the high temperature spin transport associated with semiconductor spintronics. In this context the absence of faithful hydrodynamics is well known, but in our formulation it is directly associated with the fact that the covariant conservation of non-Abelian currents turns into a disastrous non-conservation of the incoherent spin currents of the high temperature limit. We analyze the quantum-mechanical single particle currents of relevance to mesoscopic transport with as highlight the Ahronov-Casher effect, where we demonstrate that the intricacies of the non-Abelian transport render this effect to be much more fragile than its abelian analog, the Ahronov-Bohm effect. We subsequently focus on spin flows protected by order parameters. At present there is much interest in multiferroics where non-collinear magnetic order triggers macroscopic electric polarization via the spin-orbit coupling. We identify this to be a peculiarity of coherent non-Abelian hydrodynamics: although there is no net particle transport, the spin entanglement is transported in these magnets and the coherent spin 'super' current in turn translates into electric fields with the bonus that due to the requirement of single valuedness of the magnetic order parameter a true hydrodynamics is restored. Finally, 'fixed-frame' coherent non-Abelian transport comes to its full glory in spin-orbit coupled 'spin superfluids', and we demonstrate a new effect: the trapping of electrical line charge being a fixed frame, non-Abelian analog of the familiar magnetic flux trapping by normal superconductors. The only known physical examples of such spin superfluids are the {sup 3}He A- and B-phase where unfortunately the spin-orbit coupling is so weak that it appears impossible to observe these effects.

  6. Time-dependent model for diluted magnetic semiconductors including band structure and confinement effects

    E-Print Network [OSTI]

    Boyer, Edmond

    Time-dependent model for diluted magnetic semiconductors including band structure and confinement dynamics in confined diluted magnetic semiconductors induced by laser. The hole-spin relaxation process light-induced magnetization dynamics in ferro- magnetic films and in diluted magnetic semiconductors DMS

  7. Outline for the next couple of lectures -Magnetism and the Ising Model (today's lecture)

    E-Print Network [OSTI]

    Ceder, Gerbrand

    Outline for the next couple of lectures -Magnetism and the Ising Model (today's lecture) -Liquid-field solution to magnetism are equivalent. -Thermodynamic results in magnetism, such as the critical (or Curie) temperature below which spontaneous magnetization occurs. #12;Magnetism: The Ising Model 1) Spins can be only

  8. Spin coating apparatus

    DOE Patents [OSTI]

    Torczynski, John R. (Albuquerque, NM)

    2000-01-01T23:59:59.000Z

    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.

  9. Entangled spin clusters: Some special features

    SciTech Connect (OSTI)

    Tribedi, Amit; Bose, Indrani [Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata-700 009 (India)

    2006-07-15T23:59:59.000Z

    In this paper, we study three specific aspects of entanglement in small spin clusters. We first study the effect of inhomogeneous exchange coupling strengths on the entanglement properties of the S=(1/2) antiferromagnetic linear chain tetramer compound NaCuAsO{sub 4}. The entanglement gap temperature T{sub E} is found to have a nonmonotonic dependence on the value of {alpha}, the exchange coupling inhomogeneity parameter. We next determine the variation of T{sub E} as a function of S for a spin dimer, a trimer, and a tetrahedron. The temperature T{sub E} is found to increase as a function of S but the scaled entanglement gap temperature t{sub E} goes to zero as S becomes large. Last, we study a spin-1 dimer compound to illustrate the quantum complementarity relation. We show that in the experimentally realizable parameter region, magnetization and entanglement plateaus appear simultaneously at low temperatures as a function of the magnetic field. Also, the sharp increase in one quantity as a function of the magnetic field is accompanied by a sharp decrease in the other so that the quantum complementarity relation is not violated.

  10. All-electric and all-semiconductor spin field effect transistors

    E-Print Network [OSTI]

    Chuang, Pojen; Ho, Sheng-Chin; Smith, L. W.; Sfigakis, F.; Pepper, M.; Chen, Chin-Hung; Fan, Ju-Chun; Griffiths, J. P.; Farrer, I.; Beere, H. E.; Jones, G. A. C.; Ritchie, D. A.; Chen, T.-M.

    2015-01-01T23:59:59.000Z

    which suffers from low signal levels as a result of the limited spin-injection efficiency, the short spin lifetime, and the spread of spin precession angles. The voltage oscillation disappears when the lateral inversion asymmetry is removed from the QPCs... to showing the realization of spin FETs, provide the first direct evidence of spin polarization of QPCs at zero external magnetic field. Figure 3a shows the oscillating voltages when the injector and detector QPCs are set at various conductance values. In a...

  11. Local spin torque induced by electron electric dipole moment in the YbF molecule

    SciTech Connect (OSTI)

    Fukuda, Masahiro; Senami, Masato; Ogiso, Yoji; Tachibana, Akitomo [Department of Micro Engineering, Kyoto University, Kyoto 615-8540 (Japan)

    2014-10-06T23:59:59.000Z

    In this study, we show the modification of the equation of motion of the electronic spin, which is derived by the quantum electron spin vorticity principle, by the effect of the electron electric dipole moment (EDM). To investigate the new contribution to spin torque by EDM, using first principle calculations, we visualize distributions of the local spin angular momentum density and local spin torque density of the YbF molecule on which the static electric field and magnetic field are applied at t = 0.

  12. 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]

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

    2014-11-07T23:59:59.000Z

    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.

  13. Spin-based quantum computing using electrons on liquid helium

    E-Print Network [OSTI]

    S. A. Lyon

    2006-11-17T23:59:59.000Z

    Numerous physical systems have been proposed for constructing quantum computers, but formidable obstacles stand in the way of making even modest systems with a few hundred quantum bits (qubits). Several approaches utilize the spin of an electron as the qubit. Here it is suggested that the spin of electrons floating on the surface of liquid helium will make excellent qubits. These electrons can be electrostatically held and manipulated much like electrons in semiconductor heterostructures, but being in a vacuum the spins on helium suffer much less decoherence. In particular, the spin orbit interaction is reduced so that moving the qubits with voltages applied to gates has little effect on their coherence. Remaining sources of decoherence are considered and it is found that coherence times for electron spins on helium can be expected to exceed 100 s. It is shown how to obtain a controlled-NOT operation between two qubits using the magnetic dipole-dipole interaction.

  14. Size dependence of magnetization switching and its dispersion of Co/Pt nanodots under the assistance of radio frequency fields

    SciTech Connect (OSTI)

    Furuta, Masaki, E-mail: furutam@mail.tagen.tohoku.ac.jp; Okamoto, Satoshi; Kikuchi, Nobuaki; Kitakami, Osamu [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Shimatsu, Takehito [Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578 (Japan); Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan)

    2014-04-07T23:59:59.000Z

    We have studied the dot size dependence of microwave assisted magnetization switching (MAS) on perpendicular magnetic Co/Pt multilayer dot array. The significant microwave assistance effect has been observed over the entire dot size D ranging from 50?nm to 330?nm examined in the present study. The MAS behavior, however, critically depends on D. The excitation frequency dependence of the switching field is well consistent with the spin wave theory, indicating that the magnetization precession in MAS is in accordance with the well defined eigenmodes depending on the dot diameter. The lowest order spin wave is only excited for D???100?nm, and then the MAS effect is well consistent with that of the single macrospin prediction. On the other hand, higher order spin waves are excited for D?>?100?nm, giving rise to the significant enhancement of the MAS effect. The dispersion of MAS effect also depends on D and is significantly reduced for the region of D?>?100?nm. This significant reduction of the dispersion is attributed to the essential feature of the MAS effect which is insensitive to the local fluctuation of anisotropy field, such as defect, damaged layer, and so on.

  15. Dipolar Spin Models with Arrays of Superconducting Qubits

    E-Print Network [OSTI]

    M. Dalmonte; S. I. Mirzai; P. R. Muppalla; D. Marcos; P. Zoller; G. Kirchmair

    2015-01-13T23:59:59.000Z

    We propose a novel platform for quantum many body simulations of dipolar spin models using current circuit QED technology. Our basic building blocks are 3D Transmon qubits where we use the naturally occurring dipolar interactions to realize interacting spin systems. This opens the way toward the realization of a broad class of tunable spin models in both two- and one-dimensional geometries. We illustrate the potential offered by these systems in the context of dimerized Majumdar-Ghosh-type phases, archetypical examples of quantum magnetism, showing how such phases are robust against disorder and decoherence, and could be observed within state-of-the-art experiments.

  16. Nuclear spin qubits in a trapped-ion quantum computer

    E-Print Network [OSTI]

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

    2009-04-26T23:59:59.000Z

    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.

  17. Nanoconstriction-based spin-Hall nano-oscillator

    SciTech Connect (OSTI)

    Demidov, V. E., E-mail: demidov@uni-muenster.de [Department of Physics and Center for Nonlinear Science, University of Muenster, Corrensstr. 2-4, 48149 Muenster (Germany); Urazhdin, S.; Zholud, A. [Department of Physics, Emory University, 400 Dowman Dr., Atlanta, Georgia 30322 (United States); Sadovnikov, A. V. [Department of Physics and Center for Nonlinear Science, University of Muenster, Corrensstr. 2-4, 48149 Muenster (Germany); Saratov State University, 83 Astrakhanskaya str., Saratov 410012 (Russian Federation); Demokritov, S. O. [Department of Physics and Center for Nonlinear Science, University of Muenster, Corrensstr. 2-4, 48149 Muenster (Germany); Institute of Metal Physics, Ural Division of RAS, Yekaterinburg 620041 (Russian Federation)

    2014-10-27T23:59:59.000Z

    We experimentally demonstrate magnetic nano-oscillators driven by pure spin current produced by the spin Hall effect in a bow tie-shaped nanoconstriction. These devices exhibit single-mode auto-oscillation and generate highly-coherent electronic microwave signals with a significant power and the spectral linewidth as low as 6.2?MHz at room temperature. The proposed simple and flexible device geometry is amenable to straightforward implementation of advanced spintronic structures such as chains of mutually coupled spin-Hall nano-oscillators.

  18. Small-angle neutron scattering study of magnetic ordering and inhomogeneity across the martensitic phase transformation in Ni50–xCoxMn??Sn?? alloys

    SciTech Connect (OSTI)

    Bhatti, Kanwal Preet; El-Khatib, S.; Srivastava, Vijay; James, R. D.; Leighton, C.

    2012-04-01T23:59:59.000Z

    The Heusler-derived multiferroic alloy Ni50–xCoxMn??Sn?? has recently been shown to exhibit, at just above room temperature, a highly reversible martensitic phase transformation with an unusually large magnetization change. In this work the nature of the magnetic ordering above and below this transformation has been studied in detail in the critical composition range x = 6–8 via temperature-dependent (5–600 K) magnetometry and small-angle neutron scattering (SANS). We observe fairly typical paramagnetic to long-range-ordered ferromagnetic phase transitions on cooling to 420–430 K, with the expected critical spin fluctuations, followed by first-order martensitic phase transformations to a nonferromagnetic state below 360–390 K. The static magnetization reveals complex magnetism in this low-temperature nonferromagnetic phase, including a Langevin-like field dependence, distinct spin freezing near 60 K, and significant exchange bias effects, consistent with superparamagnetic blocking of ferromagnetic clusters of nanoscopic dimensions. We demonstrate that these spin clusters, whose existence has been hypothesized in a variety of martensitic alloys exhibiting competition between ferromagnetic and antiferromagnetic exchange interactions, can be directly observed by SANS. The scattering data are consistent with a liquidlike spatial distribution of interacting magnetic clusters with a mean center-to-center spacing of 12 nm. Considering the behavior of the superparmagnetism, cooling-field and temperature-dependent exchange bias, and magnetic SANS, we discuss in detail the physical form and origin of these spin clusters, their intercluster interactions, the nature of the ground-state magnetic ordering in the martensitic phase, and the implications for our understanding of such alloy systems.

  19. Effects of spin doping and spin injection in the luminescence and vibrational spectrum of C{sub 60}

    SciTech Connect (OSTI)

    Moorsom, Timothy; Wheeler, May; Taukeer Khan, Mohd; Al Ma'Mari, Fatma; Burnell, Gavin; Hickey, Bryan J.; Cespedes, Oscar, E-mail: o.cespedes@leeds.ac.uk [School of Physics and Astronomy, University of Leeds, LS2 9JT W. Yorkshire (United Kingdom); Lazarov, Vlado; Gilks, Daniel [Department of Physics, University of York, YO10 5DD N. Yorkshire (United Kingdom)

    2014-07-14T23:59:59.000Z

    We have studied the Raman spectrum and photoemission of hybrid magneto-fullerene devices. For C{sub 60} layers on cobalt, the spin polarized electron transfer shifts the photoemission energy, reducing the zero phonon contribution. The total luminescence of hybrid devices can be controlled via spin injection from magnetic electrodes, with changes of the order of 10%–20% at room temperature. Spin polarised currents alter as well the Raman spectrum of the molecules, enhancing some modes by a factor 5 while shifting others by several wavenumbers due to a spin-dependent hopping time and/or enhanced intermolecular interactions. These results can be used to measure spin polarisation in molecules or to fabricate magneto-optic and magneto-vibrational devices.

  20. np elastic spin transfer measurements at 788 MeV

    E-Print Network [OSTI]

    McNaughton, M. W.; Koch, K.; Supek, I.; Tanaka, N.; McNaughton, K. H.; Riley, P. J.; Ambrose, DA; Johnson, J. D.; Smith, A.; Glass, G.; Hiebert, John C.; Northcliffe, L. C.; Simon, A. J.; Adams, D. L.; Ransome, R. D.; Clayton, D. B.; Spinka, H. M.; Jepperson, R. H.; Tripard, G. E.

    1991-01-01T23:59:59.000Z

    PHYSICAL REVIEW C VOLUME 44, NUMBER 6 DECEMBER 1991 ARTICLES np elastic spin transfer measurements at 788 MeV M. W. McNaughton, K. Koch, I. Supek, and N. Tanaka Los Alamos National Laboratory, Los Alamos, New Mexico 87545 K. H. McNaughton, P. J... radius of about 3 rnm and centered on the 25-cm-thick liquid-deuterium (LD2) neutron-production target. B. Neutron beam magnets (LBBM6,7). The neutrons passed through the fringe fields of these magnets and were precessed about 50' from L spin. A...

  1. Effect of spin rotation coupling on spin transport

    SciTech Connect (OSTI)

    Chowdhury, Debashree, E-mail: debashreephys@gmail.com; Basu, B., E-mail: sribbasu@gmail.com

    2013-12-15T23:59:59.000Z

    We have studied the spin rotation coupling (SRC) as an ingredient to explain different spin-related issues. This special kind of coupling can play the role of a Dresselhaus like coupling in certain conditions. Consequently, one can control the spin splitting, induced by the Dresselhaus like term, which is unusual in a semiconductor heterostructure. Within this framework, we also study the renormalization of the spin-dependent electric field and spin current due to the k{sup ?}?p{sup ?} perturbation, by taking into account the interband mixing in the rotating system. In this paper we predict the enhancement of the spin-dependent electric field resulting from the renormalized spin rotation coupling. The renormalization factor of the spin electric field is different from that of the SRC or Zeeman coupling. The effect of renormalized SRC on spin current and Berry curvature is also studied. Interestingly, in the presence of this SRC-induced SOC it is possible to describe spin splitting as well as spin galvanic effect in semiconductors. -- Highlights: •Studied effect of spin rotation coupling on the spin electric field, spin current and Berry curvature. •In the k{sup ?}?p{sup ?} framework we study the renormalization of spin electric field and spin current. •For an inertial system we have discussed the spin splitting. •Expression for the Berry phase in the inertial system is discussed. •The inertial spin galvanic effect is studied.

