National Library of Energy BETA

Sample records for magnetic spin behavior

  1. Magnetic and dielectric behavior of the spin-chain compound Er?BaNiO? well below its Néel temperature

    SciTech Connect (OSTI)

    Basu, Tathamay; Singh, Kiran; Sampathkumaran, E. V.; Mohapatra, N.

    2014-09-21

    We have recently reported that the Haldane spin-chain system, Er?BaNiO?, 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.

  2. 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

  3. Effect of a high-frequency magnetic field on the resonant behavior displayed by a spin-$1/2$ particle under the influence of a rotating magnetic field

    E-Print Network [OSTI]

    Jesús Casado-Pascual

    2010-07-29

    In this paper, we investigate the role of a high-frequency magnetic field in the resonant behavior displayed by a spin-$1/2$ particle under the influence of a rotating magnetic field. We propose two alternative methods for analyzing the system dynamics, namely, the averaging method and the multiple scale method. The analytical results achieved by applying these two methods are compared with those obtained from the numerical solution of the Schr\\"odinger equation. This comparison leads to the conclusion that the multiple scale method provides a better understanding of the system dynamics than the averaging method. In particular, the averaging method predicts the complete destruction of the resonant behavior by an appropriate choice of the parameter values of the high-frequency magnetic field. This conclusion is disproved both by the numerical results, and also by the results obtained from the multiple scale method.

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

    SciTech Connect (OSTI)

    Mizrahi, M. E-mail: cabrera@fisica.unlp.edu.ar; Cabrera, A. F. E-mail: cabrera@fisica.unlp.edu.ar; Desimoni, J.; Stewart, S. J.

    2014-06-07

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

  5. Nonequilibrium Spin Magnetization Quantum Transport Equations

    E-Print Network [OSTI]

    Buot, F A; Otadoy, R E S; Villarin, D L

    2011-01-01

    The classical Bloch equations of spin magnetization transport is extended to fully time-dependent and highly-nonlinear nonequilibrium quantum distribution function (QDF) transport equations. The leading terms consist of the Boltzmann kinetic equation with spin-orbit coupling in a magnetic field together with spin-dependent scattering terms which do not have any classical analogue, but should incorporate the spatio-temporal-dependent phase-space dynamics of Elliot-Yafet and D'yakonov-Perel scatterings. The resulting magnetization QDF transport equation serves as a foundation for computational spintronic and nanomagnetic device applications, in performing simulation of ultrafast-switching-speed/low-power performance and reliability analyses.

  6. Spin ice: magnetic excitations without monopole signatures using muon spin rotation

    SciTech Connect (OSTI)

    Dunsiger, Sarah [Technical University, Munich, Germany; Aczel, Adam A. [McMaster University; Arguello, Carlos [Columbia University; Dabkowska, H. A. [McMaster University; Dabkowski, A [McMaster University; Du, Mao-Hua [ORNL; Goko, Tatsuo [Columbia University; Javanparast, B [University of Waterloo, Canada; Lin, T [University of Waterloo, Canada; Ning, F. L. [McMaster University; Noad, H. M. [McMaster University; Singh, David J [ORNL; Williams, T.J. [McMaster University; Uemura, Yasutomo J. [Columbia University; Gingras, M.P.J. [University of Waterloo, Canada; Luke, Graeme M. [McMaster University

    2011-01-01

    Theory predicts the low temperature magnetic excitations in spin ices consist of deconfined magnetic charges, or monopoles. A recent transverse-field (TF) muon spin rotation ({mu}SR) experiment [S.T. Bramwell et al., Nature (London) 461 956 (2009)] reports results claiming to be consistent with the temperature and magnetic field dependence anticipated for monopole nucleation - the so-called second Wien effect. We demonstrate via a new series of {mu}SR experiments in Dy{sub 2}Ti{sub 2}O{sub 7} that such an effect is not observable in a TF {mu}SR experiment. Rather, as found in many highly frustrated magnetic materials, we observe spin fluctuations which become temperature independent at low temperatures, behavior which dominates over any possible signature of thermally nucleated monopole excitations.

  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)

    2014-03-24

    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. Spin filtering in a ?-doped magnetic-electric-barrier nanostructure

    SciTech Connect (OSTI)

    Li, Shuai; Lu, Mao-Wang Jiang, Ya-Qing; Chen, Sai-Yan

    2014-09-15

    We report a theoretical study on spin-polarized transport in a ?-doped magnetic-electric-barrier nanostructure, which can be realized in experiments by depositing two ferromagnetic stripes on top and bottom of a semiconductor heterostructure under an applied voltage and by using atomic layer doping technique. The spin-polarized behavior of the electron in this device is found to be quite sensitive to the ?-doping. One can conveniently tune the degree of the electron spin polarization by adjusting the weight and/or position of the ?-doping. Thus, the involved nansosystem can be employed as a controllable spin filter, which may be helpful for exploiting new spin-polarized source for spintronics applications.

  9. Emergent spin electromagnetism induced by magnetization textures in the presence of spin-orbit interaction (invited)

    SciTech Connect (OSTI)

    Tatara, Gen; Nakabayashi, Noriyuki

    2014-05-07

    Emergent electromagnetic field which couples to electron's spin in ferromagnetic metals is theoretically studied. Rashba spin-orbit interaction induces spin electromagnetic field which is in the linear order in gradient of magnetization texture. The Rashba-induced effective electric and magnetic fields satisfy in the absence of spin relaxation the Maxwell's equations as in the charge-based electromagnetism. When spin relaxation is taken into account besides spin dynamics, a monopole current emerges generating spin motive force via the Faraday's induction law. The monopole is expected to play an important role in spin-charge conversion and in the integration of spintronics into electronics.

  10. Further Evidences for Spin Glass like behavior in NiO nanoparticles

    E-Print Network [OSTI]

    S. D. Tiwari; K. P. Rajeev

    2004-08-26

    Nickel oxide nanoparticles are prepared by a sol gel method and characterized by x-ray diffraction and transmission electron microscope. Here we present measurements on temperature and field dependence of magnetization and time dependence of thermoremanent magnetization. Our conclusion based on these measurements is that the system shows spin glass like behavior.

  11. Interfacial spin-filter assisted spin transfer torque effect in Co/BeO/Co magnetic tunnel junction

    SciTech Connect (OSTI)

    Tang, Y.-H. Chu, F.-C.

    2015-03-07

    The first-principles calculation is employed to demonstrate the spin-selective transport properties and the non-collinear spin-transfer torque (STT) effect in the newly proposed Co/BeO/Co magnetic tunnel junction. The subtle spin-polarized charge transfer solely at O/Co interface gives rise to the interfacial spin-filter (ISF) effect, which can be simulated within the tight binding model to verify the general expression of STT. This allows us to predict the asymmetric bias behavior of non-collinear STT directly via the interplay between the first-principles calculated spin current densities in collinear magnetic configurations. We believe that the ISF effect, introduced by the combination between wurtzite-BeO barrier and the fcc-Co electrode, may open a new and promising route in semiconductor-based spintronics applications.

  12. Tunable Polarization of Spin Polarized Current by Magnetic Field

    SciTech Connect (OSTI)

    Joo, S.; Kim, K.; Lee, J.; Kim, T.; Rhie, K.; Hong, J.; Shin, K-H.

    2010-10-10

    The spin polarization of a high g-factor bulk semiconductor is theoretically investigated in the presence of a magnetic field parallel to a driving electric field. Calculations have been carried out using the energy-dependent relaxation time approximation in association with spin-flip scattering. As the magnitude of the magnetic field increases, the spin-polarized current alternates between the spin-up and spin-down states for the low spin-scattering system. This implies that the current polarization can be tuned by controlling the magnetic field strength, suggesting possible applications to spintronic devices. An experimental method for investigating alternative current polarization is also considered.

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

    SciTech Connect (OSTI)

    Gofryk, K. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Jaime, M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). National High Magnetic Field Lab. (MagLab)

    2014-12-01

    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.

  14. Magnetization plateaus of dipolar spin ice on kagome lattice

    SciTech Connect (OSTI)

    Xie, Y. L.; Wang, Y. L.; Yan, Z. B.; Liu, J.-M.

    2014-05-07

    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.

  15. Electron spin magnetism of zigzag graphene nanoribbon edge states

    SciTech Connect (OSTI)

    Xu, Kun Ye, Peide D.

    2014-04-21

    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.

  16. Spin microscope based on optically detected magnetic resonance

    DOE Patents [OSTI]

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

    2010-06-29

    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.

  17. Spin microscope based on optically detected magnetic resonance

    DOE Patents [OSTI]

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

    2009-11-10

    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.

  18. Spin microscope based on optically detected magnetic resonance

    DOE Patents [OSTI]

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

    2007-12-11

    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.

  19. Spin microscope based on optically detected magnetic resonance

    DOE Patents [OSTI]

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

    2009-10-27

    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.

  20. Spin microscope based on optically detected magnetic resonance

    DOE Patents [OSTI]

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

    2010-07-13

    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.

  1. 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

  2. Collective Magnetic Behavior of Graphene Nanohole Superlattices Decai Yu, Elizabeth M. Lupton, Miao Liu, Wei Liu, and Feng Liu

    E-Print Network [OSTI]

    Simons, Jack

    Collective Magnetic Behavior of Graphene Nanohole Superlattices Decai Yu, Elizabeth M. Lupton, Miao "bulk" magnets--the graphene nanohole (GNH) superlattices with each GNH acting like a "super" magnetic for storage media and spintronics applications is discussed. KEYWORDS Graphene, magnetism, spin, magnetic

  3. 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

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

    E-Print Network [OSTI]

    S. Murugesh; M. Lakshmanan

    2009-10-20

    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.

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

    E-Print Network [OSTI]

    Debashree Chowdhury; Banasri Basu; Pratul Bandyopadhyay

    2015-02-25

    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.

  6. 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

  7. Waves of spin-current in magnetized dielectrics

    E-Print Network [OSTI]

    Andreev, P A

    2012-01-01

    Spin-current is the important physical quantity in present day spintronics and it might be very usefull in the physics of quantum plasma of spinning particles. Thus it is important to have an equation of spin-current dynamical evolution. This equation naturally appears as a part of a set of the quantum hydrodynamics (QHD) equations. Consequently, we present the set of the QHD equations derived from the many-particle microscopic Schrodinger equation, which consists of the continuity equation, the Euler equation, the Bloch equation and equation of spin-current evolution. We use these equations to study dispersion of collective excitations in three dimensional samples of magnetized dielectrics. We show that dynamics of spin-current leads to formation of new type of collective excitations in magnetized dielectrics, which we called spin-current waves.

  8. A cascade of magnetic field induced spin transitions in LaCoO{<_3}.

    SciTech Connect (OSTI)

    Altarawneh, M. M.; Chern, G.-W.; Harrison, N.; Batista, C. D.; Uchida, A.; Jaime, M.; Rickel, D. G.; Crooker, S. A.; Mielke, C. H.; Betts, J. B.; Mitchell, J. F.; Hoch, M. J. R. (Materials Science Division); (Los Alamos Nat. Lab.); (Mu'tah Univ.); (Florida State Univ.)

    2012-07-20

    We present magnetization and magnetostriction studies of LaCoO{sub 3} in magnetic fields approaching 100 T. In contrast with expectations from single-ion models, the data reveal two distinct first-order transitions and well-defined magnetization plateaus. The magnetization at the higher plateau is only about half the saturation value expected for spin-1 Co{sup 3+} ions. These findings strongly suggest collective behavior induced by interactions between different electronic configurations of Co{sup 3+} ions. We propose a model that predicts crystalline spin textures and a cascade of four magnetic phase transitions at high fields, of which the first two account for the experimental data.

  9. Sensitive Magnetic Control of Ensemble Nuclear Spin Hyperpolarisation in Diamond

    E-Print Network [OSTI]

    Wang, Hai-Jing; Avalos, Claudia E; Seltzer, Scott J; Budker, Dmitry; Pines, Alexander; Bajaj, Vikram S

    2012-01-01

    Dynamic nuclear polarisation, which transfers the spin polarisation of electrons to nuclei, is routinely applied to enhance the sensitivity of nuclear magnetic resonance; it is also critical in spintronics, particularly when spin hyperpolarisation can be produced and controlled optically or electrically. Here we show the complete polarisation of nuclei located near the optically-polarised nitrogen-vacancy (NV) centre in diamond. When approaching the ground-state level anti-crossing condition of the NV electron spins, 13C nuclei in the first-shell are polarised in a pattern that depends sensitively and sharply upon the magnetic field. Based on the anisotropy of the hyperfine coupling and of the optical polarisation mechanism, we predict and observe a complete reversal of the nuclear spin polarisation with a few-mT change in the magnetic field. The demonstrated sensitive magnetic control of nuclear polarisation at room temperature will be useful for sensitivity-enhanced NMR, nuclear-based spintronics, and quant...

  10. 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)

    2012-03-19

    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.

  11. Induced spin-accumulation and spin-polarization in a quantum-dot ring by using magnetic quantum dots and Rashba spin-orbit effect

    SciTech Connect (OSTI)

    Eslami, L., E-mail: Leslami@iust.ac.ir; Faizabadi, E. [School of Physics, Iran University of Science and Technology, Tehran 16846 (Iran, Islamic Republic of)

    2014-05-28

    The effect of magnetic contacts on spin-dependent electron transport and spin-accumulation in a quantum ring, which is threaded by a magnetic flux, is studied. The quantum ring is made up of four quantum dots, where two of them possess magnetic structure and other ones are subjected to the Rashba spin-orbit coupling. The magnetic quantum dots, referred to as magnetic quantum contacts, are connected to two external leads. Two different configurations of magnetic moments of the quantum contacts are considered; the parallel and the anti-parallel ones. When the magnetic moments are parallel, the degeneracy between the transmission coefficients of spin-up and spin-down electrons is lifted and the system can be adjusted to operate as a spin-filter. In addition, the accumulation of spin-up and spin-down electrons in non-magnetic quantum dots are different in the case of parallel magnetic moments. When the intra-dot Coulomb interaction is taken into account, we find that the electron interactions participate in separation between the accumulations of electrons with different spin directions in non-magnetic quantum dots. Furthermore, the spin-accumulation in non-magnetic quantum dots can be tuned in the both parallel and anti-parallel magnetic moments by adjusting the Rashba spin-orbit strength and the magnetic flux. Thus, the quantum ring with magnetic quantum contacts could be utilized to create tunable local magnetic moments which can be used in designing optimized nanodevices.

  12. Spin echo without an external permanent magnetic field

    E-Print Network [OSTI]

    Joakim Bergli; Leonid Glazman

    2006-09-19

    The spin echo techniques aim at the elimination of the effect of a random magnetic field on the spin evolution. These techniques conventionally utlize the application of a permanent field which is much stronger than the random one. The strong field, however, may also modify the magnetic response of the medium containing the spins, thus altering their ``natural'' dynamics. We suggest an iterative scheme for generating a sequence of pulses which create an echo without an external permanent field. The approximation to the ideal echo improves with the sequence length.

  13. Spin-stabilized magnetic levitation without vertical axis of rotation

    DOE Patents [OSTI]

    Romero, Louis (Albuquerque, NM); Christenson, Todd (Albuquerque, NM); Aaronson, Gene (Albuquerque, NM)

    2009-06-09

    The symmetry properties of a magnetic levitation arrangement are exploited to produce spin-stabilized magnetic levitation without aligning the rotational axis of the rotor with the direction of the force of gravity. The rotation of the rotor stabilizes perturbations directed parallel to the rotational axis.

  14. Hysteresis and compensation behaviors of spin-3/2 cylindrical Ising nanotube system

    SciTech Connect (OSTI)

    Kocakaplan, Yusuf; Keskin, Mustafa

    2014-09-07

    The hysteresis and compensation behaviors of the spin-3/2 cylindrical Ising nanotube system are studied within the framework of the effective-field theory with correlations. The effects of the Hamiltonian parameters are investigated on the magnetic and thermodynamic quantities, such as the total magnetization, hysteresis curves, and compensation behaviors of the system. Depending on the Hamiltonian parameters, some characteristic hysteresis behaviors are found, such as the existence of double and triple hysteresis loops. According to Néel classification nomenclature, the system displays Q-, R-, P-, N-, M-, and S- types of compensation behaviors for the appropriate values of the system parameters. We also compare our results with some recently published theoretical and experimental works and find a qualitatively good agreement.