  2. The electric field manipulation of magnetization in La{sub 1?x}Sr{sub x}CoO{sub 3}/Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-PbTiO{sub 3} heterostructures

    SciTech Connect (OSTI)

    Zhang, Q. M.; Li, Q.; Zhou, W. P.; Wang, L. Y.; Yang, Y. T.; Wang, D. H., E-mail: wangdh@nju.edu.cn; Lv, L. Y.; Du, Y. W. [Jiangsu Key Laboratory for Nano Technology and National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Gao, R. L. [School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331 (China)

    2014-04-07T23:59:59.000Z

    La{sub 1?x}Sr{sub x}CoO{sub 3} (x?=?0.18, 0.33, and 0.5) films were grown epitaxially on piezoelectric Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-PbTiO{sub 3} substrates by pulsed laser deposition. The magnetization of these films varies with the external electric field, showing the magnetoelectric effect. With different doping content of Sr{sup 2+} ions, the change of magnetization for these films show different behaviors with increasing temperature, which can be attributed to the competition between electric-field-induced changes of spin state and double exchange interaction. This work presents an alternative mechanism to investigate the electric field control of magnetism in magnetoelectric heterostructure by tuning the spin state.

  3. Layering and temperature-dependent magnetization and anisotropy of naturally produced Ni/NiO multilayers

    SciTech Connect (OSTI)

    Pappas, S. D.; Trachylis, D.; Velgakis, M. J. [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Kapaklis, V.; Joensson, P. E.; Papaioannou, E. Th. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden); Delimitis, A. [Chemical Process Engineering Research Institute (CPERI), Centre for Research and Technology Hellas (CERTH), 57001 Thermi, Thessaloniki (Greece); Poulopoulos, P. [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Institut fuer Experimentalphysik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin-Dahlem (Germany); Materials Science Department, University of Patras, 26504 Patras (Greece); Fumagalli, P. [Institut fuer Experimentalphysik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin-Dahlem (Germany); Politis, C. [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019 (United States)

    2012-09-01T23:59:59.000Z

    Ni/NiO multilayers were grown by magnetron sputtering at room temperature, with the aid of the natural oxidation procedure. That is, at the end of the deposition of each single Ni layer, air is let to flow into the vacuum chamber through a leak valve. Then, a very thin NiO layer ({approx}1.2 nm) is formed. Simulated x-ray reflectivity patterns reveal that layering is excellent for individual Ni-layer thickness larger than 2.5 nm, which is attributed to the intercalation of amorphous NiO between the polycrystalline Ni layers. The magnetization of the films, measured at temperatures 5-300 K, has almost bulk-like value, whereas the films exhibit a trend to perpendicular magnetic anisotropy (PMA) with an unusual significant positive interface anisotropy contribution, which presents a weak temperature dependence. The power-law behavior of the multilayers indicates a non-negligible contribution of higher order anisotropies in the uniaxial anisotropy. Bloch-law fittings for the temperature dependence of the magnetization in the spin-wave regime show that the magnetization in the multilayers decreases faster as a function of temperature than the one of bulk Ni. Finally, when the individual Ni-layer thickness decreases below 2 nm, the multilayer stacking vanishes, resulting in a dramatic decrease of the interface magnetic anisotropy and consequently in a decrease of the perpendicular magnetic anisotropy.

  4. Electric Dipole Moment of Magnetic Monopole

    E-Print Network [OSTI]

    Makoto Kobayashi

    2007-03-07T23:59:59.000Z

    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).

  5. Spin coating of electrolytes

    DOE Patents [OSTI]

    Stetter, Joseph R. (Naperville, IL); Maclay, G. Jordan (Maywood, IL)

    1989-01-01T23:59:59.000Z

    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.

  6. Inertial effect on spin–orbit coupling and spin transport

    SciTech Connect (OSTI)

    Basu, B., E-mail: sribbasu@gmail.com; Chowdhury, Debashree, E-mail: debashreephys@gmail.com

    2013-08-15T23:59:59.000Z

    We theoretically study the renormalization of inertial effects on the spin dependent transport of conduction electrons in a semiconductor by taking into account the interband mixing on the basis of k{sup ?}?p{sup ?} perturbation theory. In our analysis, for the generation of spin current we have used the extended Drude model where the spin–orbit coupling plays an important role. We predict enhancement of the spin current resulting from the renormalized spin–orbit coupling effective in our model in cubic and non-cubic crystals. Attention has been paid to clarify the importance of gauge fields in the spin transport of this inertial system. A theoretical proposition of a perfect spin filter has been done through the Aharonov–Casher like phase corresponding to this inertial system. For a time dependent acceleration, effect of k{sup ?}?p{sup ?} perturbation on the spin current and spin polarization has also been addressed. Furthermore, achievement of a tunable source of polarized spin current through the non uniformity of the inertial spin–orbit coupling strength has also been discussed. -- Highlights: •Study of the renormalization of inertial spin dependent transport of electrons. •Enhancement of the spin current due to the renormalized spin–orbit coupling. •A theoretical proposition of a perfect spin filter. •For a time dependent acceleration, spin current, spin polarization is addressed.

  7. Optimization of a microwave resonator cavity to perform electron spin resonance measurements on quantum dots

    E-Print Network [OSTI]

    Burger, Anat

    2006-01-01T23:59:59.000Z

    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 ...

  8. Physics 139B Midterm Exam Solutions Fall 2009 1. Consider a spin 1

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    Physics 139B Midterm Exam Solutions Fall 2009 1. Consider a spin­ 1 2 particle with magnetic moment be rewritten as c + = cos( 1 4 # o T ) , c - = -i si

  9. Muon spin rotation studies of niobium for superconducting RF applications

    E-Print Network [OSTI]

    Grassellino, A; Kolb, P; Laxdal, R; Lockyer, N S; Longuevergne, D; Sonier, J E

    2013-01-01T23:59:59.000Z

    In this work we investigate superconducting properties of niobium samples via application of the muon spin rotation/relaxation (muSR) technique. We employ for the first time the muSR technique to study samples that are cutout from large and small grain 1.5 GHz radio frequency (RF) single cell niobium cavities. The RF test of these cavities was accompanied by full temperature mapping to characterize the RF losses in each of the samples. Results of the muSR measurements show that standard cavity surface treatments like mild baking and buffered chemical polishing (BCP) performed on the studied samples affect their surface pinning strength. We find an interesting correlation between high field RF losses and field dependence of the sample magnetic volume fraction measured via muSR. The muSR line width observed in ZF-muSR measurements matches the behavior of Nb samples doped with minute amounts of Ta or N impurities. An upper bound for the upper critical field Hc2 of these cutouts is found.

  10. Optical detection of spin Hall effect in metals

    SciTech Connect (OSTI)

    Erve, O. M. J. van ‘t, E-mail: Olaf.Vanterve@nrl.navy.mil; Hanbicki, A. T.; McCreary, K. M.; Li, C. H.; Jonker, B. T. [Materials Science and Technology Division, Naval Research Laboratory, Washington, DC 20375 (United States)

    2014-04-28T23:59:59.000Z

    Optical techniques have been widely used to probe the spin Hall effect in semiconductors. In metals, however, only electrical methods such as nonlocal spin valve transport, ferromagnetic resonance, or spin torque transfer experiments have been successful. These methods require complex processing techniques and measuring setups. We show here that the spin Hall effect can be observed in non-magnetic metals such as Pt and ?-W, using a standard bench top magneto-optical Kerr system with very little sample preparation. Applying a square wave current and using Fourier analysis significantly improve our detection level. One can readily determine the angular dependence of the induced polarization on the bias current direction (very difficult to do with voltage detection), the orientation of the spin Hall induced polarization, and the sign of the spin Hall angle. This optical approach is free from the complications of various resistive effects, which can compromise voltage measurements. This opens up the study of spin Hall effect in metals to a variety of spin dynamic and spatial imaging experiments.

  11. Strong mechanical driving of a single electron spin

    E-Print Network [OSTI]

    Arne Barfuss; Jean Teissier; Elke Neu; Andreas Nunnenkamp; Patrick Maletinsky

    2015-03-23T23:59:59.000Z

    Quantum devices for sensing and computing applications require coherent quantum systems which can be manipulated in a fast and robust way. Such quantum control is typically achieved using external electric or magnetic fields which drive the system's orbital or spin degrees of freedom. However, most of these approaches require complex and unwieldy antenna or gate structures, and with few exceptions are limited to the regime of weak driving. Here, we present a novel approach to strongly and coherently drive a single electron spin in the solid state using internal strain fields in an integrated quantum device. Specifically, we study individual Nitrogen-Vacancy (NV) spins embedded in diamond mechanical oscillators and exploit the intrinsic strain coupling between spin and oscillator to strongly drive the spins. As hallmarks of the strong driving regime, we directly observe the energy spectrum of the emerging phonon-dressed states and employ our strong, continuous driving for enhancement of the NV spin coherence time. Our results constitute a first step towards strain-driven, integrated quantum devices and open new perspectives to investigate unexplored regimes of strongly driven multi-level systems and to study exotic spin dynamics in hybrid spin-oscillator devices.

  12. EUROPEAN CONFERENCE FOR AEROSPACE SCIENCES Study on the eddy current damping of the spin dynamics of

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    4TH EUROPEAN CONFERENCE FOR AEROSPACE SCIENCES Study on the eddy current damping of the spin consideration in this article, are impacted by torques generated by eddy currents as the conducting non, the permanent magnetic field from the magnetosphere generates eddy current in the spinning, conducting body

  13. Nanostructural considerations in giant magnetoresistive Co-Cu-based symmetric spin valves Harsh Deep Chopra*

    E-Print Network [OSTI]

    Chopra, Harsh Deep

    , for example, magnetic-field sensors and read-heads in data- storage devices.11 A key impedimentNanostructural considerations in giant magnetoresistive Co-Cu-based symmetric spin valves Harsh, on the nanostructure and resulting giant magnetoresistive properties of symmetric spin valves of the type Ni

  14. 2006 Nature Publishing Group Artificial `spin ice' in a geometrically frustrated

    E-Print Network [OSTI]

    Chandra, Premi

    © 2006 Nature Publishing Group Artificial `spin ice' in a geometrically frustrated lattice positions in frozen water3­6 . Here we report an artificial geometrically frus- trated magnet based is strikingly similar to the low-temperature state of spin ice. These results demonstrate that artificial

  15. Surface sensitivity of the spin Seebeck effect

    SciTech Connect (OSTI)

    Aqeel, A.; Vera-Marun, I. J.; Wees, B. J. van; Palstra, T. T. M., E-mail: t.t.m.palstra@rug.nl [Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands)

    2014-10-21T23:59:59.000Z

    We have investigated the influence of the interface quality on the spin Seebeck effect (SSE) of the bilayer system yttrium iron garnet (YIG)–platinum (Pt). The magnitude and shape of the SSE is strongly influenced by mechanical treatment of the YIG single crystal surface. We observe that the saturation magnetic field (H{sub sat}{sup SSE}) for the SSE signal increases from 55.3?mT to 72.8?mT with mechanical treatment. The change in the magnitude of H{sub sat}{sup SSE} can be attributed to the presence of a perpendicular magnetic anisotropy due to the treatment induced surface strain or shape anisotropy in the Pt/YIG system. Our results show that the SSE is a powerful tool to investigate magnetic anisotropy at the interface.

  16. Hysteretic Optimization For Spin Glasses

    E-Print Network [OSTI]

    B. Goncalves; S. Boettcher

    2007-12-10T23:59:59.000Z

    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.

  17. Joule heating-induced coexisted spin Seebeck effect and spin Hall magnetoresistance in the platinum/Y{sub 3}Fe{sub 5}O{sub 12} structure

    SciTech Connect (OSTI)

    Wang, W. X. [State Key Laboratory of Advance Technology for Material Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wang, S. H.; Zou, L. K.; Cai, J. W.; Sun, J. R., E-mail: jrsun@iphy.ac.cn, E-mail: sun-zg@whut.edu.cn [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Sun, Z. G. [State Key Laboratory of Advance Technology for Material Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

    2014-11-03T23:59:59.000Z

    Spin Seebeck effect (SSE) and spin Hall magnetoresistance (SMR) are observed simultaneously in the Pt/Y{sub 3}Fe{sub 5}O{sub 12} hybrid structure when thermal gradient is produced by Joule heating. According to their dependences on applied current, these two effects can be separated. Their dependence on heating power and magnetic field is systematically studied. With the increase of heating power, the SSE enhances linearly, whereas the SMR decreases slowly. The origin of the spin currents is further analyzed. The heating power dependences of the spin currents associated with the SSE and the SMR are found to be different.

  18. Multiple-spin coherence transfer in linear Ising spin chains and beyond: numerically-optimized pulses and experiments

    E-Print Network [OSTI]

    Manoj Nimbalkar; Robert Zeier; Jorge L. Neves; S. Begam Elavarasi; Haidong Yuan; Navin Khaneja; Kavita Dorai; Steffen J. Glaser

    2011-10-24T23:59:59.000Z

    We study multiple-spin coherence transfers in linear Ising spin chains with nearest neighbor couplings. These constitute a model for efficient information transfers in future quantum computing devices and for many multi-dimensional experiments for the assignment of complex spectra in nuclear magnetic resonance spectroscopy. We complement prior analytic techniques for multiple-spin coherence transfers with a systematic numerical study where we obtain strong evidence that a certain analytically-motivated family of restricted controls is sufficient for time-optimality. In the case of a linear three-spin system, additional evidence suggests that prior analytic pulse sequences using this family of restricted controls are time-optimal even for arbitrary local controls. In addition, we compare the pulse sequences for linear Ising spin chains to pulse sequences for more realistic spin systems with additional long-range couplings between non-adjacent spins. We experimentally implement the derived pulse sequences in three and four spin systems and demonstrate that they are applicable in realistic settings under relaxation and experimental imperfections-in particular-by deriving broadband pulse sequences which are robust with respect to frequency offsets.