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

    SciTech Connect (OSTI)

    Suzuki, Kosuke Takubo, Shota; Kato, Tadashi; Yamazoe, Masatoshi; Hoshi, Kazushi; Sakurai, Hiroshi; Homma, Yoshiya; Itou, Masayoshi; Sakurai, Yoshiharu

    2014-08-18

    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.

  16. Quantum chaos with spin-chains in pulsed magnetic fields

    E-Print Network [OSTI]

    T. Boness; M. M. A. Stocklin; T. S. Monteiro

    2006-12-11

    Recently it was found that the dynamics in a Heisenberg spin-chain subjected to a sequence of periodic pulses from an external, parabolic, magnetic field can have a close correspondence with the quantum kicked rotor (QKR). The QKR is a key paradigm of quantum chaos; it has as its classical limit the well-known Standard Map. It was found that a single spin excitation could be converted into a pair of non-dispersive, counter-propagating spin coherent states equivalent to the accelerator modes of the Standard Map. Here we consider how other types of quantum chaotic systems such as a double-kicked quantum rotor or a quantum rotor with a double-well potential might be realized with spin chains; we discuss the possibilities regarding manipulation of the one-magnon spin waves.

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

    SciTech Connect (OSTI)

    JOHNSON, P.D.; GUNTHERODT, G.

    2006-11-01

    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.

  18. Experimental investigation of magnetic anisotropy in spin vortex discs

    SciTech Connect (OSTI)

    Garraud, N. Arnold, D. P.

    2014-05-07

    We present experimental 2D vector vibrating sample magnetometer measurements to demonstrate the shape anisotropy effects occurring in micrometer-diameter supermalloy spin vortex discs. Measurements made for different disc sizes and orientations confirm the out-of-plane susceptibility is several orders of magnitude smaller than the in-plane susceptibility. These results validate with a high certitude that spin vortices with high diameter to thickness ratio retain in-plane-only magnetization, even when subjected to fields in the out-of-plane direction. These results contribute to further computational simulations of the dynamics of spin vortex structures in colloidal suspensions where external fields may be applied in any arbitrary direction.

  19. Invited review Spin transport in non-magnetic nano-structures induced by non-local

    E-Print Network [OSTI]

    Otani, Yoshichika

    ferromagnetic into non-magnetic metals. Analysis of spin relaxation length and time in Ag with the Elliot of the Elliot­Yafet mechanism based on spin­orbit interaction and momentum relaxation. The spin relaxation

  20. Spin glass behavior in FeAl2 

    E-Print Network [OSTI]

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

    2001-01-01

    and do not exhibit the be- havior attributed to rare-earth and actinide systems. FeAl2, however, clearly shows local-moment behavior leading to a spin-glass freezing at low temperatures. The resistivity of this material is large, comparable in size...

  1. Neutrino spin-flavor oscillations in rapidly varying magnetic fields

    E-Print Network [OSTI]

    Maxim Dvornikov

    2006-11-13

    The general formalism for the description of neutrino oscillations in arbitrary rapidly varying external fields is elaborated. We obtain the new effective Hamiltonian which determines the evolution of the averaged neutrino wave function. The general technique is applied to the neutrino oscillations in rapidly varying magnetic fields. We evaluate the transition probabilities of the neutrino spin-flavor oscillations in magnetic fields of the Sun and compare them with the numerical solutions of the Schroedinger equation with the exact Hamiltonian.

  2. Towards metallic magnetic memory: How to interpret experimental results on magnetic switching induced by spin-polarized currents

    SciTech Connect (OSTI)

    Bazaliy, Ya. B.; Jones, B. A.; Zhang, S. C.

    2001-06-01

    In the field of magnetic memory the giant magnetoresistance effect provides a convenient way to read out the state of a spin-valve type device by passing a small current through it. It is now debated whether passing a large current through such a device could reliably switch its magnetic state between parallel and antiparallel configurations thus turning a spin valve into a complete read{endash}write memory cell. Experiments with current induced switching were done by several groups, but their interpretation is not straightforward due to complicated interplay between the current-induced torques and those induced by anisotropy. We propose here an experimental setup where an exact solution for the switching behavior can be found in the framework of Slonczweski{close_quote}s approach. Comparison with experiment would be especially interesting since alternative approaches are discussed in the literature. {copyright} 2001 American Institute of Physics.

  3. Spin wave propagation in spatially nonuniform magnetic fields Kevin R. Smith,1,2,a

    E-Print Network [OSTI]

    Spin wave propagation in spatially nonuniform magnetic fields Kevin R. Smith,1,2,a Michael J August 2008 Spin wave pulse propagation in a magnetic thin film under static, spatially nonuniform strip. Spin wave pulses were excited with a microstrip transducer at one end of the film strip. The spin

  4. Electrically driven nuclear spin resonance in a single-molecule magnet

    E-Print Network [OSTI]

    Vallette, Bruno

    Electrically driven nuclear spin resonance in a single-molecule magnet Institut Néel : Nanospin Institut Néel, CNRS-UJF, Grenoble NanoSpin #12;· Molecular magnets are characterised by : a magnetic moment a strong uniaxial anisotropy Mn12 Molecular magnets Fe8 #12;· Molecular magnets are characterised

  5. Paramagnetism, superparamagnetism, and spin-glass behavior in bulk amorphous Pd{endash}Ni{endash}Fe{endash}P alloys

    SciTech Connect (OSTI)

    Shen, T.D.; Schwarz, R.B.; Thompson, J.D. [Materials Science and Technology Division, Mail Stop G755, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Materials Science and Technology Division, Mail Stop G755, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    1999-04-01

    We have investigated the magnetic properties of bulk amorphous Pd{sub 40}Ni{sub 40{minus}x}Fe{sub x}P{sub 20} (x=0{endash}17.5) alloys. For Pd{sub 40}Ni{sub 40}P{sub 20} (x=0), the magnetic susceptibility consists of temperature-independent and Curie{endash}Weiss-type terms. Alloys with x{ge}5 are paramagnetic at high temperatures. With decreasing temperature, the amorphous alloys become superparamagnetic. At even lower temperatures, and under a weak applied magnetic field, these alloys are spin glasses, as evidenced by static and dynamic magnetic measurements. The spin-freezing temperature increases with increasing iron content and this is attributed to the role of the Ruderman{endash}Kittel{endash}Kasuya{endash}Yosida interaction in creating the spin-glass state. The occurrence of a reentrant spin-glass behavior on cooling (superparamagnetism-to-ferromagnetism-to-spin-glass transition) is also observed for x=17.5 at a field {ge}50 Oe. An unexpected result is that the ferromagnetic state in the present bulk metallic glasses is {ital field induced}. Evidence for the field-induced ferromagnetic-like order is obtained from (a) straight regions in the susceptibility versus temperature curves measured at various fields, (b) an Arrott plot, and (c) time-independent magnetization. With increasing applied field, the spin-freezing temperature decreases and the Curie temperature increases, broadening the temperature range of the field-induced ferromagnetic-like state. The temporal decay of the thermoremanent magnetization in the amorphous alloy with x=17.5 is slower than that in typical crystalline spin glasses. The spin-freezing temperature of the amorphous alloy with x=17.5 decreases approximately logarithmically with applied field, which differs from the prediction of N{acute e}el{close_quote}s model for spin glasses. {copyright} {ital 1999 American Institute of Physics.}

  6. Spin current formation at the graphene/Pt interface for magnetization manipulation in magnetic nanodots

    SciTech Connect (OSTI)

    Shikin, A. M.; Rybkina, A. A.; Rybkin, A. G.; Klimovskikh, I. I.; Skirdkov, P. N.; Zvezdin, K. A.; Zvezdin, A. K.

    2014-07-28

    Spin electronic structure of the Graphene/Pt interface has been investigated. A large induced spin-orbit splitting (?80?meV) of graphene ? states with formation of non-degenerated Dirac-cone spin states at the K{sup ¯}-point of the Brillouin zone crossed with spin-polarized Pt 5d states at Fermi level was found. We show that this spin structure can be used as a spin current source in spintronic devices. By theoretical estimations and micromagnetic modeling based on the experimentally observed spin-orbit splitting, we demonstarte that the induced intrinsic magnetic field in such structure might be effectively used for induced remagnetization of the (Ni-Fe)-nanodots arranged atop the interface.

  7. Magnetization reversal driven by a spin torque oscillator

    SciTech Connect (OSTI)

    Sbiaa, R.

    2014-09-01

    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.

  8. Periodic magnetic structures generated by spin–polarized currents in nanostripes

    SciTech Connect (OSTI)

    Volkov, Oleksii M. Sheka, Denis D.; Kravchuk, Volodymyr P.; Gaididei, Yuri; Mertens, Franz G.

    2013-11-25

    The influence of a transverse spin–polarized current on long ferromagnetic nanostripes is studied numerically. The magnetization behavior is analyzed for all range of the applied currents, up to the saturation. It is shown that the saturation current is a nonmonotonic function of the stripe width. A number of stable periodic magnetization structures are observed below the saturation. Type of the periodical structure depends on the stripe width. Besides the one–dimensional domain structure, typical for narrow wires, and the two–dimensional vortex–antivortex lattice, typical for wide films, a number of intermediate structures are observed, e.g., cross–tie and diamond state.

  9. Spin-Hall-assisted magnetic random access memory

    SciTech Connect (OSTI)

    Brink, A. van den, E-mail: a.v.d.brink@tue.nl; Swagten, H. J. M.; Koopmans, B. [Physics of Nanostructures, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands)] [Physics of Nanostructures, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Cosemans, S.; Manfrini, M.; Van Roy, W.; Min, T. [imec, Kapeldreef 75, B-3001 Leuven (Belgium)] [imec, Kapeldreef 75, B-3001 Leuven (Belgium); Cornelissen, S.; Vaysset, A. [imec, Kapeldreef 75, B-3001 Leuven (Belgium) [imec, Kapeldreef 75, B-3001 Leuven (Belgium); Departement elektrotechniek (ESAT), KU Leuven, Kasteelpark Arenberg 10, B-3001 Heverlee (Belgium)

    2014-01-06

    We propose a write scheme for perpendicular spin-transfer torque magnetoresistive random-access memory that significantly reduces the required tunnel current density and write energy. A sub-nanosecond in-plane polarized spin current pulse is generated using the spin-Hall effect, disturbing the stable magnetic state. Subsequent switching using out-of-plane polarized spin current becomes highly efficient. Through evaluation of the Landau-Lifshitz-Gilbert equation, we quantitatively assess the viability of this write scheme for a wide range of system parameters. A typical example shows an eight-fold reduction in tunnel current density, corresponding to a fifty-fold reduction in write energy, while maintaining a 1?ns write time.

  10. 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)

    2014-05-15

    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.

  11. Entangled states, Lorentz transformations, Spin-precession in magnetic fields

    E-Print Network [OSTI]

    A. Chakrabarti

    2009-03-07

    Two positive mass, spin $\\frac 12$ particles created in an entangled state are studied in the presence of a constant magnetic field inducing distinct precessions, depending on the respective momenta, of the two spins. The charge and anomalous magnetic moment of each particle is taken into account. Consequences for entanglement and, more generally, on correlations, are derived. We start, however, with a compact derivation of the effects of Lorentz transformations on such entangled states, though that has been studied by several authors. Our formalism displays conveniently the analogies and the differences between the two cases. Moreover, combining the two, one obtains the case of constant, orthogonal electric and magnetic fields. More general perspectives are evoked in the concluding remarks.

  12. Origin of the positive spin- 12 photoluminescence-detected magnetic resonance in ?-conjugated materials and devices

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

    Chen, Ying; Cai, Min; Hellerich, Emily; Shinar, Ruth; Shinar, Joseph

    2015-09-02

    The spin-1/2 single-modulation (SM) and double-modulation (DM) photoluminescence (PL) detected magnetic resonance (PLDMR) in poly(2-methoxy-5-(2'-ethyl)–hexoxy-1,4- phenylene vinylene) (MEH-PPV) films and poly(3-hexylthiophene) (P3HT) films is described, analyzed, and discussed. In particular, the models based on spin-dependent recombination of charge pairs (SDR) and triplet-polaron quenching (TPQ) are evaluated. By analyzing the dependence of the resonance amplitude on the microwave chopping (modulation) frequency using rate equations, it is demonstrated that the TPQ model can well explain the observed resonance behavior, while SDR model cannot reproduce the results of the observed DM-PLDMR. As a result, the observed spin-1/2 PLDMR is assigned to TPQ rathermore »than SDR, even though the latter may also be present.« less

  13. 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

  14. Quantitative analysis of magnetic spin and orbital moments from an oxidized iron (1 1 0) surface using electron magnetic circular dichroism

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

    Thersleff, Thomas; Rusz, Jan; Rubino, Stefano; Hjörvarsson, Björgvin; Ito, Yasuo; J. Zaluzec, Nestor; Leifer, Klaus

    2015-08-17

    Understanding the ramifications of reduced crystalline symmetry on magnetic behavior is a critical step in improving our understanding of nanoscale and interfacial magnetism. However, investigations of such effects are often controversial largely due to the challenges inherent in directly correlating nanoscale stoichiometry and structure to magnetic behavior. Here, we describe how to use Transmission Electron Microscope (TEM) to obtain Electron Magnetic Circular Dichroism (EMCD) signals as a function of scattering angle to locally probe the magnetic behavior of thin oxide layers grown on an Fe (1 1 0) surface. Experiments and simulations both reveal a strong dependence of the magneticmore »orbital to spin ratio on its scattering vector in reciprocal space. We exploit this variation to extract the magnetic properties of the oxide cladding layer, showing that it locally may exhibit an enhanced orbital to spin moment ratio. This finding is supported here by both spatially and angularly resolved EMCD measurements, opening up the way for compelling investigations into how magnetic properties are affected by nanoscale features.« less

  15. Charge and Spin Transport in Dilute Magnetic Semiconductors

    SciTech Connect (OSTI)

    Ullrich, Carsten A.

    2009-07-23

    This proposal to the DOE outlines a three-year plan of research in theoretical and computational condensed-matter physics, with the aim of developing a microscopic theory for charge and spin dynamics in disordered materials with magnetic impurities. Important representatives of this class of materials are the dilute magnetic semiconductors (DMS), which have attracted great attention as a promising basis for spintronics devices. There is an intense experimental effort underway to study the transport properties of ferromagnetic DMS such as (Ga,Mn)As, and a number of interesting features have emerged: negative magnetoresistance, anomalous Hall effect, non-Drude dynamical conductivity, and resistivity maxima at the Curie temperature. Available theories have been able to account for some of these features, but at present we are still far away from a systematic microscopic understanding of transport in DMS. We propose to address this challenge by developing a theory of charge and spin dynamics based on a combination of the memory-function formalism and time-dependent density functional theory. This approach will be capable of dealing with two important issues: (a) the strong degree of correlated disorder in DMS, close to the localization transition (which invalidates the usual relaxation-time approximation to the Boltzmann equation), (b) the essentially unknown role of dynamical many-body effects such as spin Coulomb drag. We will calculate static and dynamical conductivities in DMS as functions of magnetic order and carrier density, which will advance our understanding of recent transport and infrared absorption measurements. Furthermore, we will study collective plasmon excitations in DMS (3D, 2D and quantum wells), whose linewidths could constitute a new experimental probe of the correlation of disorder, many-body effects and charge and spin dynamics in these materials.

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

    E-Print Network [OSTI]

    Yeh, Nai-Chang

    Spin and Charge Quantum Transport in Organic/Magnetic Heterostructures for Spintronics to optimizing the spintronic and optoelectronic properties of organic semiconductor/ferromagnet heterostructures. "Spintronics" is a new electronics paradigm based on manipulation and detection of the spin

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

    E-Print Network [OSTI]

    Cappellaro, Paola

    2014-01-01

    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 ...

  18. 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)

    2014-07-21

    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.

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

    SciTech Connect (OSTI)

    Mcdonald, Ross D; Singleton, John; Lancaster, Tom; Goddard, Paul; Manson, Jamie

    2011-01-14

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

  20. Electric and magnetic behaviors observed in NiO-based thin films under light-irradiation

    SciTech Connect (OSTI)

    Luo, Yi-Dong; Song, Kenan; Shun, Li; Gao, Junqi; Xu, Ben, E-mail: xuben@mail.tsinghua.edu.cn, E-mail: linyh@mail.tsinghua.edu.cn; Lin, Yuan-Hua, E-mail: xuben@mail.tsinghua.edu.cn, E-mail: linyh@mail.tsinghua.edu.cn; Nan, Ce-Wen; Liu, Wei [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2014-09-07

    We report the room-temperature ferromagnetic properties that can be tuned by light irradiation in the Li and Mn co-doped NiO films (LMNO) grown by the spinning coating. The optical tunable magnetic behavior is enhanced by the increase of the Li doping concentration. First-principle calculations reveal that the Li doping plays key roles in the optical tuned magnetic behavior, which brings a 3d-like impurity state to enhance a significant hybridization between the Mn{sup 3+} 3d state and the impurity band, thus strengthening the ferromagnetic coupling effects. Additionally, it can tune the band gap of the LMNO films and produce more holes under the light irradiation, enhancing the optical tuned magnetic behavior.

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

    E-Print Network [OSTI]

    D. B. Papadopoulos

    2003-12-23

    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.

  2. 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

  3. 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

  4. 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

  5. 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.

    2015-02-01

    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

  6. Origin of spin gapless semiconductor behavior in CoFeCrGa. Theory and Experiment

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

    Bainsla, Lakhan; Mallick, A. I.; Raja, M. Manivel; Coelho, A. A.; Nigam, A. K.; Johnson, D. D.; Alam, Aftab; Suresh, K. G.

    2015-07-08

    Despite a plethora of materials suggested for spintronic applications, a new class of materials has emerged, namely spin gapless semiconductors (SGS), which offers potentially more advantageous properties than existing ones. These magnetic semiconductors exhibit a finite band gap for one spin channel and a closed gap for the other. Supported by electronic-structure calculations, we report evidence of SGS behavior in equiatomic quaternary CoFeCrGa, having a cubic Heusler (prototype LiMgPdSn) structure but exhibiting chemical disorder (DO3 structure). CoFeCrGa is found to transform from SGS to half-metallic phase under pressure, which is attributed to unique electronic-structure features. The saturation magnetization (MS) wasmore »obtained at 8K agrees with the Slater-Pauling rule and the Curie temperature (TC) is found to exceed 400K. Carrier concentration (up to 250K) and electrical conductivity are observed to be nearly temperature independent, prerequisites for SGS. The anomalous Hall coefficient is estimated to be 185S/cm at 5K. Considering the SGS properties and high TC, this material appears to be promising for spintronic applications.« less

  7. Origin of spin gapless semiconductor behavior in CoFeCrGa. Theory and Experiment

    SciTech Connect (OSTI)

    Bainsla, Lakhan; Mallick, A. I.; Raja, M. Manivel; Coelho, A. A.; Nigam, A. K.; Johnson, D. D.; Alam, Aftab; Suresh, K. G.

    2015-07-08

    Despite a plethora of materials suggested for spintronic applications, a new class of materials has emerged, namely spin gapless semiconductors (SGS), which offers potentially more advantageous properties than existing ones. These magnetic semiconductors exhibit a finite band gap for one spin channel and a closed gap for the other. Supported by electronic-structure calculations, we report evidence of SGS behavior in equiatomic quaternary CoFeCrGa, having a cubic Heusler (prototype LiMgPdSn) structure but exhibiting chemical disorder (DO3 structure). CoFeCrGa is found to transform from SGS to half-metallic phase under pressure, which is attributed to unique electronic-structure features. The saturation magnetization (MS) was obtained at 8K agrees with the Slater-Pauling rule and the Curie temperature (TC) is found to exceed 400K. Carrier concentration (up to 250K) and electrical conductivity are observed to be nearly temperature independent, prerequisites for SGS. The anomalous Hall coefficient is estimated to be 185S/cm at 5K. Considering the SGS properties and high TC, this material appears to be promising for spintronic applications.

  8. 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

    2015-03-13

    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 (fields of 3 T. In addition, we demonstrate coherent control of single nuclear spins under these conditions. Furthermore, our results extend the applicable magnetic field range of a single spin magnetic field 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.

  9. Magnetic Materials at finite Temperatures: thermodynamics and combined spin and molecular dynamics derived from first principles calculations

    SciTech Connect (OSTI)

    Eisenbach, Markus; Perera, Meewanage Dilina N; Landau, David P; Nicholson, Don M; Yin, Junqi; Brown, Greg

    2015-01-01

    We present a unified approach to describe the combined behavior of the atomic and magnetic degrees of freedom in magnetic materials. Using Monte Carlo simulations directly combined with first principles the Curie temperature can be obtained ab initio in good agreement with experimental values. The large scale constrained first principles calculations have been used to construct effective potentials for both the atomic and magnetic degrees of freedom that allow the unified study of influence of phonon-magnon coupling on the thermodynamics and dynamics of magnetic systems. The MC calculations predict the specific heat of iron in near perfect agreement with experimental results from 300K to above Tc and allow the identification of the importance of the magnon-phonon interaction at the phase-transition. Further Molecular Dynamics and Spin Dynamics calculations elucidate the dynamics of this coupling and open the potential for quantitative and predictive descriptions of dynamic structure factors in magnetic materials using first principles derived simulations.

  10. Manipulation of the magnetic state of a small ferromagnetic particle by means of nonlocal spin-injection techniques ,,invited...

    E-Print Network [OSTI]

    Otani, Yoshichika

    at the cross so that, un- like the direct spin-injection device Fig.1 b , only the spin current can reachManipulation of the magnetic state of a small ferromagnetic particle by means of nonlocal spin-injection is used for spin current injection into a nanoscale ferromagnetic particle to reverse its magnetization

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

    SciTech Connect (OSTI)

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

    2014-10-15

    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.

  12. 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)

    2014-07-28

    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.

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

    SciTech Connect (OSTI)

    Ono, K. Inami, N.; Saito, K.; Takeichi, Y.; Kawana, D.; Yokoo, T.; Itoh, S.; Yano, M.; Shoji, T.; Manabe, A.; Kato, A.; Kaneko, Y.

    2014-05-07

    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)

  14. The effect of a magnetic field on the spin-selective transport in double-stranded DNA

    SciTech Connect (OSTI)

    Simchi, Hamidreza; Esmaeilzadeh, Mahdi Mazidabadi, Hossein

    2014-05-28

    Spin-polarization in double-stranded DNA is studied in the presence of a magnetic field applied along its helix axis using the non-equilibrium Green's function method. The spin-polarization could be tuned by changing the magnetic field. In some special cases, the double-stranded DNA behaved as a perfect spin-filter. Furthermore, the dependency of the spin-polarization on the spin-orbit strength and dephasing strength is studied.

  15. Polaron Behavior in CMR Manganites

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

    Manganites Polaron Behavior in CMR Manganites Print Wednesday, 26 January 2005 00:00 Spintronic devices manipulate electron spin to sense magnetic fields, store information, or...

  16. Dynamic control of spin states in interacting magnetic elements

    DOE Patents [OSTI]

    Jain, Shikha; Novosad, Valentyn

    2014-10-07

    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.

  17. Mode-hopping mechanism generating colored noise in a magnetic tunnel junction based spin torque oscillator

    SciTech Connect (OSTI)

    Sharma, Raghav; Dürrenfeld, P.; Iacocca, E.; Heinonen, O. G.; Åkerman, J.; Muduli, P. K.

    2014-09-29

    The frequency noise spectrum of a magnetic tunnel junction based spin torque oscillator is examined where multiple modes and mode-hopping events are observed. The frequency noise spectrum is found to consist of both white noise and 1/f frequency noise. We find a systematic and similar dependence of both white noise and 1/f frequency noise on bias current and the relative angle between the reference and free layers, which changes the effective damping and hence the mode-hopping behavior in this system. The frequency at which the 1/f frequency noise changes to white noise increases as the free layer is aligned away from the anti-parallel orientation w.r.t the reference layer. These results indicate that the origin of 1/f frequency noise is related to mode-hopping, which produces both white noise as well as 1/f frequency noise similar to the case of ring lasers.

  18. Emergence of classical behavior from the quantum spin

    E-Print Network [OSTI]

    M. Radonjic; S. Prvanovic; N. Buric

    2012-02-09

    Classical Hamiltonian system of a point moving on a sphere of fixed radius is shown to emerge from the constrained evolution of quantum spin. The constrained quantum evolution corresponds to an appropriate coarse-graining of the quantum states into equivalence classes, and forces the equivalence classes to evolve as single units representing the classical states. The coarse-grained quantum spin with the constrained evolution in the limit of the large spin becomes indistinguishable from the classical system.

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

    E-Print Network [OSTI]

    Khushrushahi, Shahriar Rohinton

    2010-01-01

    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 ...

  20. Nonadiabatic Spin Torque Investigated Using Thermally Activated Magnetic Domain Wall Dynamics

    E-Print Network [OSTI]

    Dunin-Borkowski, Rafal E.

    Nonadiabatic Spin Torque Investigated Using Thermally Activated Magnetic Domain Wall Dynamics M microscopy, we investigate the thermally activated motion of domain walls (DWs) between two positions properly analyzed, thermally activated processes at tem- peratures even well below the Curie temperature

  1. Predicting Magnetic Behavior in Copper Oxide Superconductors...

    Office of Science (SC) Website

    and showed good agreement between the theoretical data and those obtained from neutron scattering and magnetic susceptibility measurements. The research used highly...

  2. Generation of a spin-polarized electron beam by multipole magnetic fields

    E-Print Network [OSTI]

    Boyd, Robert W.

    Generation of a spin-polarized electron beam by multipole magnetic fields Ebrahim Karimi a October 2013 Accepted 18 December 2013 Available online 31 December 2013 Keywords: Electron vortex beam Polarized electron beam Spin-to-orbit conversion a b s t r a c t The propagation of an electron beam

  3. 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

  4. Microscopic studies of nonlocal spin dynamics and spin transport (invited)

    SciTech Connect (OSTI)

    Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris

    2015-05-07

    Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

  5. Synchronization of an array of spin torque nano oscillators in periodic applied external magnetic field

    E-Print Network [OSTI]

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

    2013-04-03

    Considering an array of spin torque transfer nano oscillators (STNOs), we have investigated the synchronization property of the system under the action of a common periodically driven applied external magnetic field by numerically analyzing the underlying system of Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equations for the macro-spin variables. We find the novel result that the applied external magnetic field can act as a medium to induce synchronization of periodic oscillations, both in-phase and anti-phase, even without coupling through spin current, thereby leading to the exciting possibility of enhancement of microwave power in a straightforward way.

  6. Unidirectional propagation of magnetostatic surface spin waves at a magnetic film surface

    SciTech Connect (OSTI)

    Wong, Kin L.; Bao, Mingqiang E-mail: caross@mit.edu; Lin, Yen-Ting; Wang, Kang L.; Bi, Lei; Wen, Qiye; Zhang, Huaiwu; Chatelon, Jean Pierre; Ross, C. A. E-mail: caross@mit.edu

    2014-12-08

    An analytical expression for the amplitudes of magnetostatic surface spin waves (MSSWs) propagating in opposite directions at a magnetic film surface is presented. This shows that for a given magnetic field H, it is forbidden for an independent MSSW to propagate along the direction of ?H{sup ?}×n{sup ?}, where n{sup ?} is the surface normal. This unidirectional propagation property is confirmed by experiments with both permalloy and yttrium iron garnet films of different film thicknesses, and has implications in the design of spin-wave devices such as isolators and spin-wave diodes.

  7. Charge-induced spin polarization in non-magnetic organic molecule Alq$_{3}$

    E-Print Network [OSTI]

    Tarafder, Kartick; Oppeneer, Peter

    2010-01-01

    Electrical injection in organic semiconductors is a key prerequisite for the realization of organic spintronics. Using density-functional theory calculations we report the effect of electron transfer into the organic molecule Alq$_3$. Our first-principles simulations show that electron injection spontaneously spin-polarizes non-magnetic Alq$_3$ with a magnetic moment linearly increasing with induced charge. An asymmetry of the Al--N bond lengths leads to an asymmetric distribution of injected charge over the molecule. The spin-polarization arises from a filling of dominantly the nitrogen $p_z$ orbitals in the molecule's LUMO together with ferromagnetic coupling of the spins on the quinoline rings.

  8. Recursive polarization of nuclear spins in diamond at arbitrary magnetic fields

    SciTech Connect (OSTI)

    Pagliero, Daniela; Laraoui, Abdelghani; Henshaw, Jacob D.; Meriles, Carlos A.

    2014-12-15

    We introduce an alternate route to dynamically polarize the nuclear spin host of nitrogen-vacancy (NV) centers in diamond. Our approach articulates optical, microwave, and radio-frequency pulses to recursively transfer spin polarization from the NV electronic spin. Using two complementary variants of the same underlying principle, we demonstrate nitrogen nuclear spin initialization approaching 80% at room temperature both in ensemble and single NV centers. Unlike existing schemes, our approach does not rely on level anti-crossings and is thus applicable at arbitrary magnetic fields. This versatility should prove useful in applications ranging from nanoscale metrology to sensitivity-enhanced NMR.

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

    E-Print Network [OSTI]

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

    2013-06-10

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

  10. Spin Torques in Magnetic and Superconducting Tunnel Junctions

    E-Print Network [OSTI]

    Hoffman, Silas Eli

    2012-01-01

    Proximity Effects at Superconducting Interfaces . . . . . .of spin-triplet superconductivity in Co-based JosephsonExchange Field in Superconductor- Ferromagnet Structures. ”

  11. PHYSICAL REVIEW B 85, 184301 (2012) Spin-lattice-electron dynamics simulations of magnetic materials

    E-Print Network [OSTI]

    2012-01-01

    of experiments on laser-induced demagnetization of iron thin films, and estimate the rates of heat transfer of a magnetic material. They evaluated the total free energies and heat capacities of Fe, Co, and Ni usingPHYSICAL REVIEW B 85, 184301 (2012) Spin-lattice-electron dynamics simulations of magnetic

  12. 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

  13. Cancellation of orbital and spin magnetism in UFe/sub 2/

    SciTech Connect (OSTI)

    Wulff, M.; Lander, G.H.; Lebech, B.; Delapalme, A.

    1989-03-01

    Polarized-neutron measurements have shown that the orbital and spin magnetic moments, which individually have a value of approx.0.23..mu../sub B/, almost completely cancel on the U sublattice in the ordered Laves phase UFe/sub 2/. This confirms a recent theoretical predicton and raises the possibility of ''magnetic'' compounds with zero total moment.

  14. Magneto-optical imaging of thin magnetic films using spins in diamond

    E-Print Network [OSTI]

    David A. Simpson; Jean-Philippe Tetienne; Julia McCoey; Kumaravelu Ganesan; Liam T. Hall; Steven Petrou; Robert E. Scholten; Lloyd C. L. Hollenberg

    2015-08-10

    Imaging the fields of magnetic materials provides crucial insight into the physical and chemical processes surrounding magnetism, and has been a key ingredient in the spectacular development of magnetic data storage. Existing approaches using the magneto-optic Kerr effect (MOKE), x-ray and electron microscopy have limitations that constrain further development, and there is increasing demand for imaging and characterisation of magnetic phenomena in real time with high spatial resolution. In this work, we show how the magneto-optical response of an array of negatively-charged nitrogen-vacancy spins in diamond can be used to image and map the sub-micron stray magnetic field patterns from thin ferromagnetic films. Using optically detected magnetic resonance, we demonstrate wide-field magnetic imaging over 100x100 {\\mu}m^2 with a diffraction-limited spatial resolution of 440 nm at video frame rates, under ambient conditions. We demonstrate a novel all-optical spin relaxation contrast imaging approach which can image magnetic structures in the absence of an applied microwave field. Straightforward extensions promise imaging with sub-{\\mu}T sensitivity and sub-optical spatial and millisecond temporal resolution. This work establishes practical diamond-based wide-field microscopy for rapid high-sensitivity characterisation and imaging of magnetic samples, with the capability for investigating magnetic phenomena such as domain wall and skyrmion dynamics and the spin Hall effect in metals.