  19. Ultrafast reduction of the total magnetization in iron

    SciTech Connect (OSTI)

    Fognini, A., E-mail: afognini@phys.ethz.ch; Michlmayr, T. U.; Salvatella, G.; Vaterlaus, A.; Acremann, Y., E-mail: acremann@solid.phys.ethz.ch [Laboratory for Solid State Physics, Otto-Stern-Weg 1, ETH Zurich, 8093 Zurich (Switzerland); Wetli, C. [Multifunktionale Ferroische Mat., Vladimir-Prelog-Weg 1-5/10, ETH Zurich, 8093 Zurich (Switzerland); Ramsperger, U.; Bähler, T.; Pescia, D. [Laboratory for Solid State Physics, Auguste-Piccard-Hof 1, ETH Zurich, 8093 Zurich (Switzerland); Sorgenfrei, F.; Beye, M.; Eschenlohr, A.; Pontius, N.; Föhlisch, A. [Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin (Germany); Stamm, C. [Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin (Germany); Department of Materials, ETH Zurich, Hönggerbergring 64, 8093 Zurich (Switzerland); Hieke, F.; Dell'Angela, M.; Wurth, W. [Institut für Experimentalphysik and Center for Free-Electron Laser Science, Universität Hamburg, 22607 Hamburg (Germany); Jong, S. de; Dürr, H. A. [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); and others

    2014-01-20T23:59:59.000Z

    Surprisingly, if a ferromagnet is exposed to an ultrafast laser pulse, its apparent magnetization is reduced within less than a picosecond. Up to now, the total magnetization, i.e., the average spin polarization of the whole valence band, was not detectable on a sub-picosecond time scale. Here, we present experimental data, confirming the ultrafast reduction of the total magnetization. Soft x-ray pulses from the free electron laser in Hamburg (FLASH) extract polarized cascade photoelectrons from an iron layer excited by a femtosecond laser pulse. The spin polarization of the emitted electrons is detected by a Mott spin polarimeter.

  20. Magnetism and superconductivity in U?PtxRh(1–x)C?

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

    Wakeham, N.; Ni, Ni; Bauer, E. D.; Thompson, J. D.; Tegtmeier, E.; Ronning, F.

    2015-01-01T23:59:59.000Z

    We report the phase diagram of the doping series U?PtxRh(1–x)C?, studied through measurements of resistivity, specific heat, and magnetic susceptibility. The Néel temperature of U?Rh?C? of ~ 22 K is suppressed with increasing Pt content, reaching zero temperature close to x = 0.7, where we observed signatures of increased quantum fluctuations. In addition, evidence is presented that the antiferromagnetic state undergoes a spin-reorientation transition upon application of an applied magnetic field. This transition shows non-monotonic behavior as a function of x, peaking at around x = 0.3. Superconductivity is observed for x ? 0.9, with Tc increasing with increasing x.more »The reduction in Tc and increase in residual resistivity with decreasing Pt content is inconsistent with the extension of the Abrikosov-Gor'kov theory to unconventional superconductivity.« less

  1. Temperature dependence of magnetization and anisotropy in uniaxial NiFe{sub 2}O{sub 4} nanomagnets: Deviation from the Callen-Callen power law

    SciTech Connect (OSTI)

    Chatterjee, Biplab K.; Ghosh, C. K. [School of Materials Science and Nanotechnology, Jadavpur University, Jadavpur, Kolkata 700032 (India); Chattopadhyay, K. K., E-mail: kalyan-chattopadhyay@yahoo.com [School of Materials Science and Nanotechnology, Jadavpur University, Jadavpur, Kolkata 700032 (India); Thin Film and Nanoscience Laboratory, Department of Physics, Jadavpur University, Jadavpur, Kolkata 700032 (India)

    2014-10-21T23:59:59.000Z

    The thermal variation of magnetic anisotropy (K) and saturation magnetization (M{sub S}) for uniaxial nickel ferrite (NiFe{sub 2}O{sub 4}) nanomagnets are investigated. Major magnetic hysteresis loops are measured for the sample at temperatures over the range 5–280?K using a vibrating sample magnetometer. The high-field regimes of the hysteresis loops are modeled using the law of approach to saturation, based on the assumption that at sufficiently high field only direct rotation of spin-moment take place, with an additional forced magnetization term that is linear with applied field. The uniaxial anisotropy constant K is calculated from the fitting of the data to the theoretical equation. As temperature increases from 5?K to 280?K, a 49% reduction of K, accompanied by an 85% diminution of M{sub S} is observed. Remarkably, K is linearly proportional to M{sub S}{sup 2.6} in the whole temperature range violating the existing theoretical model by Callen and Callen. The unusual power-law behavior for the NiFe{sub 2}O{sub 4} uniaxial nanomagnets is ascribed to the non-negligible contributions from inter-sublattice pair interactions, Neel surface anisotropy, and higher order anisotropies. A complete realization of the unusual anisotropy-magnetization scaling behavior for nanoscale two-sublattice magnetic materials require a major modification of the existing theory by considering the exact mechanism of each contributions to the effective anisotropy.

  2. Spin-orbit couplings between distant electrons trapped individually on liquid helium

    E-Print Network [OSTI]

    Miao Zhang; L. F. Wei

    2012-11-13T23:59:59.000Z

    We propose an approach to entangle spins of electrons floating on liquid helium by coherently manipulating their spin-orbit interactions. The configuration consists of single electrons, confined individually on liquid helium by the microelectrodes, moving along the surface as the harmonic oscillators. It has been known that the spin of an electron could be coupled to its orbit (i.e., the vibrational motion) by properly applying a magnetic field. Based on this single electron spin-orbit coupling, here we show that a Jaynes-Cummings (JC) type interaction between the spin of an electron and the orbit of another electron at a distance could be realized via the strong Coulomb interaction between the electrons. Consequently, the proposed JC interaction could be utilized to realize a strong orbit-mediated spin-spin coupling and implement the desirable quantum information processing between the distant electrons trapped individually on liquid helium.

  3. Generation of spin-polarized currents via cross-relaxation with dynamically pumped paramagnetic impurities

    SciTech Connect (OSTI)

    Meriles, Carlos A. [Department of Physics, CUNY-City College of New York, New York, New York 10031 (United States); Doherty, Marcus W. [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

    2014-07-14T23:59:59.000Z

    Key to future spintronics and spin-based information processing technologies is the generation, manipulation, and detection of spin polarization in a solid state platform. Here, we theoretically explore an alternative route to spin injection via the use of dynamically polarized nitrogen-vacancy (NV) centers in diamond. We focus on the geometry where carriers and NV centers are confined to proximate, parallel layers and use a “trap-and-release” model to calculate the spin cross-relaxation probabilities between the charge carriers and neighboring NV centers. We identify near-unity regimes of carrier polarization depending on the NV spin state, applied magnetic field, and carrier g-factor. In particular, we find that unlike holes, electron spins are distinctively robust against spin-lattice relaxation by other, unpolarized paramagnetic centers. Further, the polarization process is only weakly dependent on the carrier hopping dynamics, which makes this approach potentially applicable over a broad range of temperatures.

  4. Algebraic spin liquid in an exactly solvable spin model

    SciTech Connect (OSTI)

    Yao, Hong; Zhang, Shou-Cheng; Kivelson, Steven A.; /Stanford U., Phys. Dept.

    2010-03-25T23:59:59.000Z

    We have proposed an exactly solvable quantum spin-3/2 model on a square lattice. Its ground state is a quantum spin liquid with a half integer spin per unit cell. The fermionic excitations are gapless with a linear dispersion, while the topological 'vison' excitations are gapped. Moreover, the massless Dirac fermions are stable. Thus, this model is, to the best of our knowledge, the first exactly solvable model of half-integer spins whose ground state is an 'algebraic spin liquid.'

  5. Fast deterministic switching in orthogonal spin torque devices via the control of the relative spin polarizations

    SciTech Connect (OSTI)

    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

    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.

  6. Spin interference of holes in silicon nanosandwiches

    SciTech Connect (OSTI)

    Bagraev, N. T., E-mail: Bagraev@mail.ioffe.ru; Danilovskii, E. Yu.; Klyachkin, L. E.; Malyarenko, A. M. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Mashkov, V. A. [St. Petersburg State Polytechnical University (Russian Federation)

    2012-01-15T23:59:59.000Z

    Spin-dependent transport of holes is studied in silicon nanosandwiches on an n-Si (100) surface which are represented by ultranarrow p-Si quantum wells confined by {delta}-barriers heavily doped with boron. The measurement data of the longitudinal and Hall voltages as functions of the top gate voltage without an external magnetic field show the presence of edge conduction channels in the silicon nanosandwiches. An increase in the stabilized source-drain current within the range 0.25-5 nA subsequently exhibits the longitudinal conductance value 4e{sup 2}/h, caused by the contribution of the multiple Andreev reflection, the value 0.7(2e{sup 2}/h) corresponding to the known quantum conductance staircase feature, and displays Aharonov-Casher oscillations, which are indicative of the spin polarization of holes in the edge channels. In addition, at a low stabilized source-drain current, due to spin polarization, a nonzero Hall voltage is detected which is dependent on the top gate voltage; i. e., the quantum spin Hall effect is observed. The measured longitudinal I-V characteristics demonstrate Fiske steps and a negative differential resistance caused by the generation of electromagnetic radiation as a result of the Josephson effect. The results obtained are explained within a model of topological edge states which are a system of superconducting channels containing quantum point contacts transformable to single Josephson junctions at an increasing stabilized source-drain current.

  7. Investigation of wettability by NMR microscopy and spin-lattice relaxation

    SciTech Connect (OSTI)

    Doughty, D.A.; Tomutsa, Liviu

    1993-11-01T23:59:59.000Z

    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.

  8. Unified Description of Bulk and Interface-Enhanced Spin Pumping S. M. Watts, J. Grollier,* C. H. van der Wal, and B. J. van Wees

    E-Print Network [OSTI]

    van der Wal, Caspar H.

    Unified Description of Bulk and Interface-Enhanced Spin Pumping S. M. Watts, J. Grollier,* C. H in semiconductors or metals by rf magnetic field pumping. With a semiclassical model we show that a rotating applied dynamics of a ferromagnetic electrode into or out of which the spin currents flow. In spin-pumping devices

  9. The spin deep within

    SciTech Connect (OSTI)

    Stackhouse, S. (Michigan)

    2008-10-08T23:59:59.000Z

    The electronic configuration of iron impurities in lower-mantle minerals influences their physical properties, but it is not well constrained. New studies suggest that ferrous iron in silicate phases exists mainly in an intermediate spin state.

  10. Electron Spin Precession for the Time Fractional Pauli Equation

    E-Print Network [OSTI]

    Hosein Nasrolahpour

    2011-04-05T23:59:59.000Z

    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.

  11. Pressure-induced magnetic, structural, and electronic phase transitions in LaFeO{sub 3}: A density functional theory (generalized gradient approximation)?+?U study

    SciTech Connect (OSTI)

    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 [EMMG, Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)

    2014-07-14T23:59:59.000Z

    We have investigated the behavior of orthoferrite LaFeO{sub 3} at ambient conditions and under pressure using DFT (generalized gradient approximation (GGA))?+?U approach. Ground state electronic (band gap) and magnetic properties are considerably improved due to the Hubbard correction. Moreover, the experimentally observed pressure-driven phase transition, namely, the simultaneous occurrence of spin crossover, isostructural volume collapse, and drastic reduction in electrical resistance (electronic phase transition) is nicely described by GGA?+?U calculations. In particular, despite a sharp drop in resistance, a small band gap still remains in the low spin state indicating an insulator to semiconductor phase transition, in good agreement with the experiments but in contrast to GGA, which predicts metallic behavior in low spin state. We discuss the origin of variation in electronic structure of LaFeO{sub 3} in low spin state as obtained from GGA to GGA?+?U methods. These results emphasize the importance of correlation effects in describing the pressure-driven phase transition in LaFeO{sub 3} and other rare-earth orthoferrites.

  12. Quantum Model Of Spin Noise

    E-Print Network [OSTI]

    R. Annabestani; D. G. Cory; J. Emerson

    2015-03-03T23:59:59.000Z

    Any ensemble of quantum particles exhibits statistical fluctuations known as spin noise. Here, we provide a description of spin noise in the language of open quantum systems. The description unifies the signatures of spin noise under both strong and weak measurements. Further, the model accounts for arbitrary spin dynamics from an arbitrary initial state. In all cases we can find both the spin noise and its time correlation function.

  13. Investigations of the electronic and magnetic structures of Co{sub 2}YGa (Y=Cr, Mn) Heusler alloys and their (100) surfaces

    SciTech Connect (OSTI)

    Hamad, Bothina, E-mail: b.hamad@ju.edu.jo [Physics Department, The University of Jordan, Amman-11942 (Jordan)

    2014-03-21T23:59:59.000Z

    Density functional theory calculations are performed to investigate the structural, electronic, and magnetic properties of bulk structures of Co{sub 2}YGa (Y?=?Cr, Mn) Heusler alloys and the surfaces along the (100) orientation. The bulk structures of both alloys show a ferromagnetic behavior with total magnetic moments of 3.03?{sub B} and 4.09?{sub B} and high spin polarizations of 99% and 67% for Co{sub 2}CrGa and Co{sub 2}MnGa, respectively. The surfaces are found to exhibit corrugations due to different relaxations of the surface atoms. For the case of Co{sub 2}CrGa, two surfaces preserve the half metallicity, namely those with Cr-Ga and Ga– terminations with high spin polarizations above 90%, whereas it dropped to about 50% for the other surfaces. However, the spin polarizations of Co-Co and Mn-Ga terminated surfaces remain close to that of bulk Co{sub 2}MnGa alloy, whereas it is suppressed down to 17% for Co– termination. The highest local magnetic moments are found to be 3.26??{sub B} and 4.11??{sub B} for Cr and Mn surface atoms in Cr-Ga and Mn– terminated surfaces, respectively.

  14. Frustration and Entanglement in Compass and Spin-Orbital Models

    E-Print Network [OSTI]

    Andrzej M. Ole?

    2014-10-24T23:59:59.000Z

    We review the consequences of intrinsic frustration of the orbital superexchange and of spin-orbital entanglement. While Heisenberg perturbing interactions remove frustration in the compass model, the lowest columnar excitations are robust in the nanoscopic compass clusters and might be used for quantum computations. Entangled spin-orbital states determine the ground states in some cases, while in others concern excited states and lead to measurable consequences, as in the $R$VO$_3$ perovskites. On-site entanglement for strong spin-orbit coupling generates the frustrated Kitaev-Heisenberg model with a rich magnetic phase diagram on the honeycomb lattice. Frustration is here reflected in hole propagation which changes from coherent in an antiferromagnet via hidden quasiparticles in zigzag and stripe phases to entirely incoherent one in the Kitaev spin liquid.

  15. Spin relaxation time dependence on optical pumping intensity in GaAs:Mn

    SciTech Connect (OSTI)

    Burobina, V. [Department of Physics and Astronomy, University of Utah, 115 South 1400 East, Salt Lake City, Utah 84112-0830 (United States); Binek, Ch. [Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, Theodore Jorgensen Hall, 855 North 16th Street, University of Nebraska, P.O. Box 880299, Lincoln, Nebraska 68588-0299 (United States)

    2014-04-28T23:59:59.000Z

    We analyze the dependence of electron spin relaxation time on optical pumping intensity in a partially compensated acceptor semiconductor GaAs:Mn using analytic solutions for the kinetic equations of the charge carrier concentrations. Our results are applied to previous experimental data of spin-relaxation time vs. excitation power for magnetic concentrations of approximately 10{sup 17}?cm{sup ?3}. The agreement of our analytic solutions with the experimental data supports the mechanism of the earlier-reported atypically long electron-spin relaxation time in the magnetic semiconductor.