  15. Magnetic vortex crystal formation in the antidot complement of square artificial spin ice

    SciTech Connect (OSTI)

    Araujo, C. I. L. de Silva, R. C.; Ribeiro, I. R. B.; Nascimento, F. S.; Felix, J. F.; Ferreira, S. O.; Moura-Melo, W. A.; Pereira, A. R.; Mól, L. A. S.

    2014-03-03

    We have studied ferromagnetic nickel thin films patterned with square lattices of elongated antidots that are negative analogues of square artificial spin ice. Micromagnetic simulations and direct current magnetic moment measurements reveal in-plane anisotropy of the magnetic hysteresis loops, and the formation of a dense array of magnetic vortices with random polarization and chirality. These multiply-connected antidot arrays could be superior to lattices of disconnected nanodisks for investigations of vortex switching by applied electric current.

  16. 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.; Dal Savio, C.; Karrai, K.; Dantelle, G.; Thiaville, A.; Rohart, S.

    2012-04-09

    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.

  17. SPIN EVOLUTION OF ACCRETING YOUNG STARS. I. EFFECT OF MAGNETIC STAR-DISK COUPLING

    SciTech Connect (OSTI)

    Matt, Sean P.; Greene, Thomas P.; Pinzon, Giovanni; De la Reza, Ramiro E-mail: thomas.p.greene@nasa.go E-mail: delareza@on.b

    2010-05-10

    We present a model for the rotational evolution of a young, solar mass star interacting with an accretion disk. The model incorporates a description of the angular momentum transfer between the star and the disk due to a magnetic connection, and includes changes in the star's mass and radius and a decreasing accretion rate. The model also includes, for the first time in a spin evolution model, the opening of the stellar magnetic field lines, as expected to arise from twisting via star-disk differential rotation. In order to isolate the effect that this has on the star-disk interaction torques, we neglect the influence of torques that may arise from open field regions connected to the star or disk. For a range of magnetic field strengths, accretion rates, and initial spin rates, we compute the stellar spin rates of pre-main-sequence stars as they evolve on the Hayashi track to an age of 3 Myr. How much the field opening affects the spin depends on the strength of the coupling of the magnetic field to the disk. For the relatively strong coupling (i.e., high magnetic Reynolds number) expected in real systems, all models predict spin periods of less than {approx}3 days, in the age range of 1-3 Myr. Furthermore, these systems typically do not reach an equilibrium spin rate within 3 Myr, so that the spin at any given time depends upon the choice of initial spin rate. This corroborates earlier suggestions that, in order to explain the full range of observed rotation periods of approximately 1-10 days, additional processes, such as the angular momentum loss from powerful stellar winds, are necessary.

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

    SciTech Connect (OSTI)

    Kollu, Pratap E-mail: anirmalagrace@vit.ac.in; Prathapani, Sateesh; Varaprasadarao, Eswara K.; Mallick, Sudhanshu; Bahadur, D. E-mail: anirmalagrace@vit.ac.in; Santosh, Chella; Grace, Andrews Nirmala E-mail: anirmalagrace@vit.ac.in

    2014-08-04

    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.

  19. Magnetic defects in chemically converted graphene nanoribbons: electron spin resonance investigation

    SciTech Connect (OSTI)

    Singamaneni, Srinivasa Rao; Stesmans, Andre; Tol, Johan van; Kosynkin, D. V.; Tour, James M.; Department of Mechanical Engineering and Materials Science, Smalley Institute for Nanoscale Science and Technology, Rice University, MS-222, 6100 Main Street, Houston, Texas 77005; Smalley Institute for Nanoscale Science and Technology, Rice University, MS-222, 6100 Main Street, Houston, Texas 77005, USA.

    2014-04-15

    Electronic spin transport properties of graphene nanoribbons (GNRs) are influenced by the presence of adatoms, adsorbates and edge functionalization. To improve the understanding of the factors that influence the spin properties of GNRs, local (element) spin-sensitive techniques such as electron spin resonance (ESR) spectroscopy are important for spintronics applications. Here, we present results of multi-frequency continuous wave (CW), pulse and hyperfine sublevel correlation (HYSCORE) ESR spectroscopy measurements performed on oxidatively unzipped graphene nanoribbons (GNRs), which were subsequently chemically converted (CCGNRs) with hydrazine. ESR spectra at 336 GHz reveal an isotropic ESR signal from the CCGNRs, of which the temperature dependence of its line width indicates the presence of localized unpaired electronic states. Upon functionalization of CCGNRs with 4-nitrobenzene diazonium tetrafluoroborate, the ESR signal is found to be 2 times narrower than that of pristine ribbons. NH{sub 3} adsorption/desorption on CCGNRs is shown to narrow the signal, while retaining the signal intensity and g value. The electron spin-spin relaxation process at 10 K is found to be characterized by slow (163 ns) and fast (39 ns) components. HYSCORE ESR data demonstrate the explicit presence of protons and {sup 13}C atoms. With the provided identification of intrinsic point magnetic defects such as proton and {sup 13}C has been reported, which are roadblocks to spin travel in graphene-based materials, this work could help in advancing the present fundamental understanding on the edge-spin (or magnetic)-based transport properties of CCGNRs.

  20. 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

    2015-01-01

    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...

  1. Critical behavior and universality in Levy spin glasses 

    E-Print Network [OSTI]

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

    2011-01-01

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

  2. Magnetization switching in a CoFeB/MgO magnetic tunnel junction by combining spin-transfer torque and electric field-effect

    SciTech Connect (OSTI)

    Kanai, S.; Nakatani, Y.; Yamanouchi, M.; Ikeda, S.; Sato, H.; Matsukura, F.; Ohno, H.

    2014-05-26

    We propose and demonstrate a scheme for magnetization switching in magnetic tunnel junctions, in which two successive voltage pulses are applied to utilize both spin-transfer torque and electric field effect. Under this switching scheme, a CoFeB/MgO magnetic tunnel junction with perpendicular magnetic easy axis is shown to switch faster than by spin-transfer torque alone and more reliably than that by electric fields alone.

  3. Three-dimensional magnetic spin-echo small-angle neutron scattering and neutron depolarization: A comparison

    SciTech Connect (OSTI)

    Rekveldt, M. Theo; Dijk, Niels H. van; Grigoriev, Serguei V.; Kraan, Wicher H.; Bouwman, Wim G. [Department of Radiation, Radionuclides and Reactors, Faculty of Applied Sciences, Delft University of Technology, 2629 JB Delft (Netherlands); Petersburg Nuclear Physics Institute, 188300 Gatchina, St-Petersburg District (Russian Federation); Department of Radiation, Radionuclides and Reactors, Faculty of Applied Sciences, Delft University of Technology, 2629 JB Delft (Netherlands)

    2006-07-15

    The recently developed magnetic spin-echo small-angle neutron scattering (SANS) technique provides unique information about the distance correlation of the local vector magnetization as a function of the spin-echo length within a magnetic material. The technique probes the magnetic correlations on a length scale from 10 nm up to 10 {mu}m within the bulk of a magnetic material by evaluating the Larmor precession of a polarized neutron beam in a spin-echo setup. The characteristics of the spin-echo SANS technique are discussed and compared to those of the more conventional neutron depolarization technique. Both of these techniques probe the average size of the magnetic inhomogeneities and the local magnetic texture. The magnetic spin-echo SANS technique gives information on the size distribution of these magnetic inhomogeneities perpendicular to the beam and, in principle, independent on the local magnetic induction. This information is not accessible by the neutron depolarization technique that gives the average size parallel to the beam multiplied with the square of the local magnetic induction. The basic possibilities of the magnetic spin-echo SANS technique are demonstrated by experiments on samples with a strong magnetic texture.

  4. Nuclear-electronic spin systems, magnetic resonance, and quantum information processing

    E-Print Network [OSTI]

    M. H. Mohammady

    2013-05-04

    A promising platform for quantum information processing is that of silicon impurities, where the quantum states are manipulated by magnetic resonance. Such systems, in abstraction, can be considered as a nucleus of arbitrary spin coupled to an electron of spin one-half via an isotropic hyperfine interaction. We therefore refer to them as "nuclear-electronic spin systems". The traditional example, being subject to intensive experimental studies, is that of phosphorus doped silicon (Si:P) which couples a spin one-half electron to a nucleus of the same spin, with a hyperfine strength of 117.5 MHz. More recently, bismuth doped silicon (Si:Bi) has been suggested as an alternative instantiation of nuclear-electronic spin systems, differing from Si:P by its larger nuclear spin and hyperfine strength of 9/2 and 1.4754 GHz respectively. The aim of this thesis has been to develop a model that is capable of predicting the magnetic resonance properties of nuclear-electronic spin systems. The theoretical predictions of this model have been tested against experimental data collected on Si:Bi at 4.044 GHz, and have proven quite successful. Furthermore, the larger nuclear spin and hyperfine strength of Si:Bi, compared with that of Si:P, are predicted to offer advantages for quantum information processing. Most notable amongst these is that magnetic field-dependent two-dimensional decoherence free subspaces, called optimal working points, have been identified to exist in Si:Bi, but not Si:P.

  5. 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

    2015-04-19

    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.

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

    E-Print Network [OSTI]

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

    2003-07-09

    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.

  7. 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)

    2014-08-28

    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.

  8. Anomalous magnetic structure and spin dynamics in magnetoelectric LiFePO4

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

    Toft-Petersen, Rasmus; Reehuis, Manfred; Jensen, Thomas B. S.; Andersen, Niels H.; Li, Jiying; Le, Manh Duc; Laver, Mark; Niedermayer, Christof; Klemke, Bastian; Lefmann, Kim; et al

    2015-07-06

    We report significant details of the magnetic structure and spin dynamics of LiFePO4 obtained by single-crystal neutron scattering. Our results confirm a previously reported collinear rotation of the spins away from the principal b axis, and they determine that the rotation is toward the a axis. In addition, we find a significant spin-canting component along c. Furthermore, the possible causes of these components are discussed, and their significance for the magnetoelectric effect is analyzed. Inelastic neutron scattering along the three principal directions reveals a highly anisotropic hard plane consistent with earlier susceptibility measurements. While using a spin Hamiltonian, we showmore »that the spin dimensionality is intermediate between XY- and Ising-like, with an easy b axis and a hard c axis. It is shown that both next-nearest neighbor exchange couplings in the bc plane are in competition with the strongest nearest neighbor coupling.« less

  9. Magnetic-Compton-scattering study of spin moments in UFe{sub 2}

    SciTech Connect (OSTI)

    Lawson, P.K.; Cooper, M.J.; Dixon, M.A.; Timms, D.N.; Zukowski, E.; Itoh, F.; Sakurai, H.

    1997-08-01

    Spin moments were derived from the magnetic-Compton profile of UFe{sub 2}, which was measured using 59.38-keV circularly polarized synchrotron radiation from the Accumulation Ring Source at KEK, Japan. Although the net moment on the uranium site is no more than a tenth of a Bohr magneton, the individual spin and orbital moments, which are coupled antiparallel, are much larger and it is the spin moment that can be determined in magnetic-Compton scattering. The data have been analyzed in terms of the U 5f, Fe 3d and delocalized spin moments. The observed uranium-5f spin moment is less than half (i.e., {lt}0.25{mu}{sub B}) and the diffuse spin moment more than double (i.e., {gt}0.20{mu}{sub B}) those predicted from theory. These values compare favorably with those deduced from neutron measurements of the total magnetization. {copyright} {ital 1997} {ital The American Physical Society}

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

    E-Print Network [OSTI]

    I. Vidaña; A. Polls; A. Ramos

    2001-11-19

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

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

    SciTech Connect (OSTI)

    Santos, T. S.; Moodera, J. S.; Venkataraman, K.; Negusse, E.; Holroyd, J.; Dvorak, J.; Liberati, M.; Idzerda, Y. U.; Arenholz, E.

    2008-06-24

    A large exchange splitting of the conduction band in ultrathin films of the ferromagnetic semiconductor EuO was determined quantitatively, by using EuO as a tunnel barrier and fitting the current-voltage characteristics and temperature dependence to tunneling theory. This exchange splitting leads to different tunnel barrier heights for spin-up and spin-down electrons, and is large enough to produce a near fully spin-polarized current. Moreover, the magnetic properties of these ultrathin films (<6 nm) show a reduction in Curie temperature with decreasing thickness, in agreement with theoretical calculation [R. Schiller et al., Phys. Rev. Lett. 86, 3847 (2001)].

  12. 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

    2012-01-01

    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

  13. Large amplitude oscillation of magnetization in spin-torque oscillator stabilized by field-like torque

    SciTech Connect (OSTI)

    Taniguchi, Tomohiro Kubota, Hitoshi; Imamura, Hiroshi; Tsunegi, Sumito

    2015-05-07

    Oscillation frequency of spin torque oscillator with a perpendicularly magnetized free layer and an in-plane magnetized pinned layer is theoretically investigated by taking into account the field-like torque. It is shown that the field-like torque plays an important role in finding the balance between the energy supplied by the spin torque and the dissipation due to the damping, which results in a steady precession. The validity of the developed theory is confirmed by performing numerical simulations based on the Landau-Lifshitz-Gilbert equation.

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

    SciTech Connect (OSTI)

    Tomasello, R.; Carpentieri, M.; Finocchio, G.

    2013-12-16

    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. 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

  16. Corrosion behavior of magnetic ferrite coating prepared by plasma spraying

    SciTech Connect (OSTI)

    Liu, Yi; Wei, Shicheng Tong, Hui; Tian, Haoliang; Liu, Ming; Xu, Binshi

    2014-12-15

    Graphical abstract: The saturation magnetization (M{sub s}) of the ferrite coating is 34.417 emu/g while the M{sub s} value of the ferrite powder is 71.916 emu/g. It can be seen that plasma spray process causes deterioration of the room temperature soft magnetic properties. - Highlights: • Spinel ferrite coatings have been prepared by plasma spraying. • The coating consists of nanocrystalline grains. • The saturation magnetization of the ferrite coating is 34.417 emu/g. • Corrosion behavior of the ferrite coating was examined in NaCl solution. - Abstract: In this study, spray dried spinel ferrite powders were deposited on the surface of mild steel substrate through plasma spraying. The structure and morphological studies on the ferrite coatings were carried out using X-ray diffraction, scanning electron microscope and Raman spectroscopy. It was showed that spray dried process was an effective method to prepare thermal spraying powders. The coating showed spinel structure with a second phase of LaFeO{sub 3}. The magnetic property of the ferrite samples were measured by vibrating sample magnetometer. The saturation magnetization (M{sub s}) of the ferrite coating was 34.417 emu/g. The corrosion behavior of coating samples was examined by electrochemical impedance spectroscopy. EIS diagrams showed three corrosion processes as the coating immersed in 3.5 wt.% NaCl solution. The results suggested that plasma spraying was a promising technology for the production of magnetic ferrite coatings.

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

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

    phenomenon which is found across a large range of length scales, from galaxies to hurricanes and even down to the nanoscale as in superconducting materials. Magnetic vortex...

  18. 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

    2015-07-09

    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.

  19. Coherent heteronuclear spin dynamics in an ultracold spin-1 mixture

    E-Print Network [OSTI]

    Li, Xiaoke; He, Xiaodong; Wang, Fudong; Guo, Mingyang; Xu, Zhi-Fang; Zhang, Shizhong; Wang, Dajun

    2015-01-01

    We report the observation of coherent heteronuclear spin dynamics driven by inter-species spin-spin interaction in an ultracold spinor mixture, which manifests as periodical and well correlated spin oscillations between two atomic species. In particular, we investigate the magnetic field dependence of the oscillations and find a resonance behavior which depends on {\\em both} the linear and quadratic Zeeman effects and the spin-dependent interaction. We also demonstrate a unique knob for controlling the spin dynamics in the spinor mixture with species-dependent vector light shifts. Our finds are in agreement with theoretical simulations without any fitting parameters.