  16. Thermal entanglement of spins in mean-field clusters

    SciTech Connect (OSTI)

    Asoudeh, M.; Karimipour, V. [Department of Physics, Sharif University of Technology, P.O. Box 11365-9161, Tehran (Iran, Islamic Republic of)

    2006-06-15T23:59:59.000Z

    We determine thermal entanglement in mean-field clusters of N spin one-half particles interacting via the anisotropic Heisenberg interaction, with and without external magnetic field. For the xxx cluster in the absence of magnetic field we prove that only the N=2 ferromagnetic cluster shows entanglement. An external magnetic field B can only entangle xxx antiferromagnetic clusters in certain regions of the B-T plane. On the other hand, the xxz clusters of size N>2 are entangled only when the interaction is ferromagnetic. Detailed dependence of the entanglement on various parameters is investigated in each case.

  17. k-space spin filtering effect in the epitaxial Fe/Au/Fe/GaAs(001) spin-valve

    SciTech Connect (OSTI)

    Hervé, M.; Tricot, S.; Claveau, Y.; Delhaye, G.; Lépine, B.; Di Matteo, S.; Schieffer, P.; Turban, P., E-mail: pascal.turban@univ-rennes1.fr [Département Matériaux et Nanosciences, Institut de Physique de Rennes, UMR 6251, CNRS-Université de Rennes 1, Campus de Beaulieu, Bât 11E, 35042 Rennes cedex (France)

    2013-11-11T23:59:59.000Z

    The hot-electron magnetotransport of epitaxial Fe/Au/Fe/GaAs(001) spin-valves is investigated by ballistic-electron magnetic microscopy. A magnetocurrent amplitude larger than 500% is observed at room temperature close to the Schottky barrier energy. Remarkably, this magnetocurrent is not significantly affected by the thickness reduction of ferromagnetic films, down to 5 atomic layers of the Fe(001) top electrode. This rather suggests a dominant interfacial spin-filtering effect. Finally, the magnetocurrent is strongly reduced when the effective mass of the semiconductor collector is increased. These observations are consistent with recent theoretical prediction of k-space spin-filtering effect in epitaxial spin-valves attached to a semiconducting lead.

  18. Y-shape spin-separator for two-dimensional group-IV nanoribbons based on quantum spin hall effect

    SciTech Connect (OSTI)

    Gupta, Gaurav, E-mail: a0089293@nus.edu.sg; Abdul Jalil, Mansoor Bin; Liang, Gengchiau, E-mail: elelg@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Lin, Hsin [Graphene Research Centre and Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Bansil, Arun [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States); Huang, Cheng-Yi; Tsai, Wei-Feng [Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China)

    2014-01-20T23:59:59.000Z

    An efficient spin-separator that operates in quantum spin hall phase has been investigated for two-dimensional group-IV materials. A three-terminal Y-shaped device has been simulated via non-equilibrium Green Function to demonstrate the separation of unpolarized current at source terminal into spin-polarized current of opposite polarity at the two drain terminals. Device controls, i.e., tunable buckling and perpendicular magnetic field have been modeled comprehensively to evaluate the device feasibility and performance. It is shown that these controls can preferentially steer current between the two drains to create a differential charge current with complementary spin polarization, thus enabling a convenient regulation of output signal.

  19. A standard format and a graphical user interface for spin system specification

    E-Print Network [OSTI]

    A. G. Biternas; G. T. P. Charnock; Ilya Kuprov

    2013-11-22T23:59:59.000Z

    We introduce a simple and general XML format for spin system description that is the result of extensive consultations within Magnetic Resonance community and unifies under one roof all major existing spin interaction specification conventions. The format is human-readable, easy to edit and easy to parse using standard XML libraries. We also describe a graphical user interface that was designed to facilitate construction and visualization of complicated spin systems. The interface is capable of generating input files for several popular spin dynamics simulation packages.

  20. A standard format and a graphical user interface for spin system specification

    E-Print Network [OSTI]

    Biternas, A G; Kuprov, Ilya

    2013-01-01T23:59:59.000Z

    We introduce a simple and general XML format for spin system description that is the result of extensive consultations within Magnetic Resonance community and unifies under one roof all major existing spin interaction specification conventions. The format is human-readable, easy to edit and easy to parse using standard XML libraries. We also describe a graphical user interface that was designed to facilitate construction and visualization of complicated spin systems. The interface is capable of generating input files for several popular spin dynamics simulation packages.

  1. Search for a coupling of the Earth's gravitational field to nuclear spins in atomic mercury

    SciTech Connect (OSTI)

    Venema, B.J.; Majumder, P.K.; Lamoreaux, S.K.; Heckel, B.R.; Fortson, E.N. (Department of Physics, FM-15, University of Washington, Seattle, Washington 98195 (United States))

    1992-01-13T23:59:59.000Z

    We have measured the ratio of nuclear spin-precession frequencies of {sup 199}Hg and {sup 201}Hg atoms for two orientations of magnetic field relative to the Earth's gravitational field. We find that the spin-dependent component of gravitational energy is less than 2.2{times}10{sup {minus}21} eV, a substantial improvement over previous limits. Our result provides a test of the equivalence principle for nuclear spins, and sets limits on the magnitude of possible scalar-pseudoscalar interactions which would couple to the spins.

  2. arch magnetic resonance: Topics by E-print Network

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

    created by the spins in the sample Cai, Long 2 Laboratory Simulation of Arched Magnetic Flux Rope Eruptions in the Solar Atmosphere S. K. P. Tripathi* and W. Gekelman Plasma...

  3. Ferrofluid surface and volume flows in uniform rotating magnetic fields

    E-Print Network [OSTI]

    Elborai, Shihab M. (Shihab Mahmoud), 1977-

    2006-01-01T23:59:59.000Z

    Ferrofluid surface and volume effects in uniform dc and rotating magnetic fields are studied. Theory and corroborating measurements are presented for meniscus shapes and resulting surface driven flows, spin-up flows, and ...

  4. Tuning the Thermal Properties of Magnetic Tunnel Junctions

    E-Print Network [OSTI]

    Amin, Vivek Pravin

    2014-04-18T23:59:59.000Z

    magnetic field. This phenomenon potentially enables the controlled manipulation of temperature gradients, the recycling of wasted heat, and thermal spin-logic. Our calculations employ the Landauer-Buttiker scattering formalism, in conjunction...

  5. artery magnetic resonance: Topics by E-print Network

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

    10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Next Page Last Page Topic Index 1 Whole Brain Isotropic Arterial Spin Labeling Magnetic Resonance Imaging in a transgenic mouse...

  6. Resonant control of spins in the quasi-one-dimensional channel by interplay of confinement and Zeeman splitting

    SciTech Connect (OSTI)

    Berman, D. H.; Khodas, M.; Flatté, M. E. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)

    2014-10-15T23:59:59.000Z

    We study the spin transport in a quasi-one-dimensional channel defined in a two-dimensional electron gas. The combined action of geometrical confinement and the spin precession is analyzed. We demonstrate that for certain orientations of the in-plane magnetic field and for specific range of its magnitude the spin polarization exhibits a strong decrease referred to as ballistic spin resonance (BSR). The phenomenon is due to the commensuration of the Zeeman and inter-subband energy splitting. We show that the BSR requires a finite spin-orbit (SO) interaction although the condition for the BSR onset is independent on SO coupling.

  7. Maximal spin and energy conversion efficiency in a symbiotic system of black hole, disk and jet

    E-Print Network [OSTI]

    Zoltán Kovács; László Á. Gergely; Peter L. Biermann

    2011-10-13T23:59:59.000Z

    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.

  8. Thermoelectric probe for Rashba spin-orbit interaction strength in a two dimensional electron gas

    E-Print Network [OSTI]

    S. K. Firoz Islam; Tarun Kanti Ghosh

    2012-07-18T23:59:59.000Z

    Thermoelectric coefficients of a two dimensional electron gas with the Rashba spin-orbit interaction are presented here. In absence of magnetic field, thermoelectric coefficients are enhanced due to the Rashba spin-orbit interaction. In presence of magnetic field, the thermoelectric coefficients of spin-up and spin-down electrons oscillate with different frequency and produces beating patterns in the components of the total thermoelectric power and the total thermal conductivity. We also provide analytical expressions of the thermoelectric coefficients to explain the beating pattern formation. We obtain a simple relation which determines the Rashba SOI strength if the magnetic fields corresponding to any two successive beat nodes are known from the experiment.

  9. Thermoelectric probe for Rashba spin-orbit interaction strength in a two dimensional electron gas

    E-Print Network [OSTI]

    Islam, S K Firoz

    2012-01-01T23:59:59.000Z

    Thermoelectric coefficients of a two dimensional electron gas with the Rashba spin-orbit interaction are presented here. In absence of magnetic field, thermoelectric coefficients are enhanced due to the Rashba spin-orbit interaction. In presence of magnetic field, the thermoelectric coefficients of spin-up and spin-down electrons oscillate with different frequency and produces beating patterns in the components of the total thermoelectric power and the total thermal conductivity. We also provide analytical expressions of the thermoelectric coefficients to explain the beating pattern formation. We obtain a simple relation which determines the Rashba SOI strength if the magnetic fields corresponding to any two successive beat nodes are known from the experiment.

  10. Incorporation of 4d and 5d Transition Metal Cyanometallates into Magnetic Clusters and Materials.

    E-Print Network [OSTI]

    Hilfiger, Matthew Gary

    2011-08-08T23:59:59.000Z

    scenarios: (a) A ferromagnet where neighboring spins align in a parallel fashion with the magnetic field and retain their directionality even when the field is removed; (b) An antiferromagnet wherein the spins of neighboring centers couple... scheme of Prussian Blue analogs, M' = V,Cr, Fe, Co, M = V, Cr, Mn, Fe, Ni , L = labile ligand or solvent molecule. 6 cancel, and the remaining unpaired spins align with the field as a ferromagnet does (Scheme 2a). Although these magnetic...

  11. 1 One-Dimensional Magnetism Hans-Jurgen Mikeska1

    E-Print Network [OSTI]

    Dragon, Norbert

    for S=1/2 and biquadratic exchange for S=1 systems), with spin-orbital models and mixed spin in the critical and ordered phases. 1.1 Introduction The field of low-dimensional magnetism can be traced back of today's solid state physics. For the first 40 years this was an exclusively theoretical field. Theo

  12. Hyperpolarized Nanodiamond with Long Spin Relaxation Times

    E-Print Network [OSTI]

    Ewa Rej; Torsten Gaebel; Thomas Boele; David E. J. Waddington; David J. Reilly

    2015-02-22T23:59:59.000Z

    The use of hyperpolarized agents in magnetic resonance (MR), such as 13C-labeled compounds, enables powerful new imaging and detection modalities that stem from a 10,000-fold boost in signal. A major challenge for the future of the hyperpolarizaton technique is the inherently short spin relaxation times, typically solid-state environment, exhibit relaxation times exceeding 1 hour. Combined with the already established applications of NDs in the life-sciences as inexpensive fluorescent markers and non-cytotoxic substrates for gene and drug delivery, these results extend the theranostic capabilities of nanoscale diamonds into the domain of hyperpolarized MR.

  13. Many-body Interactions in Magnetic Films and Nanostructures

    SciTech Connect (OSTI)

    Stephen D. Kevan

    2012-12-12T23:59:59.000Z

    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.

  14. Spin-dependent band structure, Fermi surface, and carrier lifetime of permalloy

    E-Print Network [OSTI]

    Himpsel, Franz J.

    -6951 98 01249-2 Permalloy is one of the most common materials in mag- netic data storage and can be found in a variety of magnetic micro- and nanostructures.1 Several useful properties come together to make permalloy that are responsible for spin trans- port in 3d transition metals.1,11 They are crucial for magnetic devices

  15. Spinning fluids reactor

    SciTech Connect (OSTI)

    Miller, Jan D; Hupka, Jan; Aranowski, Robert

    2012-11-20T23:59:59.000Z

    A spinning fluids reactor, includes a reactor body (24) having a circular cross-section and a fluid contactor screen (26) within the reactor body (24). The fluid contactor screen (26) having a plurality of apertures and a circular cross-section concentric with the reactor body (24) for a length thus forming an inner volume (28) bound by the fluid contactor screen (26) and an outer volume (30) bound by the reactor body (24) and the fluid contactor screen (26). A primary inlet (20) can be operatively connected to the reactor body (24) and can be configured to produce flow-through first spinning flow of a first fluid within the inner volume (28). A secondary inlet (22) can similarly be operatively connected to the reactor body (24) and can be configured to produce a second flow of a second fluid within the outer volume (30) which is optionally spinning.

  16. Spin Physics at COMPASS

    E-Print Network [OSTI]

    C. Schill; for the COMPASS collaboration

    2012-01-02T23:59:59.000Z

    The COMPASS experiment is a fixed target experiment at the CERN SPS using muon and hadron beams for the investigation of the spin structure of the nucleon and hadron spectroscopy. The main objective of the muon physics program is the study of the spin of the nucleon in terms of its constituents, quarks and gluons. COMPASS has accumulated data during 6 years scattering polarized muons off a longitudinally or a transversely polarized deuteron (6LiD) or proton (NH3) target. Results for the gluon polarization are obtained from longitudinal double spin cross section asymmetries using two different channels, open charm production and high transverse momentum hadron pairs, both proceeding through the photon-gluon fusion process. Also, the longitudinal spin structure functions of the proton and the deuteron were measured in parallel as well as the helicity distributions for the three lightest quark flavors. With a transversely polarized target, results were obtained with proton and deuteron targets for the Collins and Sivers asymmetries for charged hadrons as well as for identified kaons and pions. The Collins asymmetry is sensitive to the transverse spin structure of the nucleon, while the Sivers asymmetry reflects correlations between the quark transverse momentum and the nucleon spin. Recently, a new proposal for the COMPASS II experiment was accepted by the CERN SPS which includes two new topics: Exclusive reactions like DVCS and DVMP using the muon beam and a hydrogen target to study generalized parton distributions and Drell-Yan measurements using a pion beam and a polarized NH3 target to study transverse momentum dependent distributions.

  17. Note on the helicity decomposition of spin and orbital optical currents

    E-Print Network [OSTI]

    Aiello, Andrea

    2015-01-01T23:59:59.000Z

    In the helicity representation, the Poynting vector (current) for a monochromatic optical field, when calculated using either the electric or the magnetic field, separates into right-handed and left-handed contributions, with no cross-helicity contributions. Cross-helicity terms do appear in the orbital and spin contributions to the current. But when the electric and magnetic formulas are averaged ('electric-magnetic democracy'), these terms cancel, restoring the separation into right-handed and left-handed currents for orbital and spin separately.

  18. Magnetism and superconductivity in U?PtxRh(1–x)C?

    SciTech Connect (OSTI)

    Wakeham, N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ni, Ni [Univ. of California, Los Angeles, CA (United States); Bauer, E. D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Thompson, J. D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tegtmeier, E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ronning, F. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-01-01T23:59:59.000Z

    We report the phase diagram of the doping series U?PtxRh(1–x)C?, studied through measurements of resistivity, specific heat, and magnetic susceptibility. The Néel temperature of U?Rh?C? of ~ 22 K is suppressed with increasing Pt content, reaching zero temperature close to x = 0.7, where we observed signatures of increased quantum fluctuations. In addition, evidence is presented that the antiferromagnetic state undergoes a spin-reorientation transition upon application of an applied magnetic field. This transition shows non-monotonic behavior as a function of x, peaking at around x = 0.3. Superconductivity is observed for x ? 0.9, with Tc increasing with increasing x. The reduction in Tc and increase in residual resistivity with decreasing Pt content is inconsistent with the extension of the Abrikosov-Gor'kov theory to unconventional superconductivity.