  20. Adsorption-induced magnetic properties and metallic behavior of graphene

    SciTech Connect (OSTI)

    Zhou, Yungang; Zu, Xiaotao T.; Gao, Fei; Lv, H. F.; Xiao, Haiyan J.

    2009-09-21

    Magnetic properties and electronic structures of graphene with Cl, S, and P adsorption have been investigated using ab initio calculations. The adsorption of Cl leads to Fermi level shifting to valence band, which results in metallic graphene. A band gap of 0.6 eV emerges in a S-absorbed graphene, leading to the semiconducting graphene. The unpaired electrons in the absorbed P atom is polarized and thus, exhibits a magnetic moment of 0.86 ?B, while no magnetic moment has been observed after Cl and S adsorption. This demonstrates that the magnetic properties and conductive behavior of graphene can be modified via atom adsorption. Specially, P-absorbed graphene may be useful for spintronic applications, such as tunneling magnetoresistance.

  1. Spin-dependent transport behavior in C{sub 60} and Alq{sub 3} based spin valves with a magnetite electrode (invited)

    SciTech Connect (OSTI)

    Zhang, Xianmin Mizukami, Shigemi; Ma, Qinli; Kubota, Takahide; Miyazaki, Terunobu; Oogane, Mikihiko; Naganuma, Hiroshi; Ando, Yasuo

    2014-05-07

    The spin-dependent transport behavior in organic semiconductors (OSs) is generally observed at low temperatures, which likely results from poor spin injection efficiency at room temperature from the ferromagnetic metal electrodes to the OS layer. Possible reasons for this are the low Curie temperature and/or the small spin polarization efficiency for the ferromagnetic electrodes used in these devices. Magnetite has potential as an advanced candidate for use as the electrode in spintronic devices, because it can achieve 100% spin polarization efficiency in theory, and has a high Curie temperature (850?K). Here, we fabricated two types of organic spin valves using magnetite as a high efficiency electrode. C{sub 60} and 8-hydroxyquinoline aluminum (Alq{sub 3}) were employed as the OS layers. Magnetoresistance ratios of around 8% and over 6% were obtained in C{sub 60} and Alq{sub 3}-based spin valves at room temperature, respectively, which are two of the highest magnetoresistance ratios in organic spin valves reported thus far. The magnetoresistance effect was systemically investigated by varying the thickness of the Alq{sub 3} layer. Moreover, the temperature dependence of the magnetoresistance ratios for C{sub 60} and Alq{sub 3}-based spin valves were evaluated to gain insight into the spin-dependent transport behavior. This study provides a useful method in designing organic spin devices operated at room temperature.

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

    SciTech Connect (OSTI)

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

    2014-01-28

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

  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. 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

    2008-09-01

    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

  5. Pulsed Gradient Spin Echo Nuclear Magnetic Resonance Imaging of Diffusion in Granular Flow

    SciTech Connect (OSTI)

    Seymour, Joseph D.; Caprihan, Arvind; Altobelli, Stephen A.; Fukushima, Eiichi

    2000-01-10

    We derive the formalism to obtain spatial distributions of collisional correlation times for macroscopic particles undergoing granular flow from pulsed gradient spin echo nuclear magnetic resonance diffusion data. This is demonstrated with an example of axial motion in the shear flow regime of a 3D granular flow in a horizontal rotating cylinder at one rotation rate. (c) 2000 The American Physical Society.

  6. Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic...

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

    on the Dynamic Behavior of Magnetic Vortices Print Soft magnetic, micron-sized thin-film structures with magnetic vortices are intriguing systems that may one day be used in...

  7. Mass and magnetic dipole moment of negative parity heavy baryons with spin--3/2

    E-Print Network [OSTI]

    Azizi, K

    2015-01-01

    We calculate the mass and residue of the heavy spin--3/2 negative parity baryons with single heavy bottom or charm quark by the help of a two-point correlation function. We use the obtained results to investigate the diagonal radiative transitions among the baryons under consideration. In particular, we compute corresponding transition form factors via light cone QCD sum rules which are then used to obtain the magnetic dipole moments of the heavy spin--3/2 negative parity baryons. We remove the pollutions coming from the positive parity spin--3/2 and positive/negative parity spin--1/2 baryons by constructing sum rules for different Lorentz structures. We compare the results obtained with the existing theoretical predictions.

  8. Mass and magnetic dipole moment of negative parity heavy baryons with spin--3/2

    E-Print Network [OSTI]

    K. Azizi; H. Sundu

    2015-06-28

    We calculate the mass and residue of the heavy spin--3/2 negative parity baryons with single heavy bottom or charm quark by the help of a two-point correlation function. We use the obtained results to investigate the diagonal radiative transitions among the baryons under consideration. In particular, we compute corresponding transition form factors via light cone QCD sum rules which are then used to obtain the magnetic dipole moments of the heavy spin--3/2 negative parity baryons. We remove the pollutions coming from the positive parity spin--3/2 and positive/negative parity spin--1/2 baryons by constructing sum rules for different Lorentz structures. We compare the results obtained with the existing theoretical predictions.

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

    SciTech Connect (OSTI)

    Mamone, Salvatore Concistrè, Maria; Carignani, Elisa; Meier, Benno; Krachmalnicoff, Andrea; Johannessen, Ole G.; Denning, Mark; Carravetta, Marina; Whitby, Richard J.; Levitt, Malcolm H.; Lei, Xuegong; Li, Yongjun; Goh, Kelvin; Horsewill, Anthony J.

    2014-05-21

    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.

  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.

    2009-02-09

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

    E-Print Network [OSTI]

    Nesterov, Konstantin N

    2015-01-01

    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.

  12. Torque Enhancement, Spin Equilibrium, and Jet Power from Disk-Induced Opening of Pulsar Magnetic Fields

    E-Print Network [OSTI]

    Parfrey, Kyle; Beloborodov, Andrei M

    2015-01-01

    The interaction of a rotating star's magnetic field with a surrounding plasma disk lies at the heart of many questions posed by neutron stars in X-ray binaries. We consider the opening of stellar magnetic flux due to differential rotation along field lines coupling the star and disk, using a simple model for the disk-opened flux, the torques exerted on the star by the magnetosphere, and the power extracted by the electromagnetic wind. We examine the conditions under which the system enters an equilibrium spin state, in which the accretion torque is instantaneously balanced by the pulsar wind torque alone. For magnetic moments, spin frequencies, and accretion rates relevant to accreting millisecond pulsars, the spin-down torque from this enhanced pulsar wind can be substantially larger than that predicted by existing models of the disk-magnetosphere interaction, and is in principle capable of maintaining spin equilibrium at frequencies less than 1 kHz. We speculate that this mechanism may account for the non-d...

  13. Spin-fluctuation mechanism of anomalous temperature dependence of magnetocrystalline anisotropy in itinerant magnets

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

    Zhuravlev, I. A.; Antropov, V. P.; Belashchenko, K. D.

    2015-11-16

    The origins of the anomalous temperature dependence of magnetocrystalline anisotropy in (Fe1–xCox)2B alloys are elucidated using first-principles calculations within the disordered local moment model. Excellent agreement with experimental data is obtained. The anomalies are associated with the changes in band occupations due to Stoner-like band shifts and with the selective suppression of spin-orbit “hot spots” by thermal spin fluctuations. Under certain conditions, the anisotropy can increase, rather than decrease, with decreasing magnetization. This peculiar electronic mechanisms is in stark contrast to the assumptions of the existing models.

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

    E-Print Network [OSTI]

    Tomislav Ivezic

    2010-03-23

    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.

  15. Spectra and magnetic properties of large spins in external fields 

    E-Print Network [OSTI]

    Kalatsky, V. A.; Pokrovsky, Valery L.

    1999-01-01

    quantization rule: R Jz~f ,E !df5~n1gB!p , ~2! where Jz(f ,E) can be found from the equation f (J)5E with the substitution Jx5AJ22Jz2 cos f, Jy5AJ22Jz2 sin f, and gB is a constant. Let us first consider general properties of spin trajectories in zero... with the smallest ci j 5c , and neglect tunneling between more remote states with ci j.c . To estimate the value of c, we need to specify the Hamiltonian. For simplicity we consider the case of the cu- bic symmetry with the Hamiltonian H 1O52a~Jx41Jy41Jz4!, ~3...

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

    E-Print Network [OSTI]

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

    1995-06-09

    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.

  17. 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)

    2010-09-01

    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.

  18. Angular dependence of the spin textures in two-dimensional chiral magnets

    SciTech Connect (OSTI)

    Tang, Dan; Qi, Yang

    2015-05-28

    The angular dependence of spin textures in thin helimagnetic films is investigated by a Monte Carlo simulation. When an external field is applied at an angle relative to the film normal, we find that the skyrmion states with broken axis-symmetric structure are able to persist over a wide range of angles by changing the spin orientation. In addition, the uniaxial anisotropy is able to stabilize the distorted skyrmions. This behavior reflects the robust topological stability of skyrmion states in helimagnets and favors their application in spintronic devices.

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

    E-Print Network [OSTI]

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

    2007-01-01

    concepts such as spintronics, where in addition to theLogical elements for spintronics, non-volatile magnetic

  20. Quantum decoherence of spin states in an electric-field controllable single molecular magnet

    E-Print Network [OSTI]

    Xiang Hao; Chen Liu; Shiqun Zhu

    2012-08-08

    The time evolution of low energy spin states of a single molecular magnet in a local electric field is investigated. The decoherence of the driven single molecular magnet weakly coupled to a thermal bosonic environment is analyzed by the second-order time-convolutionless non-Markovian master equation. If the characteristic time of the system is much smaller than the correlation time of the environment, the analytical expression of the reduced density matrix of the system is obtained. The non-Markovian dynamics of the spin states at low temperatures is induced by the memory effects in the decay rates. The non-Markovian oscillation of the Bloch vector is presented. The quantum decoherence can be effectively restrained with the help of the reasonable manipulation of the environment spectral density function and local electric field. The influence of the dissipation on the pointer states are investigated by the von Neumann entropy. The pointer states can be selected by the environment.

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

    E-Print Network [OSTI]

    Alexander J. Silenko

    2007-10-02

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

  2. Functional integral over velocities for a spinning particle with and without anomalous magnetic moment in a constant electromagnetic field

    E-Print Network [OSTI]

    Wellington da Cruz

    1997-10-16

    The technique of functional integration over velocities is applied to the calculation of the propagator of a spinning particle with and without anomalous magnetic moment. A representation for the spin factor is obtained in this context for the particle in a constant electromagnetic field. As a by-product, we also obtain a Schwinger representation for the first case.

  3. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy

    E-Print Network [OSTI]

    Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic (2014) Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin

  4. Magnetic ordering in tetragonal FeS: Evidence for strong itinerant spin fluctuations

    SciTech Connect (OSTI)

    Kwon, K.D.; Refson, K.; Bone, S.; Qiao, R.; Yang, W.; Liu, Z.; Sposito, G.

    2010-11-01

    Mackinawite is a naturally occurring layer-type FeS mineral important in biogeochemical cycles and, more recently, in the development of microbial fuel cells. Conflicting results have been published as to the magnetic properties of this mineral, with Moessbauer spectroscopy indicating no magnetic ordering down to 4.2 K but density functional theory (DFT) predicting an antiferromagnetic ground state, similar to the Fe-based high-temperature superconductors with which it is isostructural and for which it is known that magnetism is suppressed by strong itinerant spin fluctuations. We investigated this latter possibility for mackinawite using photoemission spectroscopy, near-edge x-ray absorption fine structure spectroscopy, and DFT computations. Our Fe 3{sub s} core-level photoemission spectrum of mackinawite showed a clear exchange-energy splitting (2.9 eV) consistent with a 1 {micro}{sub B} magnetic moment on the Fe ions, while the Fe L-edge x-ray absorption spectrum indicated rather delocalized Fe 3{sub d} electrons in mackinawite similar to those in Fe metal. Our DFT computations demonstrated that the ground state of mackinawite is single-stripe antiferromagnetic, with an Fe magnetic moment (2.7 {micro}{sub B}) that is significantly larger than the experimental estimate and has a strong dependence on the S height and lattice parameters. All of these trends signal the existence of strong itinerant spin fluctuations. If spin fluctuations prove to be mediators of electron pairing, we conjecture that mackinawite may be one of the simplest Fe-based superconductors.

  5. Magnetic Graphene Nanohole Superlattices

    E-Print Network [OSTI]

    Yu, Decai; Liu, Miao; Liu, Wei; Liu, Feng

    2008-01-01

    We investigate the magnetic properties of nano-holes (NHs) patterned in graphene using first principles calculations. We show that superlattices consisting of a periodic array of NHs form a new family of 2D crystalline "bulk" magnets whose collective magnetic behavior is governed by inter-NH spin-spin interaction. They exhibit long-range magnetic order well above room temperature. Furthermore, magnetic semiconductors can be made by doping magnetic NHs into semiconducting NH superlattices. Our findings offer a new material system for fundamental studies of spin-spin interaction and magnetic ordering in low dimensions, and open up the exciting opportunities of making engineered magnetic materials for storage media and spintronics applications.

  6. Magnetic Transitions in the Spin-5/2 Frustrated Magnet BiMn2PO6 and Strong Lattice Softening in BiMn2PO6 and BiZn2PO6 Below 200 K

    SciTech Connect (OSTI)

    Nath, R; Ranjith, K M; Roy, B; Johnston, D C; Furukawa, Y; Tsirlin, A A

    2014-07-01

    The crystallographic, magnetic, and thermal properties of polycrystalline BiMn2PO6 and its nonmagnetic analog BiZn2PO6 are investigated by x-ray diffraction, magnetization M, magnetic susceptibility ?, heat capacity Cp, and P31 nuclear magnetic resonance (NMR) measurements versus applied magnetic field H and temperature T as well as by density-functional band theory and molecular-field calculations. Both compounds show a strong monotonic lattice softening on cooling, where the Debye temperature decreases by a factor of two from ?D?650 K at T=300 K to ?D?300 K at T=2 K. The ?(T) data for BiMn2PO6 above 150 K follow a Curie-Weiss law with a Curie constant consistent with a Mn+2 spin S=5/2 with g factor g=2 and an antiferromagnetic (AFM) Weiss temperature ?CW??78 K. The ? data indicate long-range AFM ordering below TN?30 K, confirmed by a sharp ?-shaped peak in Cp(T) at 28.8 K. The magnetic entropy at 100 K extracted from the Cp(T) data is consistent with spin S=5/2 for the Mn+2 cations. The band-theory calculations indicate that BiMn2PO6 is an AFM compound with dominant interactions J1/kB?6.7 K and J3/kB?5.6 K along the legs and rungs of a Mn two-leg spin-ladder, respectively. However, sizable and partially frustrating interladder couplings lead to an anisotropic three-dimensional magnetic behavior with long-range AFM ordering at TN?30 K observed in the ?, Cp, and NMR measurements. A second magnetic transition at ?10 K is observed from the ? and NMR measurements but is not evident in the Cp data. The Cp data at low T suggest a significant contribution from AFM spin waves moving in three dimensions and the absence of a spin-wave gap. A detailed analysis of the NMR spectra indicates commensurate magnetic order between 10 and 30 K, while below 10 K additional features appear that may arise from an incommensurate modulation and/or spin canting. The commensurate order is consistent with microscopic density functional calculations that yield a collinear Néel-type AFM spin arrangement both within and between the ladders, despite the presence of multiple weak interactions frustrating this magnetic structure of the Mn spins. Frustration for AFM ordering and the one-dimensional spatial anisotropy of the three-dimensional spin interactions are manifested in the frustration ratio f=|?CW|/TN?2.6, indicating a suppression of TN from 68 K in the absence of these effects to the observed value of about 30 K in BiMn2PO6.

  7. Spin-lozenge thermodynamics and magnetic excitations in Na3RuO4

    SciTech Connect (OSTI)

    Haraldsen, Jason T; Stone, Matthew B; Lumsden, Mark D; Barnes, Ted {F E }; Jin, Rongying; Taylor, J. W.; Fernandez-Alonso, F

    2009-01-01

    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.