  19. Spin-torque diode radio-frequency detector with voltage tuned resonance

    SciTech Connect (OSTI)

    Skowro?ski, Witold, E-mail: skowron@agh.edu.pl; Frankowski, Marek; Stobiecki, Tomasz [AGH University of Science and Technology, Department of Electronics, Al. Mickiewicza 30, 30-059 Kraków (Poland); Wrona, Jerzy [AGH University of Science and Technology, Department of Electronics, Al. Mickiewicza 30, 30-059 Kraków (Poland); Singulus Technologies, Kahl am Main 63796 (Germany); Ogrodnik, Piotr [Faculty of Physics, Warsaw University of Technology, ul. Koszykowa 75, 00-662 Warsaw (Poland); AGH University of Science and Technology, Department of Electronics, Al. Mickiewicza 30, 30-059 Kraków (Poland); Barna?, Józef [Faculty of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Pozna? (Poland); Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Pozna? (Poland)

    2014-08-18T23:59:59.000Z

    We report on a voltage-tunable radio-frequency (RF) detector based on a magnetic tunnel junction (MTJ). The spin-torque diode effect is used to excite and/or detect RF oscillations in the magnetic free layer of the MTJ. In order to reduce the overall in-plane magnetic anisotropy of the free layer, we take advantage of the perpendicular magnetic anisotropy at the interface between ferromagnetic and insulating layers. The applied bias voltage is shown to have a significant influence on the magnetic anisotropy, and thus on the resonance frequency of the device. This influence also depends on the voltage polarity. The obtained results are accounted for in terms of the interplay of spin-transfer-torque and voltage-controlled magnetic anisotropy effects.

  20. Study of spatial spin-modulated structures by Mössbauer spectroscopy using SpectrRelax

    SciTech Connect (OSTI)

    Matsnev, Mikhail E., E-mail: mail@haali.su; Rusakov, Vyacheslav S., E-mail: mail@haali.su [M.V. Lomonosov Moscow State University, Physics Department, Leninskie gory, 119991 Moscow (Russian Federation)

    2014-10-27T23:59:59.000Z

    SpectrRelax is an application for analysis and fitting of absorption and emission Mössbauer spectra. It includes a large selection of static and relaxation spectrum models, and allows fitting and searching for optimal model parameters. Recently, we have added new models for Mössbauer spectra of nuclides in spatial spin modulated structures. In these structures, spin density or direction changes in a periodic way along a single direction, and this wave is incommensurate with the underlying lattice. The models include Spin/Charge density wave, where the shape of this wave is represented as a sum of odd harmonics, Anharmonic spin modulation where the spin direction has a cycloidal type modulation, and a Spiral-like spin structure, in which magnetic moments rotate in a plane perpendicular to the wave propagation vector, forming a spiral.

  1. Spin Precession and Quantum Vacuum

    E-Print Network [OSTI]

    F. Kheirandish; M. Amooshahi

    2005-09-18T23:59:59.000Z

    The effect of quantum vacuum on spin precession is investigated. The radiation reaction is obtained and the time of spin flip (up state to down state) or spontaneous decay, is calculated.

  2. Geometric phase of a central spin coupled to an antiferromagnetic environment

    E-Print Network [OSTI]

    Xiao-Zhong Yuan; Hsi-Sheng Goan; Ka-Di Zhu

    2010-03-05T23:59:59.000Z

    Using the spin-wave approximation, we study the geometric phase (GP) of a central spin (signal qubit) coupled to an antiferromagnetic (AF) environment under the application of an external global magnetic field. The external magnetic field affects the GP of the qubit directly and also indirectly through its effect on the AF environment. We find that when the applied magnetic field is increased to the critical magnetic field point, the AF environment undergoes a spin-flop transition, a first-order phase transition, and at the same time the GP of the qubit changes abruptly to zero. This sensitive change of the GP of a signal qubit to the parameter change of a many-body environment near its critical point may serve as another efficient tool or witness to study the many-body phase transition. The influences of the AF environment temperature and crystal anisotropy field on the GP are also investigated.

  3. Spin effect on parametric interactions of waves in magnetoplasmas

    SciTech Connect (OSTI)

    Shahid, M. [Department of Physics, Government College University, Lahore-54000 (Pakistan); Salam Chair in Physics, Government College University, Lahore-54000 (Pakistan); Melrose, D. B. [School of Physics, University of Sydney, New South Wales 2006 (Australia); Jamil, M. [Department of Physics, Government College University, Faisalabad-38000 (Pakistan); Murtaza, G. [Salam Chair in Physics, Government College University, Lahore-54000 (Pakistan)

    2012-11-15T23:59:59.000Z

    The parametric decay instability of upper hybrid wave into low-frequency electromagnetic Shear Alfven wave and Ordinary mode radiation (O-mode) has been investigated in an electron-ion plasma immersed in the uniform external magnetic field. Incorporating quantum effect due to electron spin, the fluid model has been used to investigate the linear and nonlinear response of the plasma species for three-wave coupling in a magnetoplasma. It is shown that the spin of electrons has considerable effect on the parametric decay of upper hybrid wave into Ordinary mode radiation (O-mode) and Shear Alfven wave even in classical regime.

  4. Structural disorder versus spin canting in monodisperse maghemite nanocrystals

    SciTech Connect (OSTI)

    Kubickova, S.; Vejpravova, J., E-mail: vejpravo@fzu.cz [Department of Magnetic Nanosystems, Institute of Physics of the ASCR, v.v.i., Na Slovance 2, 182 21 Prague (Czech Republic); Niznansky, D. [Faculty of Science, Department of Inorganic Chemistry, Charles University in Prague, Albertov 2030, 128 40 Prague (Czech Republic); Morales Herrero, M. P. [Instituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana Ins de la Cruz 3, Campus de Cantoblanco, 28049 Madrid (Spain); Salas, G. [Instituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana Ins de la Cruz 3, Campus de Cantoblanco, 28049 Madrid (Spain); Instituto Madrileno de Estudios Avanzados en Nanociencia, Campus Universitario de Cantoblanco, 28049 Madrid (Spain)

    2014-06-02T23:59:59.000Z

    Monodisperse maghemite nanoparticles with diameter ranging from 7 to 20?nm were examined by the In-field Mössbauer Spectroscopy (IFMS) in varying external magnetic field up to 6 T. Surprisingly, the small-sized particles (7?nm) exhibit nearly no spin canting in contrast to the larger particles with lower surface-to-volume ratio. We demonstrate that the observed phenomenon is originated by lower relative crystallinity of the larger particles with different internal structure. Hence, the persistence of the 2nd and 5th absorption lines in the IFMS cannot be unambiguously assigned to the surface spins.

  5. Hole Spin Pumping and Re-pumping in a p-type ?-doped InAs Quantum Dot

    E-Print Network [OSTI]

    Konstantinos G. Lagoudakis; Kevin A. Fischer; Tomas Sarmiento; Kai Mueller; Jelena Vu?kovi?

    2014-08-29T23:59:59.000Z

    We have grown high quality p-type {\\delta}-doped InAs quantum dots and have demonstrated coherent spin pumping and repumping of a hole spin in a positively charged quantum dot by means of a single-laser driving scheme under a high magnetic field in the Voigt configuration. Modeling of our system shows excellent qualitative agreement with the experimental findings and further explores the performance of the single-laser scheme for spin pumping and re-pumping.

  6. TRANSVERSITY SINGLE SPIN ASYMMETRIES.

    SciTech Connect (OSTI)

    BOER,D.

    2001-04-27T23:59:59.000Z

    The theoretical aspects of two leading twist transversity single spin asymmetries, one arising from the Collins effect and one from the interference fragmentation functions, are reviewed. Issues of factorization, evolution and Sudakov factors for the relevant observables are discussed. These theoretical considerations pinpoint the most realistic scenarios towards measurements of transversity.

  7. ACCELERATION INDUCED SPIN AND

    E-Print Network [OSTI]

    Gerlach, Ulrich

    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

  8. Gluonic Spin Contribution to Proton Spin at NLO

    SciTech Connect (OSTI)

    Casey, Andrew [CSSM, School of Chemistry and Physics, University of Adelaide, Adelaide SA 5005 (Australia)

    2011-05-24T23:59:59.000Z

    In 1988, when the EMC results showed that the quarks had a much smaller contribution to the spin of the proton than previously thought, the 'Proton Spin Crisis' began. Since then, considerable effort has been directed into discovering the main contributors to proton spin and how much each contributes. One such contributor is the gluonic spin component. QCD NLO evolution equations are combined with boundary conditions obtained from heavy quark decoupling expressions to evolve the equations from infinity to the mass of the charm quark in order to determine the gluonic spin contribution.

  9. Information Transfer Fidelity in Networks of Spins

    E-Print Network [OSTI]

    Edmond Jonckheere; Frank Langbein; Sophie Schirmer

    2014-10-05T23:59:59.000Z

    Networks of spins, or spintronic networks, are given an Information Transfer Fidelity (ITF) derived from an upper bound on the probability of transmission of the excitation from one spin to another. It is shown that this theoretical bound can be reached asymptotically in time under certain conditions. The process of achieving maximum transfer probability is given a dynamical model, the translation on the torus, and the time to reach the maximum probability is estimated using the simultaneous Diophantine approximation computationally implemented using a variant of the Lenstra-Lenstra-Lov\\'asz (LLL) algorithm. The ITF induces a prametric on the network. For a ring with homogeneous couplings, it is shown that this prametric satisfies the triangle inequality, opening up the road to an ITF geometry, which turns out to be completely different from the geometry of the physical arrangement of the spin in the spintronic device. It is shown that transfer fidelities and transfer times can be improved by means of simple controls taking the form of strong localized magnetic fields, opening up the possibility for intelligent design of spintronic networks and dynamic routing of information encoded in such networks. The approach is much more flexible than engineering the couplings to favor some transfers.

  10. Ultrafast thermally induced magnetic switching in synthetic ferrimagnets

    SciTech Connect (OSTI)

    Evans, Richard F. L., E-mail: richard.evans@york.ac.uk; Ostler, Thomas A.; Chantrell, Roy W. [Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); Radu, Ilie [Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin (Germany); Rasing, Theo [Radboud University, Institute for Molecules and Materials, Heyendaalsewg 135, 6525 AJ Nijmegen (Netherlands)

    2014-02-24T23:59:59.000Z

    Synthetic ferrimagnets are composite magnetic structures formed from two or more anti-ferromagnetically coupled magnetic sublattices with different magnetic moments. Here, we report on atomistic spin simulations of the laser-induced magnetization dynamics on such synthetic ferrimagnets and demonstrate that the application of ultrashort laser pulses leads to sub-picosecond magnetization dynamics and all-optical switching in a similar manner as in ferrimagnetic alloys. Moreover, we present the essential material properties for successful laser-induced switching, demonstrating the feasibility of using a synthetic ferrimagnet as a high density magnetic storage element without the need of a write field.

  11. Electric control of magnetization relaxation in thin film ferromagnetic insulators.

    SciTech Connect (OSTI)

    Wang, Z.; Sun, Y.; Song, Y-Y.; Wu, M.; Schultheib, H.; Pearson, J. E.; Hoffmann, A. (Materials Science Division); (Colorado State Univ.)

    2011-01-01T23:59:59.000Z

    Control of magnetization relaxation in magnetic insulators via interfacial spin scattering is demonstrated. The experiments use nanometer-thick yttrium iron garnet (YIG)/Pt layered structures, with the Pt layer biased by an electric voltage. The bias voltage produces a spin current across the Pt thickness. As this current scatters off the YIG surface, it exerts a torque on the YIG surface spins. This torque can reduce or enhance the damping and thereby decrease or increase the ferromagnetic resonance linewidth of the YIG film, depending on the field/current configuration.

  12. Dynamic interplay between spin-crossover and host-guest function in a nanoporous metal-organic framework material.

    SciTech Connect (OSTI)

    Southon, P. D.; Liu, L.; Fellows, E. A.; Price, D. J.; Halder, G. J.; Chapman, K. W.; Moubaraki, B.; Murray, K. S.; Letard, J.F.; Kepert, C. J.; Univ. Sydney; Monash Univ.; Universite Bordeaux

    2009-01-01T23:59:59.000Z

    The nanoporous metal-organic framework [Fe(pz)Ni(CN){sub 4}], 1 (where pz is pyrazine), exhibits hysteretic spin-crossover at ambient conditions and is robust to the adsorption and desorption of a wide range of small molecular guests, both gases (N{sub 2}, O{sub 2}, CO{sub 2}) and vapors (methanol, ethanol, acetone, acetonitrile, and toluene). Through the comprehensive analysis of structure, host-guest properties, and spin-crossover behaviors, it is found that this pillared Hofmann system uniquely displays both guest-exchange-induced changes to spin-crossover and spin-crossover-induced changes to host-guest properties, with direct dynamic interplay between these two phenomena. Guest desorption and adsorption cause pronounced changes to the spin-crossover behavior according to a systematic trend in which larger guests stabilize the high-spin state and therefore depress the spin-crossover temperature of the host lattice. When stabilizing the alternate spin state of the host at any given temperature, these processes directly stimulate the spin-crossover process, providing a chemisensing function. Exploitation of the bistability of the host allows the modification of adsorption properties at a fixed temperature through control of the host spin state, with each state shown to display differing chemical affinities to guest sorption. Guest desorption then adsorption, and vice versa, can be used to switch between spin states in the bistable temperature region, adding a guest-dependent memory effect to this system.

  13. RHIC spin flipper commissioning results

    SciTech Connect (OSTI)

    Bai M.; Roser, T.; Dawson, C.; Kewisch, J.; Makdisi, Y.; Oddo, P.; Pai, C.; Pile, P.

    2012-05-20T23:59:59.000Z

    The five AC dipole RHIC spin flipper design in the RHIC Blue ring was first tested during the RHIC 2012 polarized proton operation. The advantage of this design is to eliminate the vertical coherent betatron oscillations outside the spin flipper. The closure of each ac dipole vertical bump was measured with orbital response as well as spin. The effect of the rotating field on the spin motion by the spin flipper was also confirmed by measuring the suppressed resonance at Q{sub s} = 1 - Q{sub osc}.

  14. Magnetic susceptibility and magnetization properties of asymmetric nuclear matter under a strong magnetic field

    E-Print Network [OSTI]

    A. Rabhi; M. A. Pérez-García; C. Providência; I. Vidaña

    2014-10-10T23:59:59.000Z

    We study the effect of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields $B \\sim 10^{16} - 10^{17}$ G have already noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same order or even larger for small proton fractions and subsaturation densities for $B > 10^{16}$ G. We expect that neutron superfluidity in the crust will be affected by the presence of magnetic fields.

  15. Magnetic structure of the low-dimensional magnet NaCu{sub 2}O{sub 2}: {sup 63,65}Cu and {sup 23}Na NMR studies

    SciTech Connect (OSTI)

    Sadykov, A. F., E-mail: sadykov@imp.uran.ru; Gerashchenko, A. P.; Piskunov, Yu. V.; Ogloblichev, V. V.; Smol’nikov, A. G.; Verkhovskii, S. V.; Buzlukov, A. L.; Arapova, I. Yu. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation); Furukawa, Y. [Iowa State University, Ames Laboratory (United States); Yakubovskii, A. Yu. [National Research Centre Kurchatov Institute (Russian Federation); Bush, A. A. [Moscow State Technical University of Radio Engineering, Electronics, and Automation (Russian Federation)

    2014-11-15T23:59:59.000Z

    The magnetic structure of a quasi-one-dimensional frustrated NaCu{sub 2}O{sub 2} magnet single crystal is studied by NMR. The spatial orientation of the planar spin spirals in the copper-oxygen Cu{sup 2+}-O chains is determined, and its evolution as a function of the applied magnetic field direction is analyzed.

  16. Quark spin-orbit correlations

    E-Print Network [OSTI]

    Cédric Lorcé

    2014-09-16T23:59:59.000Z

    The proton spin puzzle issue focused the attention on the parton spin and orbital angular momentum contributions to the proton spin. However, a complete characterization of the proton spin structure requires also the knowledge of the parton spin-orbit correlation. We showed that this quantity can be expressed in terms of moments of measurable parton distributions. Using the available phenomenological information about the valence quarks, we concluded that this correlation is negative, meaning that the valence quark spin and kinetic orbital angular momentum are, in average, opposite. The quark spin-orbit correlation can also be expressed more intuitively in terms of relativistic phase-space distributions, which can be seen as the mother distributions of the standard generalized and transverse-momentum dependent parton distributions. We present here for the first time some examples of the general multipole decomposition of these phase-space distributions.

  17. Spin and Madelung fluid

    E-Print Network [OSTI]

    G. Salesi

    2009-06-23T23:59:59.000Z

    Starting from the Pauli current we obtain the decomposition of the non-relativistic local velocity in two parts: one parallel and the other orthogonal to the momentum. The former is recognized to be the ``classical'' part, that is the velocity of the center-of-mass, and the latter the ``quantum'' one, that is the velocity of the motion in the center-of-mass frame (namely, the internal ``spin motion'' or {\\em Zitterbewegung}). Inserting the complete expression of the velocity into the kinetic energy term of the classical non-relativistic (i.e., Newtonian) Lagrangian, we straightforwardly derive the so-called ``quantum potential'' associated to the Madelung fluid. In such a way, the quantum mechanical behaviour of particles appears to be strictly correlated to the existence of spin and Zitterbewegung.

  18. Nuclear Magnetism and Electronic Order in 13 C Nanotubes

    E-Print Network [OSTI]

    Braunecker, Bernd

    Nuclear Magnetism and Electronic Order in 13 C Nanotubes Bernd Braunecker,1 Pascal Simon,1 on nuclear magnetism in one dimension. If the electrons are in the metallic, Luttinger liquid regime, we show that even a very weak hyperfine coupling to the 13C nuclear spins has a striking effect: The system

  19. Investigations of Magnetic Overlayers at the Advanced Photon Source

    SciTech Connect (OSTI)

    Tobin, J G; Yu, S; Butterfield, M T

    2009-06-26T23:59:59.000Z

    Magnetic overlayers of Fe and Co have been investigated with X-ray Magnetic Circular Dichroism in X-ray Absorption Spectroscopy (XMCD-ABS) and Photoelectron Spectroscopy (PES), including Spin-Resolved Photoelectron Spectroscopy (SRPES), at Beamline 4 at the Advanced Photon Source (APS). Particular emphasis was placed upon the interrogation of the 2p levels of the Fe.

  20. Topology-induced phase transitions in quantum spin Hall lattices

    SciTech Connect (OSTI)

    Bercioux, D.; Goldman, N.; Urban, D. F. [Freiburg Institute for Advanced Studies, Albert-Ludwigs-Universitaet, D-79104 Freiburg, Germany and Physikalisches Institut, Albert-Ludwigs-Universitaet, D-79104 Freiburg (Germany); Center for Nonlinear Phenomena and Complex Systems, UniversitAlbert-Ludwigs-Universitaet Libre de Bruxelles (U.L.B.), Code Postal 231, Campus Plaine, B-1050 Brussels (Belgium); Physikalisches Institut, Albert-Ludwigs-Universitaet, D-79104 Freiburg (Germany)

    2011-02-15T23:59:59.000Z

    Physical phenomena driven by topological properties, such as the quantum Hall effect, have the appealing feature that they are robust with respect to external perturbations. Lately, a new class of materials has emerged that manifests topological properties at room temperature and without the need of external magnetic fields. These topological insulators are band insulators with large spin-orbit interactions and exhibit the quantum spin-Hall (QSH) effect. Here we investigate the transition between QSH and normal insulating phases under topological deformations of a two-dimensional lattice. We demonstrate that the QSH phase present in the honeycomb lattice loses its robustness as the occupancy of extra lattice sites is allowed. Furthermore, we propose a method for verifying our predictions with fermionic cold atoms in optical lattices. In this context, the spin-orbit interaction is engineered via an appropriate synthetic gauge field.

  1. Linear optics, Raman scattering, and spin noise spectroscopy

    E-Print Network [OSTI]

    Glazov, M M

    2015-01-01T23:59:59.000Z

    Spin noise spectroscopy (SNS) is a new method for studying magnetic resonance and spin dynamics based on measuring the Faraday rotation noise. In strong contrast with methods of nonlinear optics, the spectroscopy of spin noise is considered to be essentially nonperturbative. Presently, however, it became clear that the SNS, as an optical technique, demonstrates properties lying far beyond the bounds of conventional linear optics. Specifically, the SNS shows dependence of the signal on the light power density, makes it possible to penetrate inside an inhomogeneously broadened absorption band and to determine its homogeneous width, allows one to realize an effective pump-probe spectroscopy without any optical nonlinearity, etc. This may seem especially puzzling when taken into account that SNS can be considered just as a version of Raman spectroscopy, which is known to be deprived of such abilities. In this paper, we clarify this apparent inconsistency.

  2. A spin light emitting diode incorporating ability of electrical helicity switching

    SciTech Connect (OSTI)

    Nishizawa, N., E-mail: nishizawa@isl.titech.ac.jp; Nishibayashi, K.; Munekata, H. [Imaging Science and Engineering Laboratory, Tokyo Institute of Technology, 4259-J3-15 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)

    2014-03-17T23:59:59.000Z

    Fabrication and optical characteristics of a spin light-emitting-diode (spin-LED) having dual spin-injection electrodes with anti-parallel magnetization configuration are reported. Alternating a current between the two electrodes using a computer-driven current source has led us to the observation of helicity switching of circular polarization at the frequency of 1 kHz. Neither external magnetic fields nor optical delay modulators were used. Sending dc-currents to both electrodes with appropriate ratio has resulted in continuous variation of circular polarization between the two opposite helicity, including the null polarization. These results suggest that the tested spin-LED has the feasibility of a monolithic light source whose circular polarization can be switched or continuously tuned all electrically.

  3. Spin switches for compact implementation of neuron and synapse

    SciTech Connect (OSTI)

    Quang Diep, Vinh, E-mail: vdiep@purdue.edu; Sutton, Brian; Datta, Supriyo [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Behin-Aein, Behtash [GLOBALFOUNDRIES, Inc., Sunnyvale, California 94085 (United States)

    2014-06-02T23:59:59.000Z

    Nanomagnets driven by spin currents provide a natural implementation for a neuron and a synapse: currents allow convenient summation of multiple inputs, while the magnet provides the threshold function. The objective of this paper is to explore the possibility of a hardware neural network implementation using a spin switch (SS) as its basic building block. SS is a recently proposed device based on established technology with a transistor-like gain and input-output isolation. This allows neural networks to be constructed with purely passive interconnections without intervening clocks or amplifiers. The weights for the neural network are conveniently adjusted through analog voltages that can be stored in a non-volatile manner in an underlying CMOS layer using a floating gate low dropout voltage regulator. The operation of a multi-layer SS neural network designed for character recognition is demonstrated using a standard simulation model based on coupled Landau-Lifshitz-Gilbert equations, one for each magnet in the network.

  4. Spin Coherence at the Nanoscale: Polymer Surfaces and Interfaces

    SciTech Connect (OSTI)

    Epstein, Arthur J. [Professor

    2013-09-10T23:59:59.000Z

    Breakthrough results were achieved during the reporting period in the areas of organic spintronics. (A) For the first time the giant magnetic resistance (GMR) was observed in spin valve with an organic spacer. Thus we demonstrated the ability of organic semiconductors to transport spin in GMR devices using rubrene as a prototype for organic semiconductors. (B) We discovered the electrical bistability and spin valve effect in a ferromagnet /organic semiconductor/ ferromagnet heterojunction. The mechanism of switching between conducting phases and its potential applications were suggested. (C) The ability of V(TCNE)x to inject spin into organic semiconductors such as rubrene was demonstrated for the first time. The mechanisms of spin injection and transport from and into organic magnets as well through organic semiconductors were elucidated. (D) In collaboration with the group of OSU Prof. Johnston-Halperin we reported the successful extraction of spin polarized current from a thin film of the organic-based room temperature ferrimagnetic semiconductor V[TCNE]x and its subsequent injection into a GaAs/AlGaAs light-emitting diode (LED). Thus all basic steps for fabrication of room temperature, light weight, flexible all organic spintronic devices were successfully performed. (E) A new synthesis/processing route for preparation of V(TCNE)x enabling control of interface and film thicknesses at the nanoscale was developed at OSU. Preliminary results show these films are higher quality and what is extremely important they are substantially more air stable than earlier prepared V(TCNE)x. In sum the breakthrough results we achieved in the past two years form the basis of a promising new technology, Multifunctional Flexible Organic-based Spintronics (MFOBS). MFOBS technology enables us fabrication of full function flexible spintronic devices that operate at room temperature.

  5. Magnetic properties and magnetocaloric effect in the RCu{sub 2}Si{sub 2} and RCu{sub 2}Ge{sub 2} (R?=?Ho, Er) compounds

    SciTech Connect (OSTI)

    Mo, Zhao-Jun [School of Material Science and Engineering, Hebei University of Technology, Tianjin (China); Key laboratory of cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing (China); Shen, Jun, E-mail: jshen@mail.ipc.ac.cn, E-mail: tangcc@hebut.edu.cn; Wu, Jian-Feng [Key laboratory of cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing (China); Yan, Li-Qin; Wang, Li-Chen; Sun, Ji-rong; Shen, Bao-Gen [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter, Physics and Institute of Physics, Chinese Academy of Sciences, Beijing (China); Gao, Xin-Qiang; Tang, Cheng-Chun, E-mail: jshen@mail.ipc.ac.cn, E-mail: tangcc@hebut.edu.cn [School of Material Science and Engineering, Hebei University of Technology, Tianjin (China)

    2014-02-21T23:59:59.000Z

    The magnetic properties and magnetocaloric effect (MCE) in RCu{sub 2}Si{sub 2} and RCu{sub 2}Ge{sub 2} (R?=?Ho, Er) compounds have been investigated. All these compounds possess an antiferromagnetic (AFM)-paramagnetic (PM) transition around their respective Neel temperatures. The RCu{sub 2}Si{sub 2} compounds undergo spin-glassy behavior above Neel temperature. Furthermore, a field-induced metamagnetic transition from AFM to ferromagnetic (FM) states is observed in these compounds. The calculated magnetic entropy changes show that all RCu{sub 2}Si{sub 2} and RCu{sub 2}Ge{sub 2} (R?=?Ho, Er) compounds, especially, ErCu{sub 2}Si{sub 2} exhibits large MCEs with no thermal hysteresis and magnetic hysteresis loss. The value of ??S{sub M}{sup max} reaches 22.8?J/Kg K for magnetic field changes from 0 to 5?T. In particular, for field changes of 1 and 2?T, the giant reversible magnetic entropy changes ??S{sub M}{sup max} are 8.3 and 15.8?J/kg K at 2.5?K, which is lower than the boiling point of helium. The low-field giant magnetic entropy change, together with ignorable thermal hysteresis and field hysteresis loss of ErCu{sub 2}Si{sub 2} compound is expected to have effective applications in low temperature magnetic refrigeration.

  6. Magnetic System for the CLAS12 Proposal

    SciTech Connect (OSTI)

    Statera, Marco [INFN, Ferrara (Italy); Contalbrigo, Marco M. [INFN, Ferrara (Italy); Pappalardo, Luciano Libero [INFN, Ferrara (Italy); Barion, Luca [INFN, Ferrara (Italy); Bertelli, S. [INFN, Ferrara (Italy); Ciullo, Giuseppe [INFN, Ferrara (Italy); Lenisa, Paolo [INFN, Ferrara (Italy)

    2013-06-01T23:59:59.000Z

    The conceptual design of a magnetic system for an experiment to measure the transverse spin effects in semi-inclusive Deep Inelastic Scattering (SIDIS) at 11 GeV with a transversely polarized target using the CLAS12 detector at Jefferson Lab is presented. A proposal has been submitted to study spin azimuthal asymmetries in SIDIS using an 11-GeV polarized electron beam from the upgraded CEBAF facility and the CLAS12 detector equipped with a transversely polarized target. The main focus of the experiment will be the measurement of transverse target single and double spin asymmetries in the reaction ep{up_arrow} -> ehX, where e is an electron, p{up_arrow} is transversely polarized proton, h is a meson (e.g., a pion or a kaon) and X is the undetected final state. The details of the conceptual design of the shielding magnetic system and transverse dipole are reported.

  7. Electronic waiting-time distribution of a quantum-dot spin valve

    E-Print Network [OSTI]

    Björn Sothmann

    2014-10-27T23:59:59.000Z

    We discuss the electronic waiting-time distribution of a quantum-dot spin valve, i.e. a single-level quantum dot coupled to two ferromagnetic electrodes with magnetizations that can point in arbitrary directions. We demonstrate that the rich transport physics of this setup such as dynamical channel blockade and spin precession in an interaction-driven exchange field shows up in the waiting-time distribution and analyze the conditions necessary to observe the various effects.

  8. Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves

    SciTech Connect (OSTI)

    Thurber, Kent R., E-mail: thurberk@niddk.nih.gov; Tycko, Robert [Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)] [Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)

    2014-05-14T23:59:59.000Z

    We report solid state {sup 13}C and {sup 1}H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, {sup 1}H and cross-polarized {sup 13}C NMR signals from {sup 15}N,{sup 13}C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T{sub 1e} is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.