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

    SciTech Connect (OSTI)

    Tamaru, S. Kubota, H.; Yakushiji, K.; Konoto, M.; Nozaki, T.; Fukushima, A.; Imamura, H.; Taniguchi, T.; Arai, H.; Tsunegi, S.; Yuasa, S.; Suzuki, Y.

    2014-05-07

    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.

  9. Magnetization and 13C NMR spin-lattice relaxation of nanodiamond powder

    SciTech Connect (OSTI)

    Levin, E.M.; Fang, X.W.; Bud'ko, S.L.; Straszheim, W.E.; McCallum, R.W.; Schmidt-Rohr, K.

    2008-02-15

    The bulk magnetization at temperatures of 1.8-400 K and in magnetic fields up to 70 kOe, the ambient temperature {sup 13}C NMR spin-lattice relaxation, T{sub 1,c}, and the elemental composition of three nanodiamond powder samples have been studied. The total magnetization of nanodiamond can be explained in terms of contributions from (1) the diamagnetic effect of carbon, (2) the paramagnetic effect of unpaired electrons present in nanodiamond grains, and (3) ferromagnetic-like and (4) superparamagnetic contributions from Fe-containing particles detected in spatially resolved energy-dispersive spectroscopy. Contributions (1) and (2) are intrinsic to nanodiamond, while contributions (3) and (4) arise from impurities naturally present in detonation nanodiamond samples. {sup 13}C NMR T{sub 1,c} relaxation would be unaffected by the presence of the ferromagnetic particles with the bulk magnetization of {approx} 0.01 emu/g at 300 K. Thus, a reduction of T{sub 1,c} by 3 orders of magnitude compared to natural and synthetic microdiamonds confirms the presence of unpaired electrons in the nanodiamond grains. The spin concentration in nanodiamond powder corresponds to {approx}30 unpaired electrons per {approx}4.6 nm diameter nanodiamond grain.

  10. 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)

    2014-09-15

    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.

  11. -Supplementary Material -Electrical read-out of individual nuclear spin trajectories in a single-molecule magnet

    E-Print Network [OSTI]

    . Terbium Double-Decker 1 S3. Nuclear Spin Read-Out 2 S4. Quantum Tunnelling of Magnetization 3 S5. Quantum magnetic field sweeps in three dimensions at field sweep rates up to 0.2 T/s. S2. TERBIUM DOUBLE-DECKER We

  12. Magnetization stability analysis of the Stoner-Wohlfarth model under a spin-polarized current with a tilted polarization

    SciTech Connect (OSTI)

    Wang, Zhiyuan; Sun, Z. Z.

    2014-02-14

    The stationary-state solutions of magnetization dynamics under a spin-polarized current that was polarized in an arbitrary direction were investigated by solving the Landau-Lifshitz-Gilbert-Slonczewski equation for a single-domain magnet. Taking into consideration the uniaxial magnetic anisotropy, the equilibrium directions of the magnetization vectors were analytically obtained by solving an algebraic cubic equation. It was found that one to three pairs of magnetization equilibrium states existed, depending on the current intensity and the direction of the spin polarization. By numerically analyzing the stabilities of these equilibrium states, the threshold switching current for the reversing the magnetic vector was obtained under different current polarization configurations, which may be useful for use in future spintronics devices.

  13. Switching Magnetization of a Nanoscale Ferromagnetic Particle Using Nonlocal Spin Injection T. Kimura,1,2,3,* Y. Otani,1,2,3

    E-Print Network [OSTI]

    Otani, Yoshichika

    to operate future spintronic devices including a magnetic random access memory [1]. Unlike conventional technologies for developing spintronic devices. The switching mechanism due to spin torque is explained

  14. 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)

    1999-10-01

    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}

  15. Propagator of a Charged Particle with a Spin in Uniform Magnetic and Perpendicular Electric Fields

    E-Print Network [OSTI]

    Ricardo Cordero-Soto; Raquel M. Lopez; Erwin Suazo; Sergei K. Suslov

    2008-02-05

    We construct an explicit solution of the Cauchy initial value problem for the time-dependent Schroedinger equation for a charged particle with a spin moving in a uniform magnetic field and a perpendicular electric field varying with time. The corresponding Green function (propagator) is given in terms of elementary functions and certain integrals of the fields with a characteristic function, which should be found as an analytic or numerical solution of the equation of motion for the classical oscillator with a time-dependent frequency. We discuss a particular solution of a related nonlinear Schroedinger equation and some special and limiting cases are outlined.

  16. Nuclear magnetic relaxation of a three spin asymmetric molecule in a liquid 

    E-Print Network [OSTI]

    Kattawar, George Williford

    1961-01-01

    is the quaternion ~ ( o(/~) + g ~ Q &/2) &Z) The quantity C is a unit vector in the direction of the axis of the rotation, having components 19 C, =~a'C d', C, = ~s ~~ ~ &~=~+. A quaternion can be considered to be the sum of a scalar and a vector, (a + bC... for the degree of MASTER OF SCIENCE August 1961 Major Sub)ect: Physics NUCLEAR MAGNETIC RELAXATION OF A THREE SPIN ASYMMETRIC MOLECULE IN A LIQUID A Thesis By George W. Kattawar Approved as to style and content by: ), , i, ? a rman o Comm ttee g-C e...

  17. 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)

    2014-05-07

    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.

  18. Solid state Stern-Gerlach spin-splitter for magnetic field sensoring, spintronics, and quantum computing

    E-Print Network [OSTI]

    Kristofer Björnson; Annica M. Black-Schaffer

    2015-09-17

    We show that the edge of a two-dimensional topological insulator can be used to construct a solid state Stern-Gerlach spin-splitter. By threading such a Stern-Gerlach apparatus with a magnetic flux, Ahranov-Bohm like interference effects are introduced. Using ferromagnetic leads, the setup can be used to both measure magnetic flux and as a spintronics switch. With normal metallic leads a switchable spintronics NOT-gate can be implemented. Furthermore, we show that a sequence of such devices can be used to construct a single-qubit $SU(2)$-gate, one of the two gates required for a universal quantum computer. The field sensitivity, or switching field, $b$ is related to the device characteristic size $r$ through $b = \\frac{\\hbar}{qr^2}$, with $q$ the unit of electric charge.

  19. Quantum field theory treatment of magnetic effects on the spin and orbital angular momentum of a free electron

    E-Print Network [OSTI]

    P. Kurian; C. Verzegnassi

    2015-08-01

    We consider in a quantum field theory framework the effects of a classical magnetic field on the spin and orbital angular momentum (OAM) of a free electron. We derive formulae for the changes in the spin and OAM due to the introduction of a general classical background field. We consider then a constant magnetic field, in which case the relevant expressions of the effects become much simpler and conversions between spin and OAM become readily apparent. An estimate of the expectation values for a realistic electron state is also given. Our findings may be of interest to researchers in spintronics and the field of quantum biology, where electron spin has been implicated on macroscopic time and energy scales.

  20. 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.

    2008-01-01

    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.

  1. LETTER Earth Planets Space, 55, 153157, 2003 Asymmetric behavior of magnetic dip poles

    E-Print Network [OSTI]

    Dormy, Emmanuel

    LETTER Earth Planets Space, 55, 153­157, 2003 Asymmetric behavior of magnetic dip poles M. Mandea (Received November 8, 2002; Revised February 3, 2003; Accepted March 3, 2003) The north magnetic dip pole the dipolar field as a whole, but only the north magnetic pole. We demonstrate how this rapid displacement

  2. 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.

    2006-01-24

    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.

  3. Accelerated 2D magnetic resonance spectroscopy of single spins using matrix completion

    E-Print Network [OSTI]

    Jochen Scheuer; Alexander Stark; Matthias Kost; Martin B. Plenio; Boris Naydenov; Fedor Jelezko

    2015-07-14

    Two dimensional nuclear magnetic resonance (NMR) spectroscopy is one of the major tools for analysing the chemical structure of organic molecules and proteins. Despite its power, this technique requires long measurement times, which, particularly in the recently emerging diamond based single molecule NMR, limits its application to stable samples. Here we demonstrate a method which allows to obtain the spectrum by collecting only a small fraction of the experimental data. Our method is based on matrix completion which can recover the full spectral information from randomly sampled data points. We confirm experimentally the applicability of this technique by performing two dimensional electron spin echo envelope modulation (ESEEM) experiments on a two spin system consisting of a single nitrogen vacancy (NV) centre in diamond coupled to a single 13C nuclear spin. We show that the main peaks in the spectrum can be obtained with only 10 % of the total number of the data points. We believe that our results reported here can find an application in all types of two dimensional spectroscopy, as long as the measured matrices have a low rank.

  4. Spins and magnetic moments of 58;60;62;64Mn ground states and isomers

    E-Print Network [OSTI]

    H. Heylen; C. Babcock; J. Billowes; M. L. Bissell; K. Blaum; P. Campbell; B. Cheal; R. F. Garcia Ruiz; Ch. Geppert; W. Gins; M. Kowalska; K. Kreim; S. M. Lenzi; I. D. Moore; R. Neugart; G. Neyens; W. Nörtershäuser; J. Papuga; D. T. Yordanov

    2015-08-25

    The odd-odd 54;56;58;60;62;64Mn isotopes (Z = 25) were studied using bunched-beam collinear laser spectroscopy at ISOLDE, CERN. From the measured hyperfine spectra the spins and magnetic moments of Mn isotopes up to N = 39 were extracted. The previous tentative ground state spin assignments of 58;60;62;64Mn are now firmly determined to be I = 1 along with an I = 4 assignment for the isomeric states in 58;60;62Mn. The I = 1 magnetic moments show a decreasing trend with increasing neutron number while the I = 4 moments remain quite constant between N = 33 and N = 37. The results are compared to large-scale shell-model calculations using the GXPF1A and LNPS effective interactions. The excellent agreement of the ground state moments with the predictions from the LNPS calculations illustrates the need for an increasing amount of proton excitations across Z = 28 and neutron excitations across N = 40 in the ground state wave functions from N = 37 onwards.

  5. Spins and magnetic moments of 58;60;62;64Mn ground states and isomers

    E-Print Network [OSTI]

    Heylen, H; Billowes, J; Bissell, M L; Blaum, K; Campbell, P; Cheal, B; Ruiz, R F Garcia; Geppert, Ch; Gins, W; Kowalska, M; Kreim, K; Lenzi, S M; Moore, I D; Neugart, R; Neyens, G; Nörtershäuser, W; Papuga, J; Yordanov, D T

    2015-01-01

    The odd-odd 54;56;58;60;62;64Mn isotopes (Z = 25) were studied using bunched-beam collinear laser spectroscopy at ISOLDE, CERN. From the measured hyperfine spectra the spins and magnetic moments of Mn isotopes up to N = 39 were extracted. The previous tentative ground state spin assignments of 58;60;62;64Mn are now firmly determined to be I = 1 along with an I = 4 assignment for the isomeric states in 58;60;62Mn. The I = 1 magnetic moments show a decreasing trend with increasing neutron number while the I = 4 moments remain quite constant between N = 33 and N = 37. The results are compared to large-scale shell-model calculations using the GXPF1A and LNPS effective interactions. The excellent agreement of the ground state moments with the predictions from the LNPS calculations illustrates the need for an increasing amount of proton excitations across Z = 28 and neutron excitations across N = 40 in the ground state wave functions from N = 37 onwards.

  6. 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. Manju, M. R. Dayal, Vijaylakshmi

    2014-04-24

    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.

  7. U-spin predictions of the transition magnetic moments of the electromagnetic decay of the {Sigma}{sup ?}(1385) baryons

    SciTech Connect (OSTI)

    Keller, Dustin M. [University of Virginia; Hicks, Kenneth H. [OHIO

    2013-05-01

    The transition magnetic moments for decuplet-to-octet baryon electromagnetic decays are calculated from the CLAS experimental results and are compared with calculations to first order in the 1/N{sub c} expansion of quantum chromodynamics (QCD) and new U-spin predictions. Using the U-spin predictions for the {Sigma} *{sup 0} --> {Sigma}{sup 0} {gamma} and {Sigma} *{sup +} ? {Sigma}{sup +} {gamma} decays, the SU(3)-forbidden transition {Sigma} *{sup -} ? {Sigma}{sup -} {gamma} is obtained. In addition, the doubly strange baryon radiative decay {Xi} *{sup 0} ? {Xi} {gamma} is predicted using U-spin.

  8. Spin-lattice relaxation within a dimerized Ising chain in a magnetic field

    SciTech Connect (OSTI)

    Erdem, R?za E-mail: rerdem29@hotmail.com; Gülp?nar, Gül; Yalç?n, Orhan; Pawlak, Andrzej

    2014-07-21

    A qualitative study of the spin-lattice relaxation within a dimerized Ising chain in a magnetic field is presented. We have first determined the time dependence of the deviation of the lattice distortion parameter ?? from the equilibrium state within framework of a technique combining the statistical equilibrium theory based on the transfer matrix method and the linear theory of irreversible thermodynamics. We have shown that the time dependence of the lattice distortion parameter is characterized by a single time constant (?) which diverges around the critical point in both dimerized (??0) and uniform (?=0) phase regions. When the temperature and magnetic field are fixed to certain values, the time ? depends only on exchange coupling between the spins. It is a characteristic time associated with the long wavelength fluctuations of distortion. We have also taken into account the effects of spatial fluctuations on the relaxation time using the full Landau-Ginzburg free energy functional. We have found an explicit expression for the relaxation time as a function of temperature, coupling constant and wave vector (q) and shown that the critical mode corresponds to the case q=0. Finally, our results are found to be in good qualitative agreement with the results obtained in recent experimental study on synchrotron x-ray scattering and muon spin relaxation in diluted material Cu{sub 1?y}Mg{sub y}GeO{sub 3} where the composition y is very close to 0.0209. These results can be considered as natural extensions of some previous works on static aspects of the problem.

  9. Goos-Hänchen effect and bending of spin wave beams in thin magnetic films

    SciTech Connect (OSTI)

    Gruszecki, P. Krawczyk, M.; Romero-Vivas, J.; Dadoenkova, Yu. S.; Dadoenkova, N. N.; Lyubchanskii, I. L.

    2014-12-15

    For magnon spintronic applications, the detailed knowledge of spin wave (SW) beam dispersion, transmission (reflection) of SWs passing through (reflected from) interfaces, or borders or the scattering of SWs by inhomogeneities is crucial. These wave properties are decisive factors on the usefulness of a particular device. Here, we demonstrate, using micromagnetic simulations supported by an analytical model, that the Goos-Hänchen (GH) shift exists for SW reflecting from thin film edge and that with the effect becomes observable. We show that this effect will exist for a broad range of frequencies in the dipole-exchange range, with the magnetization degree of pinning at the film edge as the crucial parameter, whatever its nature. Moreover, we have also found that the GH effect can be accompanied or even dominating by a bending of the SW beam due to the inhomogeneity of the internal magnetic field. This inhomogeneity, created by demagnetizing field taking place at the film edge, causes gradual change of SWs refractive index. The refraction of the SW beams by the non-uniformity of the magnetic field enables the exploration of graded index magnonics and metamaterial properties for the transmission and processing of information at nanoscale.

  10. 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)

    2014-03-05

    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.

  11. Pseudo-hermitian interaction between an oscillator and a spin half particle in the external magnetic field

    E-Print Network [OSTI]

    Bhabani Prasad Mandal

    2004-12-15

    We consider a spin half particle in the external magnetic field which couples to a harmonic oscillator through some pseudo-hermitian interaction. We find that the energy eigenvalues for this system are real even though the interaction is not PT invariant.

  12. 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

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

    SciTech Connect (OSTI)

    Ma, L.; Fan, W. J. Chen, F. L.; Zhou, S. M.; Li, S. F.; Lai, T. S.; He, P.; Xu, X. G.; Jiang, Y.

    2014-09-21

    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.

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

    SciTech Connect (OSTI)

    Evangelisti, Marco; Sorop, Tibi G; Bakharev, Oleg N; Visser, Dirk; Hillier, Adrian D.; Alonso, Juan; Haase, Markus; Boatner, Lynn A; De Jongh, L. Jos

    2011-01-01

    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.

  15. 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.; Blundell, S. J.; Lancaster, T.; Good, J.; Mitchell, R.; Owczarkowski, M.; Poli, S.; Scheuermann, R.; Salman, Z.