  9. Nuclear magnetic ordering in Ca(OH)2. III. Experimental determination of the critical temperature

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    1479 Nuclear magnetic ordering in Ca(OH)2. III. Experimental determination of the critical(OH)2 is presented. The ordered phase is reached via dynamic nuclear polarization followed to the effective magnetic field are used to determine the magnetic phase of the nuclear spin system. From

  10. A Miniature Continuous Adiabatic Demagnetization Refrigerator with compact shielded superconducting magnets.

    E-Print Network [OSTI]

    Timbie, Peter

    insulated from the bath. The refrigeration cycle exploits the interaction between the atomic magnetic a magnetic field is applied to a param- agnetic refrigerant, its magnetic spins are aligned and orderedA Miniature Continuous Adiabatic Demagnetization Refrigerator with compact shielded superconducting

  11. Spin effect on parametric decay of oblique Langmuir wave in degenerate magneto-plasmas

    SciTech Connect (OSTI)

    Shahid, M. [Salam Chair in Physics, Government College University, Lahore-54000 (Pakistan) [Salam Chair in Physics, Government College University, Lahore-54000 (Pakistan); Department of Physics, Government College University, Lahore-54000 (Pakistan); Murtaza, G. [Salam Chair in Physics, Government College University, Lahore-54000 (Pakistan)] [Salam Chair in Physics, Government College University, Lahore-54000 (Pakistan)

    2013-08-15T23:59:59.000Z

    The electron spin ?1/2 effects on the parametric decay instability of oblique Langmuir wave into low-frequency electromagnetic shear Alfven wave and Left-Handed Circularly Polarized wave (LHCP) has been investigated in detail, in an electron-ion quantum plasma immersed in the uniform external magnetic field. Incorporating the quantum effects due to electron spin, Fermi pressure and Bohm potential term, the quantum magneto-hydrodynamic (QMHD) model has been used to investigate the linear and nonlinear response of the plasma species for three-wave coupling interaction in a quantum magneto-plasmas. Nonlinear dispersion relations and growth rate of the problem have been derived analytically. It has been shown that the spin of electrons has considerable effect on the growth rate of parametric instability problem even when the external magnetic field B{sub 0} is below the quantum critical magnetic field strength B{sub Q}=4.4138×10{sup 13}G.

  12. High-spin rotational structures in {sup 76}Kr

    SciTech Connect (OSTI)

    Valiente-Dobon, J.J.; Svensson, C.E.; Finlay, P.; Grinyer, G.F.; Hyland, B.; Phillips, A.A.; Schumaker, M.A. [Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); O'Leary, C.D.; Jenkins, D.; Johnston-Theasby, F.; Joshi, P.; Kelsall, N.S.; Wadsworth, R. [Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); Ragnarsson, I. [Department of Physics, Lund Institute of Technology, P.O. Box 118, S-221 00 Lund (Sweden); Andreoiu, C. [Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 3BX (United Kingdom); Appelbe, D.E. [CLRC Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom); Austin, R.A.E.; Cameron, J.A.; Waddington, J.C. [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4K1 (Canada); Ball, G.C. [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3 (Canada)] [and others

    2005-03-01T23:59:59.000Z

    High-spin states in {sup 36}{sub 76}Kr{sub 40} have been populated in the {sup 40}Ca({sup 40}Ca,4p){sup 76}Kr fusion-evaporation reaction at a beam energy of 165 MeV and studied using the Gammasphere and Microball multidetector arrays. The ground-state band and two signature-split negative parity bands of {sup 76}Kr have been extended to {approx}30({Dirac_h}/2{pi}). Lifetime measurements using the Doppler-shift attenuation method show that the transition quadrupole moment of these three bands decrease as they approach their maximum-spin states. Two signatures of a new rotational structure with remarkably rigid rotational behavior have been identified. The high-spin properties of these rotational bands are analyzed within the framework of configuration-dependent cranked Nilsson-Strutinsky calculations.

  13. Feedback control of spin systems

    E-Print Network [OSTI]

    Claudio Altafini

    2006-01-03T23:59:59.000Z

    The feedback stabilization problem for ensembles of coupled spin 1/2 systems is discussed from a control theoretic perspective. The noninvasive nature of the bulk measurement allows for a fully unitary and deterministic closed loop. The Lyapunov-based feedback design presented does not require spins that are selectively addressable. With this method, it is possible to obtain control inputs also for difficult tasks, like suppressing undesired couplings in identical spin systems.

  14. Asymptotics of Relativistic Spin Networks

    E-Print Network [OSTI]

    John W Barrett; Christopher M Steele

    2003-01-31T23:59:59.000Z

    The stationary phase technique is used to calculate asymptotic formulae for SO(4) Relativistic Spin Networks. For the tetrahedral spin network this gives the square of the Ponzano-Regge asymptotic formula for the SU(2) 6j symbol. For the 4-simplex (10j-symbol) the asymptotic formula is compared with numerical calculations of the Spin Network evaluation. Finally we discuss the asymptotics of the SO(3,1) 10j-symbol.

  15. Heterostructure unipolar spin transistors M. E. Flatta

    E-Print Network [OSTI]

    Flatte, Michael E.

    carriers on one side of the device are spin-down spin-up electrons and on the other side of the device semiconductor electronics and spin-based unipolar electronics by considering unipolar spin transistors electrons to the collector limits the performance of "homojunction" unipolar spin transistors, in which

  16. Neutrino spin oscillations in matter under the influence of gravitational and electromagnetic fields

    SciTech Connect (OSTI)

    Dvornikov, Maxim, E-mail: maxim.dvornikov@usp.br [Institute of Physics, University of São Paulo, CP 66318, CEP 05315-970 São Paulo, SP (Brazil)

    2013-06-01T23:59:59.000Z

    We derive the new quasi-classical equation for the description of the spin evolution of a neutrino propagating in a curved space-time and interacting with a background matter and an external electromagnetic field. This equation is used to analyze neutrino spin oscillations in these external backgrounds. We obtain the effective Hamiltonian and the transition probability for oscillations of neutrinos when they move in the vicinity of a rotating black hole, surrounded by an accretion disk, and interact with an external magnetic field. The appearance of new resonances in neutrino spin oscillations in this system is considered. The approximate treatment of spin oscillations of radially propagating ultra high energy neutrinos is developed. We also discuss the applications of our results to the description of neutrino spin oscillations in realistic astrophysical media.

  17. Room-temperature spin-polarized organic light-emitting diodes with a single ferromagnetic electrode

    SciTech Connect (OSTI)

    Ding, Baofu, E-mail: b.ding@ecu.edu.au; Alameh, Kamal, E-mail: k.alameh@ecu.edu.au [Electron Science Research Institute, Edith Cowan University, 270 Joondalup Drive, Joondalup WA 6027 Australia (Australia); Song, Qunliang [Institute for Clean Energy and Advanced Materials, Southwest University, Chongqing 400715 (China)

    2014-05-19T23:59:59.000Z

    In this paper, we demonstrate the concept of a room-temperature spin-polarized organic light-emitting diode (Spin-OLED) structure based on (i) the deposition of an ultra-thin p-type organic buffer layer on the surface of the ferromagnetic electrode of the Spin-OLED and (ii) the use of oxygen plasma treatment to modify the surface of that electrode. Experimental results demonstrate that the brightness of the developed Spin-OLED can be increased by 110% and that a magneto-electroluminescence of 12% can be attained for a 150?mT in-plane magnetic field, at room temperature. This is attributed to enhanced hole and room-temperature spin-polarized injection from the ferromagnetic electrode, respectively.

  18. Phase-controllable spin wave generation in iron garnet by linearly polarized light pulses

    SciTech Connect (OSTI)

    Yoshimine, Isao; Iida, Ryugo; Shimura, Tsutomu [Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505 (Japan); Satoh, Takuya, E-mail: satoh@phys.kyushu-u.ac.jp [Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505 (Japan); PRESTO, Japan Science and Technology Agency, Tokyo 102-0076 (Japan); Department of Physics, Kyushu University, Fukuoka 812-8581 (Japan); Stupakiewicz, Andrzej; Maziewski, Andrzej [Laboratory of Magnetism, Faculty of Physics, University of Bialystok, Bialystok 15-424 (Poland)

    2014-07-28T23:59:59.000Z

    A phase-controlled spin wave was non-thermally generated in bismuth-doped rare-earth iron garnet by linearly polarized light pulses. We controlled the initial phase of the spin wave continuously within a range of 180° by changing the polarization azimuth of the excitation light. The azimuth dependences of the initial phase and amplitude of the spin wave were attributed to a combination of the inverse Cotton-Mouton effect and photoinduced magnetic anisotropy. Temporally and spatially resolved spin wave propagation was observed with a CCD camera, and the waveform was in good agreement with calculations. A nonlinear effect of the spin excitation was observed for excitation fluences higher than 100 mJ/cm{sup 2}.

  19. Spin-polarized nitroxide radicals in organic glasses.

    SciTech Connect (OSTI)

    Tarasov, V. F.; Shkrob, I. A.; Trifunac, A. D.; Chemistry

    2002-01-01T23:59:59.000Z

    Nonequilibrium spin polarization formed in a stable nitroxide radical, 2,2,6,6-tetramethyl-1-piperidinyloxy (Tempo) due to the occurrence of Chemically Induced Dynamic Electron Polarization (CIDEP) in photoexcited molecular complexes of this radical with 1,4-benzoquinone, 1,4-naphthaquinone, 9,10-anthraquinone, and their derivatives is observed. These complexes occur spontaneously in low-temperature organic glasses (20-70 K) upon freezing the concentrated liquid solutions. The emissive net polarization in the nitroxide radical is observed 0.1-10 {mu}s after the photoexcitation of the p-quinone moiety. No degradation of the polarized magnetic resonance signal from Tempo after >104 excitation cycles was observed. This spin polarization is shown to be mainly due to a polarization transfer from the lowest triplet state of the p-quinone. This transfer is driven by the electron spin exchange interaction between the nitroxide radical and the triplet p-quinone; it occurs simultaneously with a spin-selective electronic relaxation of the photoexcited complex. The resulting mechanism combines the features of the electron spin polarization transfer (ESPT) and radical-triplet pair mechanisms (RTPM) in liquid. A theoretical model of such a mechanism is suggested.

  20. Quantum Simulation of Spin Chains Coupled to Bosonic Modes with Superconducting Circuits

    E-Print Network [OSTI]

    U. Las Heras; L. García-Álvarez; A. Mezzacapo; E. Solano; L. Lamata

    2015-07-13T23:59:59.000Z

    We propose the implementation of a digital quantum simulation of spin chains coupled to bosonic field modes in superconducting circuits. Gates with high fidelities allows one to simulate a variety of Ising magnetic pairing interactions with transverse field, Tavis-Cummings interaction between spins and a bosonic mode, and a spin model with three-body terms. We analyze the feasibility of the implementation in realistic circuit quantum electrodynamics setups, where the interactions are either realized via capacitive couplings or mediated by microwave resonators.

  1. Quantum Simulation of Spin Chains Coupled to Bosonic Modes with Superconducting Circuits

    E-Print Network [OSTI]

    U. Las Heras; L. García-Álvarez; A. Mezzacapo; E. Solano; L. Lamata

    2015-07-09T23:59:59.000Z

    We propose the implementation of a digital quantum simulation of spin chains coupled to bosonic field modes in superconducting circuits. Gates with high fidelities allows one to simulate a variety of Ising magnetic pairing interactions with transverse field, Tavis-Cummings interaction between spins and a bosonic mode, and a spin model with three-body terms. We analyze the feasibility of the implementation in realistic circuit quantum electrodynamics setups, where the interactions are either realized via capacitive couplings or mediated by microwave resonators.

  2. The spin exchange interaction effect on Tc equation of anisotropic impure superconductors

    E-Print Network [OSTI]

    P. Udomsamuthirun; R. Supadanaison

    2008-04-10T23:59:59.000Z

    We study the influence of spin exchange interaction of impurity scattering on critical temperature of anisotropic impure superconductors. The model of random nonmagnetic and magnetic impurity are revised to cover the effect of spin exchange interaction . The sign of magnitude of the second-order Born scattering have been changed after consideration the spin exchange interaction effect that also effect to form of Tc equation. We can get the general Tc equation that can be described anisotropic impure superconductors well and cover all model done before.

  3. Neutron Scattering Study on spin dynamics in superconducting (TlRb)2Fe4Se5

    SciTech Connect (OSTI)

    Chi, Songxue [ORNL; Ye, Feng [ORNL; Bao, Wei [Renmin University of China; Fang, Dr. Minghu [Zhejiang University; Wang, H.D. [Zhejiang University; Dong, C.H. [Zhejiang University; Savici, Andrei T [ORNL; Granroth, Garrett E [ORNL; Stone, Matthew B [ORNL; Fishman, Randy Scott [ORNL

    2013-01-01T23:59:59.000Z

    Spin dynamics in superconducting (Tl,Rb)2Fe4Se5 was investigated using the inelastic neutron scattering technique. Spin wave branches that span an energy range from 6.5 to 209 meV are success- fully described by a Heisenberg model whose dominant interactions include only the in-plane nearest (J1 and J0 1) and next nearest neighbor (J2 and J0 2) exchange terms within and between the tetramer spin blocks, respectively. These exchange constants, experimentally determined in this work, would crucially constrain the diverse theoretical viewpoints on magnetism and superconductivity in the Fe-based materials.

  4. Spin-dependent recombination at arsenic donors in ion-implanted silicon

    SciTech Connect (OSTI)

    Franke, David P., E-mail: david.franke@wsi.tum.de; Brandt, Martin S. [Walter Schottky Institut and Physik-Department, Technische Universität München, Am Coulombwall 4, 85748 Garching (Germany); Otsuka, Manabu; Matsuoka, Takashi; Itoh, Kohei M. [School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Vlasenko, Leonid S.; Vlasenko, Marina P. [A. F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation)

    2014-09-15T23:59:59.000Z

    Spin-dependent transport processes in thin near-surface doping regions created by low energy ion implantation of arsenic in silicon are detected by two methods, spin-dependent recombination using microwave photoconductivity and electrically detected magnetic resonance monitoring the direct current through the sample. The high sensitivity of these techniques allows the observation of the magnetic resonance, in particular, of As in weak magnetic fields and at low resonance frequencies (40–1200 MHz), where high-field-forbidden transitions between the magnetic sublevels can be observed due to the mixing of electron and nuclear spin states. Several implantation-induced defects are present in the samples studied and act as spin readout partner. We explicitly demonstrate this by electrically detected electron double resonance experiments and identify a pair recombination of close pairs formed by As donors and oxygen-vacancy centers in an excited triplet state (SL1) as the dominant spin-dependent process in As-implanted Czochralski-grown Si.

  5. Determination of the Pt spin diffusion length by spin-pumping and spin Hall effect

    SciTech Connect (OSTI)

    Zhang, Wei; Pearson, John E.; Hoffmann, Axel [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Vlaminck, Vincent [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States) [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Colegio de Ciencias e Ingenería, Universidad San Fransciso de Quito, Quito (Ecuador); Divan, Ralu [Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States)] [Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States); Bader, Samuel D. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States) [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States)

    2013-12-09T23:59:59.000Z

    The spin diffusion length of Pt at room temperature and at 8 K is experimentally determined via spin pumping and spin Hall effect in permalloy/Pt bilayers. Voltages generated during excitation of ferromagnetic resonance from the inverse spin Hall effect and anisotropic magnetoresistance effect were investigated with a broadband approach. Varying the Pt layer thickness gives rise to an evolution of the voltage line shape due to the superposition of the above two effects. By studying the ratio of the two voltage components with the Pt layer thickness, the spin diffusion length of Pt can be directly extracted. We obtain a spin diffusion length of ?1.2 nm at room temperature and ?1.6 nm at 8 K.

  6. Weakly relativistic quantum kinetic theory for electrostatic wave modes in magnetized plasmas

    SciTech Connect (OSTI)

    Hussain, Azhar [Department of Physics, GC University Lahore, 54000 Lahore (Pakistan)] [Department of Physics, GC University Lahore, 54000 Lahore (Pakistan); Stefan, Martin; Brodin, Gert [Department of Physics, Umeå University, SE-901 87 Umeå (Sweden)] [Department of Physics, Umeå University, SE-901 87 Umeå (Sweden)

    2014-03-15T23:59:59.000Z

    We have derived the electrostatic dispersion relation in a magnetized plasma using a recently developed quantum kinetic model based on the Dirac equation. The model contains weakly relativistic spin effects such as Thomas precession, the polarization currents associated with the spin and the spin-orbit coupling. It turns out that for strictly electrostatic perturbations the non-relativistic spin effects vanish, and the modification of the classical dispersion relation is solely associated with the relativistic terms. Several new wave modes appear due the electron spin effects, and an example for astrophysical plasmas are given.

  7. Nuclear Spin Relaxation Induced by a Mechanical Resonator C. L. Degen,1,* M. Poggio,1,2

    E-Print Network [OSTI]

    Leonardo, Degiorgi

    , equivalent to about 108 net magnetic moments [2]. Stronger couplings enabling higher spin sensitivity have with magnetic noise generated by the thermally vibrating cantilever, but similar effects can be expected in any real-world detector, as, for example, in an inductively coupled rf circuit. The interaction between

  8. Magnetic and transport properties of heat-treated polyparaphenylene-based carbons

    SciTech Connect (OSTI)

    Matthews, M.J.; Kobayashi, N.; Dresselhaus, M.S.; Endo, M.; Enoki, T.; Karaki, T.

    1998-07-01T23:59:59.000Z

    Electron spin resonance (ESR), magnetic susceptibility, and transport measurements were recently performed on a set of heat-treated polyparaphenylene (PPP)-based carbon samples, which are of significant interest as novel carbon-based anode electrodes in Li-ion batteries. Attention is focused on the evolution of the carbonaceous structures formed at low heat-treatment temperatures (T{sub HT}) in the regime of 600 C {le} T{sub HT} {le} 800 C, where percolative transport behavior is observed. At the percolation threshold, T{sub HT}{sup c} {approx} 700 C the coexistence of two spin centers with peak-to-peak Lorentzian linewidths of {Delta}H{sub pp}(300K) = 0.5 and 5.0 G is observed. The relatively high ratio of hydrogen carbon (H/C) near T{sub HT}{sup c} is believed to influence the ESR results through an unresolved hyperfine interaction. Curie-Weiss temperatures are found from measurements of [I{sub pp}({Delta}H{sub pp}){sup 2}]{sup {minus}1}, where I{sub pp} is the peak-to-peak lineheight, yielding results that are in agreement with static susceptibility, {chi}(T), measurements. At low T{sub HT}, PPP-based materials exhibit a large amount of disorder and this is evidenced by the high density of localized spins, N{sub C}, which is obtained from a Curie-Weiss fit to {chi}(T), assuming a spin quantum number of S = {1/2}. A model explaining the microstructure and high electrochemical doping capacity of PPP samples heat-treated to 700 C can be related to Li-ion battery performance.

  9. Spin-rotation coupling in compound spin objects

    E-Print Network [OSTI]

    G. Lambiase; G. Papini

    2013-01-31T23:59:59.000Z

    We generalize spin-rotation coupling to compound spin systems. In the case of muons bound to nuclei in a storage ring the decay process acquires a modulation. Typical frequencies for $Z/A\\sim 1/2$ are $\\sim 3\\times 10^6$Hz, a factor 10 higher than the modulation observed in $g-2$ experiments.

  10. Industries and Spin-offs 485 and Spin-offs

    E-Print Network [OSTI]

    -based Rockwell allocated work to rivals in other parts of the country. Grumman of Long Island, New York, whichIndustries and Spin-offs 485 Industries and Spin-offs #12;In the late 1960s, many of America Richard Nixon's approval of the Space Shuttle Program came along just in time for an industry whose future

  11. Combined experimental and theoretical study of the low temperature dielectric and magnetic properties of trivalent Eu ion doped SrTiO{sub 3} ceramics

    SciTech Connect (OSTI)

    Yu Jiangzhou; Fang Liang; Cai Tianyi; Ju Sheng; Dong Wen; Zheng Fengang; Shen Mingrong [Jiangsu Key Laboratory of Thin Films and Department of Physics, Soochow University, Suzhou, 215006 (China)

    2012-03-15T23:59:59.000Z

    Single-phase Sr{sub 1-3x/2}Eu{sub x}TiO{sub 3} (SETO{sub x}) (x = 0-0.075) ceramics were prepared to study the effects of Eu substitution on their crystal structure, low temperature dielectric, and magnetic behaviors. Rietveld refinement of X-ray diffraction data yields direct evidence that the Eu ion substitutes Sr site at the perovskite. The measured dielectric properties can be well explained by the mean-field model. It has been found that the anomaly dielectric enhancement behavior exists in the SETO{sub x=0.005} sample, while more stable quantum paraelectric states are obtained in other doped samples. On the other hand, all the Eu doped samples exhibit doping concentration dependence of paramagnetism. Developing the linear response model, we conclude that a molecular field is acting on Eu ions possibly via the spin polarized Eu-O-Ti hybridization.

  12. Critical behavior and universality in Levy spin glasses

    E-Print Network [OSTI]

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

    2011-01-01T23:59:59.000Z

    (Grant No. PP002-114713). The authors acknowledge ETH Zurich for CPU time on the Brutus cluster. 1D. Daboul, I. Chang, and A. Aharony, Eur. Phys. J. B 41, 231 (2004). 2K. Binder and A. P. Young, Rev. Mod. Phys. 58, 801 (1986). 3A. T. Ogielski and I.... Morgenstern, Phys. Rev. Lett. 54, 928 (1985). 4A. T. Ogielski, Phys. Rev. B 32, 7384 (1985). 5W. L. McMillan, Phys. Rev. B 31, 340 (1985). 6R. R. P. Singh and S. Chakravarty, Phys. Rev. Lett. 57, 245 (1986). 7A. J. Bray and M. A. Moore, Phys. Rev. B 31...

  13. Pulsar Kicks Induced by Spin Flavor Oscillations of Neutrinos in Gravitational Fields

    E-Print Network [OSTI]

    G. Lambiase

    2005-07-15T23:59:59.000Z

    The origin of pulsar kicks is reviewed in the framework of the spin-flip conversion of neutrinos propagating in the gravitational field of a magnetized protoneutron star. We find that for a mass in rotation with angular velocity ${\\bbox \\omega}$, the spin connections entering in the Dirac equation give rise to the coupling term ${\\bbox \\omega}\\cdot {\\bf p}$, being ${\\bf p}$ the neutrino momentum. Such a coupling can be responsible of pulsar kicks owing to the neutrino emission asymmetry generated by the relative orientation of ${\\bf p}$ with respect to ${\\bbox \\omega}$. For our estimations, the large non standard neutrino magnetic momentum, $\\mu_\

  14. Unidirectional anisotropy in the spin pumping voltage in yttrium iron garnet/platinum bilayers

    SciTech Connect (OSTI)

    Vilela-Leao, L. H.; Salvador, C.; Azevedo, A.; Rezende, S. M.

    2011-09-05T23:59:59.000Z

    Detailed measurements of the dc voltage generated in a thin Pt layer deposited on films of yttrium iron garnet (YIG) have been carried out to study the spin pumping effect produced by magnetostatic (MS) modes excited by a microwave field. In relatively thick YIG films the modes are far apart so that one can identify clearly the spin pumping voltage in V{sub SP} produced by each MS mode. We have discovered that when the sputter deposition of the thin Pt layer is made on the YIG film magnetized by a static magnetic field, V{sub SP} exhibits a strong unidirectional anisotropy.

  15. Electronic and magnetic structures of the postperovskite-type Fe[subscript 2]O[subscript 3] and implications for planetary magnetic records and deep interiors

    E-Print Network [OSTI]

    Shim, Sang-Heon Dan

    Recent studies have shown that high pressure (P) induces the metallization of the Fe[superscript 2+]–O bonding, the destruction of magnetic ordering in Fe, and the high-spin (HS) to low-spin (LS) transition of Fe in silicate ...

  16. Manifold corrections on spinning compact binaries

    SciTech Connect (OSTI)

    Zhong Shuangying; Wu Xin [Nanchang University, Nanchang 330031 (China)

    2010-05-15T23:59:59.000Z

    This paper deals mainly with a discussion of three new manifold correction methods and three existing ones, which can numerically preserve or correct all integrals in the conservative post-Newtonian Hamiltonian formulation of spinning compact binaries. Two of them are listed here. One is a new momentum-position scaling scheme for complete consistency of both the total energy and the magnitude of the total angular momentum, and the other is the Nacozy's approach with least-squares correction of the four integrals including the total energy and the total angular momentum vector. The post-Newtonian contributions, the spin effects, and the classification of orbits play an important role in the effectiveness of these six manifold corrections. They are all nearly equivalent to correct the integrals at the level of the machine epsilon for the pure Kepler problem. Once the third-order post-Newtonian contributions are added to the pure orbital part, three of these corrections have only minor effects on controlling the errors of these integrals. When the spin effects are also included, the effectiveness of the Nacozy's approach becomes further weakened, and even gets useless for the chaotic case. In all cases tested, the new momentum-position scaling scheme always shows the optimal performance. It requires a little but not much expensive additional computational cost when the spin effects exist and several time-saving techniques are used. As an interesting case, the efficiency of the correction to chaotic eccentric orbits is generally better than one to quasicircular regular orbits. Besides this, the corrected fast Lyapunov indicators and Lyapunov exponents of chaotic eccentric orbits are large as compared with the uncorrected counterparts. The amplification is a true expression of the original dynamical behavior. With the aid of both the manifold correction added to a certain low-order integration algorithm as a fast and high-precision device and the fast Lyapunov indicators of two nearby trajectories, phase space scans for chaos in the spinning compact binary system are given.

  17. Simulating merging binary black holes with nearly extremal spins

    SciTech Connect (OSTI)

    Lovelace, Geoffrey [Center for Radiophysics and Space Research, Cornell University, Ithaca, New York, 14853 (United States); Scheel, Mark A.; Szilagyi, Bela [Theoretical Astrophysics 350-17, California Institute of Technology, Pasadena, California 91125 (United States)

    2011-01-15T23:59:59.000Z

    Astrophysically realistic black holes may have spins that are nearly extremal (i.e., close to 1 in dimensionless units). Numerical simulations of binary black holes are important tools both for calibrating analytical templates for gravitational-wave detection and for exploring the nonlinear dynamics of curved spacetime. However, all previous simulations of binary-black-hole inspiral, merger, and ringdown have been limited by an apparently insurmountable barrier: the merging holes' spins could not exceed 0.93, which is still a long way from the maximum possible value in terms of the physical effects of the spin. In this paper, we surpass this limit for the first time, opening the way to explore numerically the behavior of merging, nearly extremal black holes. Specifically, using an improved initial-data method suitable for binary black holes with nearly extremal spins, we simulate the inspiral (through 12.5 orbits), merger and ringdown of two equal-mass black holes with equal spins of magnitude 0.95 antialigned with the orbital angular momentum.

  18. Time-resolved observation of fast domain-walls driven by vertical spin currents in short tracks

    SciTech Connect (OSTI)

    Sampaio, Joao; Lequeux, Steven; Chanthbouala, Andre; Cros, Vincent; Grollier, Julie [Unité Mixte de Physique CNRS/Thales and Université Paris-Sud 11, 1 Ave. A. Fresnel, 91767 Palaiseau (France)] [Unité Mixte de Physique CNRS/Thales and Université Paris-Sud 11, 1 Ave. A. Fresnel, 91767 Palaiseau (France); Metaxas, Peter J. [Unité Mixte de Physique CNRS/Thales and Université Paris-Sud 11, 1 Ave. A. Fresnel, 91767 Palaiseau (France) [Unité Mixte de Physique CNRS/Thales and Université Paris-Sud 11, 1 Ave. A. Fresnel, 91767 Palaiseau (France); School of Physics, M013, University of Western Australia, 35 Stirling Highway, Crawley WA 6009 (Australia); Matsumoto, Rie; Yakushiji, Kay; Kubota, Hitoshi; Fukushima, Akio; Yuasa, Shinji [National Institute of Advanced Industrial Science and Technology (AIST) 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)] [National Institute of Advanced Industrial Science and Technology (AIST) 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Nishimura, Kazumasa; Nagamine, Yoshinori; Maehara, Hiroki; Tsunekawa, Koji [Process Development Center, Canon ANELVA Corporation, Kurigi 2-5-1, Asao, Kawasaki, Kanagawa 215-8550 (Japan)] [Process Development Center, Canon ANELVA Corporation, Kurigi 2-5-1, Asao, Kawasaki, Kanagawa 215-8550 (Japan)

    2013-12-09T23:59:59.000Z

    We present time-resolved measurements of the displacement of magnetic domain-walls (DWs) driven by vertical spin-polarized currents in track-shaped magnetic tunnel junctions. In these structures, we observe very high DW velocities (600?m/s) at current densities below 10{sup 7}?A/cm{sup 2}. We show that the efficient spin-transfer torque combined with a short propagation distance allows avoiding the Walker breakdown process and achieving deterministic, reversible, and fast (?1?ns) DW-mediated switching of magnetic tunnel junction elements, which is of great interest for the implementation of fast DW-based spintronic devices.

  19. Pulsed Electrical Spin Injection into InGaAs Quantum Dots: Studies of the Electroluminescence Polarization Dynamics

    SciTech Connect (OSTI)

    Asshoff, P.; Loeffler, W.; Fluegge, H.; Zimmer, J.; Mueller, J.; Westenfelder, B.; Hu, D. Z.; Schaadt, D. M.; Kalt, H.; Hetterich, M. [Institut fuer Angewandte Physik and DFG Center for Functional Nanostructures (CFN), Universitaet Karlsruhe, 76131 Karlsruhe (Germany)

    2010-01-04T23:59:59.000Z

    We present time-resolved studies of the spin polarization dynamics during and after initialization through pulsed electrical spin injection into InGaAs quantum dots embedded in a p-i-n-type spin-injection light-emitting diode. Experiments are performed with pulse widths in the nanosecond range and a time-resolved single photon counting setup is used to detect the subsequent electroluminescence. We find evidence that the achieved spin polarization shows an unexpected temporal behavior, attributed mainly to many-carrier and non-equilibrium effects in the device.

  20. Evolution of the spin-state transition with doping in La??xSrxCoO?

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

    Smith, R. X.; Hoch, M. J. R.; Moulton, W. G.; Kuhns, P. L.; Reyes, A. P.; Boebinger, G. S.; Zheng, H.; Mitchell, J. F.

    2012-08-01T23:59:59.000Z

    The thermally induced spin-state transition of Co³? ions in the cobaltite LaCoO?, found at temperatures in the range 40 to 120 K, has been the subject of extensive experimental and theoretical investigation. Much less is known about what happens to the spin-state transition in hole-doped La??xSrxCoO? (LSCO). The present ¹³?La NMR experiments show that spin-state transitions persist in nanoscale hole-poor regions of the inhomogeneous doped material. In fact, thermally induced spin-state transitions remain important for doping levels close to the metal-insulator critical concentration of xC=0.17. This finding suggests that the unusual glassy behavior seen in doped LSCO for x<0.18 results from the interplay of spin-state transitions in hole-poor regions and ferromagnetism in hole-rich regions.