    2011-07-15

    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.

  16. Multifrequency spin resonance in diamond

    SciTech Connect (OSTI)

    Childress, Lilian; McIntyre, Jean

    2010-09-15

    Magnetic resonance techniques provide a powerful tool for controlling spin systems, with applications ranging from quantum information processing to medical imaging. Nevertheless, the behavior of a spin system under strong excitation remains a rich dynamical problem. In this paper, we examine spin resonance of the nitrogen-vacancy center in diamond under conditions outside the regime where the usual rotating-wave approximation applies, focusing on effects of multifrequency excitation and excitation with orientation parallel to the spin quantization axis. Strong-field phenomena such as multiphoton transitions and coherent destruction of tunneling are observed in the spectra and analyzed via numerical and analytic theory. In addition to illustrating the response of a spin system to strong multifrequency excitation, these observations may inform techniques for manipulating electron-nuclear spin quantum registers.

  17. Current Controller with Defined Dynamic Behavior for an Interior Permanent Magnet

    E-Print Network [OSTI]

    Noé, Reinhold

    Current Controller with Defined Dynamic Behavior for an Interior Permanent Magnet Synchronous Motor combustion vehicles already provide. Today's modern HEV and EV mostly include interior permanent magnet]. The required torque, which is the reference variable for these applications, is generated by choosing

  18. 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)

    2010-10-15

    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.

  19. Nano-fabricated perpendicular magnetic anisotropy electrodes for lateral spin valves and observation of Nernst-Ettingshausen related signals

    SciTech Connect (OSTI)

    Chejanovsky, N.; Sharoni, A.

    2014-08-21

    Lateral spin valves (LSVs) are efficient structures for characterizing spin currents in spintronics devices. Most LSVs are based on ferromagnetic (FM) electrodes for spin-injection and detection. While there are advantages for using perpendicular magnetic anisotropy (PMA) FM, e.g., stability to nano-scaling, these have almost not been studied. This is mainly due to difficulties in fabricating PMA FMs in a lateral geometry. We present here an efficient method, based on ion-milling through an AlN mask, for fabrication of LSVs with multi-layered PMA FMs such as Co/Pd and Co/Ni. We demonstrate, using standard permalloy FMs, that the method enables efficient spin injection. We show the multi-layer electrodes retain their PMA properties as well as spin injection and detection in PMA LSVs. In addition, we find a large asymmetric voltage signal which increases with current. We attribute this to a Nernst-Ettingshausen effect caused by local Joule heating and the perpendicular magnetic easy axis.

  20. 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.

    2014-01-06

    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.

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

    E-Print Network [OSTI]

    Schelter, Eric John

    2005-08-29

    Clusters of metal ions that possess large numbers of magnetically coupled unpaired electrons have attracted much interest in recent years due to their fascinating magnetic behavior. With an appreciable component of magnetic anisotropy, these large...

  2. Spin-polarized semiconductor induced by magnetic impurities in graphene Maria Daghofer,1,2,3,* Nan Zheng,1,2,4 and Adriana Moreo1,2

    E-Print Network [OSTI]

    Tennessee, University of

    Spin-polarized semiconductor induced by magnetic impurities in graphene Maria Daghofer,1,2,3,* Nan; published 10 September 2010 The effective magnetic coupling between magnetic impurities adsorbed on graphene, which is mediated by the itinerant graphene electrons, and its impact on the electrons' spectral density

  3. Neutron scattering and thermodynamic studies of quantum magnetism on the kagomé lattice

    E-Print Network [OSTI]

    Chisnell, Robin Michael Daub

    2014-01-01

    The geometry of the kagome lattice leads to exciting novel magnetic behavior in both ferromagnetic and antiferromagnetic systems. The collective spin dynamics were investigated in a variety of magnetic materials featuring ...

  4. 2210 IEEE TRANSACTIONS ON MAGNETICS, VOL. 37, NO. 4, JULY 2001 Synthesis, Structural Order and Magnetic Behavior of

    E-Print Network [OSTI]

    Krishnan, Kannan M.

    of the nanocrystals were controlled by varying the surfactant, its concentration, the reaction rate and the reaction into ordered arrays and their magnetic behavior as a function of structural order (ferrofluids and 2D temperature. The Co particles are defect-free single crystals with a complex cubic structure related

  5. Thermal fluctuations and critical behavior in a magnetized, anisotropic plasma

    SciTech Connect (OSTI)

    Hazeltine, R. D.; Mahajan, S. M. [Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)] [Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)

    2013-12-15

    Thermal fluctuations in a magnetized, anisotropic plasma are studied by applying standard methods, based on the Einstein rule, to the known thermodynamic potential of the system. It is found in particular that magnetic fluctuations become critical when the anisotropy p{sub ?}?p{sub ?} changes sign. By examining the critical region, additional insight on the equations of state for near-critical anisotropic plasma is obtained.

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

    SciTech Connect (OSTI)

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

    2014-01-13

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

  7. 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

    2014-05-13

    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.

  8. Measurements accounting for the impediment of ion spin-up in rotating magnetic field driven field reversed configurations

    SciTech Connect (OSTI)

    Deards, C. L. [Lockheed Martin, 1011 Lockheed Way, Palmdale, California 93599 (United States); Hoffman, A. L.; Steinhauer, L. C. [Redmond Plasma Physics Laboratory, University of Washington, 14700 NE 95th Street, Suite 100, Redmond, Washington 98052 (United States)

    2011-11-15

    Improved vacuum hygiene, wall conditioning, and reduced recycling in the rotating magnetic field (RMF) driven translation, confinement, and sustainment-upgrade (TCSU) field reversed configuration experiment have made possible a more accurate assessment of the forces affecting ion spin-up. This issue is critical in plasmas sustained by RMFs, such as TCSU since ion spin-up can substantially reduce or cancel the RMF current drive effect. Several diagnostics are brought to bear, including a 3-axis translatable magnetic probe allowing the first experimental measurement of the end shorting effect. These results show that the ion rotation is determined by a balance between electron-ion friction, the end shorting effect, and ion drag against neutrals.

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

    SciTech Connect (OSTI)

    Blake, G.R.; Chapon, L.C.; Radaelli, P.G.; Park, S.; Hur, N.; Cheong, S-W.; Rodriguez-Carvajal, J.

    2005-06-01

    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.

  10. 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

    2014-12-23

    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.

  11. Hyperfine-induced hysteretic funnel structure in spin blockaded tunneling current of coupled vertical quantum dots at low magnetic field

    SciTech Connect (OSTI)

    Leary, A.; Wicha, A.; Harack, B.; Coish, W. A.; Hilke, M.; Yu, G.; Gupta, J. A.; Payette, C.; Austing, D. G.

    2013-12-04

    We outline the properties of the hyperfine-induced funnel structure observed in the two-electron spin blockade region of a weakly coupled vertical double quantum dot device. Hysteretic steps in the leakage current occur due to dynamic nuclear polarization when either the bias voltage or the magnetic field is swept up and down. When the bias voltage is swept, an intriguing ?3 mT wide cusp near 0 T appears in the down-sweep position, and when the magnetic field is swept, the current at 0 T can be switched from 'low' to 'high' as the bias is increased.

  12. GIAO-DFT Isotropic magnetic shielding constants and spin-spin coupling of tartaric acid in water solution

    E-Print Network [OSTI]

    Fideles, Bruna; Colherinhas, Guilherme

    2015-01-01

    We investigate the nuclear isotropic shielding constants and spin-spin coupling for oxygen and carbons atoms of isomers of tartaric acid in gas phase and water solutions by Monte Carlo simulation and quantum mechanics calculations using the GIAO-B3LYP approach. Solute polarization effects are included iteratively and play an important role in the quantitative determination of shielding constants. Our MP2/aug-cc-pVTZ results show substantial increases of the dipole moment in solution as compared with the gas phase results (61-221%). The solvent effects on the {\\sigma}(13C) [J(C-C)] values are in general small. More appreciable solvent effects can be seen on the {\\sigma}(17O) and J(C-O).

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

    SciTech Connect (OSTI)

    Garcial-Barriocanal, J; Cezar, J. C.; Bruno, F. Y.; Thakur, P.; Brookes, N. B.; Utfeld, C.; Riviera-Calzada, A.; Giblin, S. R.; Taylor, J. W.; Duffy, J. A.; Dugdale, S. B.; Nakamura, T.; Kodama, K.; Leon, C.; Okamoto, Satoshi; Santamaria, J.

    2010-01-01

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

  14. Transient and quasisteady behavior with rotating magnetic field current drive

    E-Print Network [OSTI]

    Washington at Seattle, University of

    rotamaks and the Star Thrust Experiment. Other sources of ion momentum are essential for RMF current drive in hotter, fusion-relevant plasmas. The properties of the quasisteady state are found, including the self that penetrate the plasma are a promising method by which to drive a steady current in magnetic fusion systems

  15. Scaling behavior of domain walls at the T =0 ferromagnet to spin-glass transition

    E-Print Network [OSTI]

    Peinke, Joachim

    ) Disordered model systems, governed by Edwards-Anderson Hamiltonian for Ising spins i =±1: H() = - i,j Jijij Quenched disorder: Jij > 0 : Jij -J2 /2 / 2 + (J -1) =0: SG with Gaussian disorder =1: Ferromagnet Ground states (GSs) Spin

  16. 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.

    2011-04-01

    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.

  17. Spin glass and semiconducting behavior in one-dimensional BaFe2-dSe3 (d~2) crystals

    SciTech Connect (OSTI)

    Saparov, Bayrammurad I [ORNL; Calder, Stuart A [ORNL; Sipos, Balazs [ORNL; Cao, Huibo [ORNL; Chi, Songxue [ORNL; Singh, David J [ORNL; Christianson, Andrew D [ORNL; Lumsden, Mark D [ORNL; Sefat, A. S. [Oak Ridge National Laboratory (ORNL)

    2011-01-01

    We investigate the physical properties and electronic structure of BaFe{sub 1.79(2)}Se{sub 3} crystals, which were grown out of tellurium flux. The crystal structure of the compound, an iron-deficient derivative of the ThCr{sub 2}Si{sub 2}-type, is built upon edge-shared FeSe{sub 4} tetrahedra fused into double chains. The semiconducting BaFe{sub 1.79(2)}Se{sub 3} ({rho}{sub 295K} = 0.18 {Omega} {center_dot} cm and E{sub g} = 0.30 eV) does not order magnetically; however, there is evidence for short-range magnetic correlations of spin glass type (T{sub f} {approx} 50 K) in magnetization, heat capacity, and neutron diffraction results. A one-third substitution of selenium with sulfur leads to a slightly higher electrical conductivity ({rho}{sub 295K } = 0.11 {Omega} {center_dot} cm and E{sub g} = 0.22 eV) and a lower spin glass freezing temperature (T{sub f} {approx} 15 K), corroborating with higher electrical conductivity reported for BaFe{sub 2}S{sub 3}. According to the electronic structure calculations, BaFe{sub 2}Se{sub 3} can be considered as a one-dimensional ladder structure with a weak interchain coupling.

  18. 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)

    2014-07-14

    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.

  19. Magnetic and dielectric behavior in YMn{sub 1?x}Fe{sub x}O{sub 3} (x???0.5)

    SciTech Connect (OSTI)

    Sharma, Neetika; Das, A. Mishra, S. K.; Meena, S. S.; Prajapat, C. L.; Singh, M. R.

    2014-06-07

    The role of doping Fe on the structural, magnetic, and dielectric properties of frustrated antiferromagnet YMn{sub 1?x}Fe{sub x}O{sub 3} (x ? 0.5) has been investigated. The neutron diffraction analysis shows that the structure of these polycrystalline samples changes from hexagonal phase (space group P6{sub 3}cm) to orthorhombic phase (space group Pnma) for x?>?0.2. The frustration parameter decreases with Fe substitution. All the compounds are antiferromagnetic, and the magnetic structure is described as a mixture of ?3 and ?4 irreducible representation (IR) in the hexagonal phase, and the ratio of these two IRs is found to vary with Fe doping (x???0.2). A continuous spin reorientation as a function of temperature is observed in these samples. The magnetic ground state in the orthorhombic phase of the higher doped samples (x???0.3) is explained by taking ?1 (G{sub x}C{sub y}A{sub z}) representation of Pnma setting. In YMnO{sub 3} suppression of dielectric constant ?? is observed below T{sub N} indicative of magnetoelectric coupling. This anomalous behavior reduces in Fe doped samples. The dielectric constant is found to be correlated with the magnetic moment (M) obtained from neutron diffraction experiments and follows a M{sup 2} behavior close to T{sub N} in agreement with Landau theory.

  20. Spin 1 particle in the magnetic monopole potential, nonrelativistic approximation. Minkowski and Lobachevski spaces

    E-Print Network [OSTI]

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

    2015-01-17

    The spin 1 particle is treated in the presence of the Dirac magnetic monopole in the Minkowski and Lobachevsky spaces. Separating the variables in the frame of the matrix 10-component Duffin-Kemer-Petiau approach (wave equation) and making a nonrelativistic approximation in the corresponding radial equations, a system of three coupled second order linear differential equations is derived for each type of geometry. For the Minkowski space, the nonrelativistic equations are disconnected using a linear transformation, which makes the mixing matrix diagonal. The resultant three unconnected equations involve three routs of a cubic algebraic equation as parameters. The approach allows extension to the case of additional external spherically symmetric fields. The Coulomb and oscillator potentials are considered and for each of these cases three series of energy spectra are derived. A special attention is given to the states with minimum value of the total angular momentum. In the case of the curved background of the Lobachevsky geometry, the mentioned linear transformation does not disconnect the nonrelativistic equations in the presence of the monopole. Nevertheless, we derive the solution of the problem in the case of minimum total angular momentum. In this case, we additionally involve a Coulomb or oscillator field. Finally, considering the case without the monopole field, we show that for both Coulomb and oscillator potentials the problem is reduced to a system of three differential equations involving a hypergeometric and two general Heun equations. Imposing on the parameters of the latter equations a specific requirement, reasonable from the physical standpoint, we derive the corresponding energy spectra.

  1. Modeling of the magnetic behavior of -Fe2O3 nanoparticles mineralized in ferritin

    E-Print Network [OSTI]

    Idzerda, Yves

    Modeling of the magnetic behavior of -Fe2O3 nanoparticles mineralized in ferritin Damon Resnick maghemite mineralized inside ferritin protein cages has been investigated with a vibrating sample be emptied of its con- tents and mineralized with a multitude of different materials, forming highly uniform

  2. Magnetic and structural behavior of FeCo/Cu multilayers submitted to Kr irradiation

    E-Print Network [OSTI]

    Penkov, Julian Geshev

    Magnetic and structural behavior of FeCo/Cu multilayers submitted to Kr irradiation I.L. Graff Cedex, France Available online 19 January 2007 Abstract We have studied the effects of ion irradiation a phase transformation of FeCo alloy from bcc for the as-deposited sample to fcc after irradiation

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

    SciTech Connect (OSTI)

    Vaknin, D.; Garlea, Vasile O; Demmel, F.; Mamontov, Eugene; Nojiri, H; Martin, Catalin; Chiorescu, Irinel; Qiu, Y.; Luban, M.; Kogerler, P.; Fielden, J.; Engelhardt, L; Rainey, C

    2010-01-01

    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.

  4. 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)

    2014-04-07

    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.

  5. Magnetic behavior of 360° domain walls in patterned magnetic thin films

    E-Print Network [OSTI]

    Mascaro, Mark Daniel

    2012-01-01

    360° transverse domain walls (360DWs), which form readily from transverse 180° domain walls (180DWs) of opposite sense, demonstrate qualitatively distinct behaviors from their constituent 180DWs and are therefore of interest ...

  6. 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

    2003-05-31

    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?

  7. 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)

    2014-03-07

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

  8. Magnetic moment, vorticity-spin coupling and parity-odd conductivity of chiral fermions in 4-dimensional Wigner functions

    E-Print Network [OSTI]

    Jian-hua Gao; Qun Wang

    2015-04-28

    We demonstrate the emergence of the magnetic moment and spin-vorticity coupling of chiral fermions in 4-dimensional Wigner functions. In linear response theory with space-time varying electromagnetic fields, the parity-odd part of the electric conductivity can also be derived which reproduces results of the one-loop and the hard-thermal or hard-dense loop. All these properties show that the 4-dimensional Wigner functions capture comprehensive aspects of physics for chiral fermions in electromagnetic fields.

  9. Magnetic moment, vorticity-spin coupling and parity-odd conductivity of chiral fermions in 4-dimensional Wigner functions

    E-Print Network [OSTI]

    Jian-hua Gao; Qun Wang

    2015-08-26

    We demonstrate the emergence of the magnetic moment and spin-vorticity coupling of chiral fermions in 4-dimensional Wigner functions. In linear response theory with space-time varying electromagnetic fields, the parity-odd part of the electric conductivity can also be derived which reproduces results of the one-loop and the hard-thermal or hard-dense loop. All these properties show that the 4-dimensional Wigner functions capture comprehensive aspects of physics for chiral fermions in electromagnetic fields.

  10. Spin-glass behavior of A Fe sub 4 Al sub 8 ( A =Th,U,Np) intermetallics

    SciTech Connect (OSTI)

    Gal, J. Nuclear Research Center, 84190 Beer-Sheva Physik Department E15, Technische Universitaet Muenchen, D-8046 Garchingbei Muenchen ); Yaar, I.; Regev, D.; Fredo, S.; Shani, G.; Arbaboff, E. Nuclear Research Center, 84190 Beer-Sheva ); Potzel, W.; Aggarwal, K.; Pereda, J.A.; Kalvius, G.M. ); Litterst, F.J. Physik Department E15, Technische Universitaet Muenchen, D-8046 Garching bei Muenchen ); Schaefer, W.; Will, G. Kernforschonganlage, D-5170 Juelich )

    1990-11-01

    Combined ac- and dc-susceptibility, neutron-diffraction, and Moessbauer studies of UFe{sub 4}Al{sub 8}, NpFe{sub 4}Al{sub 8}, and ThFe{sub 4}Al{sub 8} argue for the establishment of a spin-glass (SG) state below {ital T}{sub SG}({ital B}{r arrow}0){approx}130, 120, and 110 K, respectively. The SG temperature {ital T}{sub SG}({ital B}) decreases with application of external magnetic field {ital B}. The ac susceptibility ({chi}{sub ac}) shows a sharp cusp at {ital T}{sub SG}({ital B}{approx}0). The isothermal and thermoremanent magnetization differ markedly and show temperature-dependent irreversibilities below {ital T}{sub SG}({ital B}). The Moessbauer spectra reveal onset of hyperfine splitting, indicating frozen spins below {ital T}{sub SG}(0). The neutron-diffraction studies of UFe{sub 4}Al{sub 8} and NpFe{sub 4}Al{sub 8} show that after switching off the external magnetic field greater than 3 T the U and Np momenta (2{ital a} site) are frozen parallel to the direction of the external field. We label the freezing temperature under high external fields {ital T}{sub OG}, and show that it serves as the upper limit of {ital T}{sub SG}({ital B}) with {ital T}{sub SG}({ital B}{r arrow}0){r arrow}{ital T}{sub OG}. For concentrated SG systems, {ital T}{sub SG}(0) is a reproducible value, independent of the observation time window, which indicates a true thermodynamic phase transition; the cusp in {chi}{sub ac}, however, is not necessarily a confirmation for the establishment of a SG state.

  11. Synthesis, structure, and magnetic properties of spin-1/2 kagomé antiferromagnets

    E-Print Network [OSTI]

    Nytko, Emily A

    2008-01-01

    Stoichiometrically pure S = 1/2 Cu2+ kagomé materials have been synthesized. Such materials provide an ideal venue for exploration of quantum states on a kagomé because they exhibit strong geometric spin frustration and ...

  12. Optically induced spin wave dynamics in [Co/Pd]{sub 8} antidot lattices with perpendicular magnetic anisotropy

    SciTech Connect (OSTI)

    Pal, S.; Das, K.; Barman, A., E-mail: abarman@ybose.res.in [Thematic Unit of Excellence on Nanodevice Technology and Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Klos, J. W.; Gruszecki, P.; Krawczyk, M., E-mail: krawczyk@amu.edu.pl [Faculty of Physics, A. Mickiewicz University in Poznan, Umultowska 85, 61-614 Pozna? (Poland); Hellwig, O. [San Jose Research Center, HGST, a Western Digital Company, 3403 Yerba Buena Rd., San Jose, California 95135 (United States)

    2014-10-20

    We present an all-optical time-resolved measurement of spin wave (SW) dynamics in a series of antidot lattices based on [Co(0.75?nm)/Pd(0.9?nm)]{sub 8} multilayer (ML) systems with perpendicular magnetic anisotropy. The spectra depend significantly on the areal density of the antidots. The observed SW modes are qualitatively reproduced by the plane wave method. The interesting results found in our measurements and calculations at small lattice constants can be attributed to the increase of areal density of the shells with modified magnetic properties probably due to distortion of the regular ML structure by the Ga ion bombardment and to increased coupling between localized modes. We propose and discuss the possible mechanisms for this coupling including exchange interaction, tunnelling, and dipolar interactions.

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

    E-Print Network [OSTI]

    Garmestani, Hamid

    for 30 s at a heating rate1 Crystallization Behavior, Nanostructure and Magnetic Properties of Melt-spun (Nd,Pr,Dy)2(Fe,Co,Mo)14B/-Fe Nanocomposite Magnets B. Z. Cui 1, 2 *, K. Han 1 , Y. Zhang 3 , J. P. Liu 2 , H. Garmestani 1

  14. Electric field induced spin and valley polarization within a magnetically confined silicene channel

    SciTech Connect (OSTI)

    Liu, Yiman; Zhou, Xiaoying; Zhou, Ma; Zhou, Guanghui; Long, Meng-Qiu

    2014-12-28

    We study the electronic structure and transport properties of Dirac electrons along a channel created by an exchange field through the proximity of ferromagnets on a silicene sheet. The multiple total internal reflection induces localized states in the channel, which behaves like an electron waveguide. An effect of spin- and valley-filtering originating from the coupling between valley and spin degrees is predicted for such a structure. Interestingly, this feature can be tuned significantly by locally applying electric and exchange fields simultaneously. The parameter condition for observing fully spin- and valley-polarized current is obtained. These findings may be observable in todays' experimental technique and useful for spintronic and valleytronic applications based on silicene.

  15. Interacting spins and holes in zigzag edge nanographene

    SciTech Connect (OSTI)

    Dutta, Sudipta; Wakabayashi, Katsunori

    2013-12-04

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

  16. Determination of the Fe magnetic anisotropies and the CoO frozen spins in epitaxial CoO/Fe/Ag(001)

    SciTech Connect (OSTI)

    Meng, J. Li, Y.; Park, J. S.; Jenkins, C. A.; Arenholz, E.; Scholl, A.; Tan, A.; Son, H.; Zhao, H. W.; Hwang, Chanyong; Qiu, Z. Q.

    2011-04-28

    CoO/Fe/Ag(001) films were grown epitaxially and studied by X-ray Magnetic Circular Dichroism (XMCD) and X-ray Magnetic Linear Dichroism (XMLD). After field cooling along the Fe[100] axis to 80 K, exchange bias, uniaxial anisotropy, and 4-fold anisotropy of the films were determined by hysteresis loop and XMCD measurements by rotating the Fe magnetization within the film plane. The CoO frozen spins were determined by XMLD measurement as a function of CoO thickness.We find that among the exchange bias, uniaxial anisotropy, and 4-fold anisotropy, only the uniaxial magnetic anisotropy follows thickness dependence of the CoO frozen spins.

  17. 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

    2014-04-08

    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.

  18. Spin waves in circular soft magnetic dots at the crossover between vortex and single domain state

    E-Print Network [OSTI]

    Metlushko, Vitali

    Facility, Cornell University, Ithaca, New York, 14853 USA 6Departamento de Fisica de Materiales We report on linear spin dynamics in the vortex state of Permalloy cylindrical dots subjected In many physical systems such as liquids, plasma, super- conductors, ferromagnets, etc., the topological

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

    SciTech Connect (OSTI)

    Punnoose, A. Dodge, Kelsey; Reddy, K. M.; Franco, Nevil; Chess, Jordan; Eixenberger, Josh; Beltrán, J. J.; Barrero, C. A.

    2014-05-07

    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.

  20. 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

    2004-09-12

    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.

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

    E-Print Network [OSTI]

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

    2010-09-27

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

  2. 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

  3. Electronic structure and magnetic behavior of UMn/sub 2/ and UFe/sub 2/

    SciTech Connect (OSTI)

    Boring, A.M.; Albers, R.C.; Schadler, G.H.; Lawson, A.C.; Weinberger, P.; Christensen, N.E.

    1987-10-01

    The electronic structure of UMn/sub 2/ and UFe/sub 2/ has been determined using the first-principles self-consistent spin-polarized scalar-relativistic linear muffin-tin-orbital method. The calculations were performed at several lattice spacings for these materials in the C15 (cubic Laves phase) crystal structure. In agreement with experimental data it is found that UMn/sub 2/ is almost nonmagnetic (small moments on the sites) whereas in UFe/sub 2/ both U and Fe sites have appreciable moments. Furthermore, the magnetism in these systems is determined by exchange splitting and not by charge-transfer effects. The calculated moments in UFe/sub 2/ are larger at the U sites than those seen experimentally. The total moment in UFe/sub 2/ is somewhat insensitive to changes in lattice spacing (over the limited range determined) while the moments on individual sites are very sensitive to this variation.

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

    SciTech Connect (OSTI)

    Ross, N. Kostylev, M.; Stamps, R. L.

    2014-09-21

    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.

  5. Magnetoelastics of a spin liquid : x-ray diffraction studies of Tb{sub 2}Ti{sub 2}O{sub 7} in pulsed magnetic fields.

    SciTech Connect (OSTI)

    Ruff, J. P. C.; Islam, Z.; Clancy, J. P.; Ross, K. A.; Nojiri, H.; Matsuda, Y. H.; Dabkowska, H. A.; Dabkowski, A. D.; Gaulin, B. D.; X-Ray Science Division; McMaster Univ.; Tohoku Univ.; Univ. of Tokyo; Canadian Inst. for Advanced Research; Brockhouse Inst. for Materials Research

    2010-08-13

    We report high resolution single crystal x-ray diffraction measurements of the frustrated pyrochlore magnet Tb{sub 2}Ti{sub 2}O{sub 7}, collected using a novel low temperature pulsed magnet system. This instrument allows characterization of structural degrees of freedom to temperatures as low as 4.4 K, and in applied magnetic fields as large as 30 T. We show that Tb{sub 2}Ti{sub 2}O{sub 7} manifests intriguing structural effects under the application of magnetic fields, including strongly anisotropic giant magnetostriction, a restoration of perfect pyrochlore symmetry in low magnetic fields, and ultimately a structural phase transition in high magnetic fields. It is suggested that the magnetoelastic coupling thus revealed plays a significant role in the spin liquid physics of Tb{sub 2}Ti{sub 2}O{sub 7} at low temperatures.

  6. Kinetic effects on double hysteresis in spin crossover molecular magnets analyzed with first order reversal curve diagram technique

    SciTech Connect (OSTI)

    Stan, Raluca-Maria; Gaina, Roxana; Enachescu, Cristian E-mail: radu.tanasa@uaic.ro; Stancu, Alexandru; Tanasa, Radu E-mail: radu.tanasa@uaic.ro; Bronisz, Robert

    2015-05-07

    In this paper, we analyze two types of hysteresis in spin crossover molecular magnets compounds in the framework of the First Order Reversal Curve (FORC) method. The switching between the two stable states in these compounds is accompanied by hysteresis phenomena if the intermolecular interactions are higher than a threshold. We have measured the static thermal hysteresis (TH) and the kinetic light induced thermal hysteresis (LITH) major loops and FORCs for the polycrystalline Fe(II) spin crossover compound [Fe{sub 1?x}Zn{sub x}(bbtr){sub 3}](ClO{sub 4}){sub 2} (bbtr?=?1,4-di(1,2,3-triazol-1-yl)butane), either in a pure state (x?=?0) or doped with Zn ions (x?=?0.33) considering different sweeping rates. Here, we use this method not only to infer the domains distribution but also to disentangle between kinetic and static components of the LITH and to estimate the changes in the intermolecular interactions introduced by dopants. We also determined the qualitative relationship between FORC distributions measured for TH and LITH.

  7. 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: drGraf@t-online.de; Clasen, Stephan

    2014-06-15

    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.

  8. Current-induced spin-orbit torque switching of perpendicularly magnetized Hf|CoFeB|MgO and Hf|CoFeB|TaO{sub x} structures

    SciTech Connect (OSTI)

    Akyol, Mustafa; Yu, Guoqiang; Alzate, Juan G.; Upadhyaya, Pramey; Li, Xiang; Wong, Kin L.; Khalili Amiri, Pedram; Wang, Kang L.; Ekicibil, Ahmet

    2015-04-20

    We study the effect of the oxide layer on current-induced perpendicular magnetization switching properties in Hf|CoFeB|MgO and Hf|CoFeB|TaO{sub x} tri-layers. The studied structures exhibit broken in-plane inversion symmetry due to a wedged CoFeB layer, resulting in a field-like spin-orbit torque (SOT), which can be quantified by a perpendicular (out-of-plane) effective magnetic field. A clear difference in the magnitude of this effective magnetic field (H{sub z}{sup FL}) was observed between these two structures. In particular, while the current-driven deterministic perpendicular magnetic switching was observed at zero magnetic bias field in Hf|CoFeB|MgO, an external magnetic field is necessary to switch the CoFeB layer deterministically in Hf|CoFeB|TaO{sub x}. Based on the experimental results, the SOT magnitude (H{sub z}{sup FL} per current density) in Hf|CoFeB|MgO (?14.12?Oe/10{sup 7} A cm{sup ?2}) was found to be almost 13× larger than that in Hf|CoFeB|TaO{sub x} (?1.05?Oe/10{sup 7} A cm{sup ?2}). The CoFeB thickness dependence of the magnetic switching behavior, and the resulting ?H{sub z}{sup FL} generated by in-plane currents are also investigated in this work.

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

    SciTech Connect (OSTI)

    Chen, C.-C.

    2010-04-29

    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.

  10. 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)

    2005-12-01

    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.

  11. Probing nanoscale behavior of magnetic materials with soft x-ray spectromicroscopy

    E-Print Network [OSTI]

    Fischer, Peter

    2014-01-01

    spin electronics or spintronics [3], where in addition tomagnetic materials for spintronics ap- plications, where the

  12. 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.

    2014-06-21

    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.

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

    SciTech Connect (OSTI)

    Afshar, Mahdi; Sargolzaei, Mohsen

    2013-11-15

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

  14. Measuring nonequilibrium retarded spin-spin Green's functions in an ion-trap based quantum simulator

    E-Print Network [OSTI]

    Bryce T. Yoshimura; J. K. Freericks

    2015-12-16

    Recent work proposed a variant on Ramsey interferometry for coupled spin-$1/2$ systems that directly measures the retarded spin-spin Green's function. We expand on that work by investigating nonequilibrium retarded spin-spin Green's functions within the transverse-field Ising model. We derive the lowest four spectral moments to understand the short-time behavior and we employ a Lehmann-like representation to determine the spectral behavior. We simulate a Ramsey protocol for a nonequilibrium quantum spin system that consists of a coherent superposition of the ground state and diabatically excited higher-energy states via a temporally ramped transverse magnetic field. We then apply the Ramsey spectroscopy protocol to the final Hamiltonian, which has a constant transverse field. The short-time behavior directly relates to Lieb-Robinson bounds for the transport of many-body correlations, while the long-time behavior relates to the excitation spectra of the Hamiltonian. Compressive sensing is employed in the data analysis to efficiently extract that spectra.

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

    SciTech Connect (OSTI)

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

    2014-06-10

    Intermittent pulsars are part-time radio pulsars. They have higher slow down rates in the on state (radio-loud) than in the off state (radio-quiet). This gives evidence that particle wind may play an important role in pulsar spindown. The effect of particle acceleration is included in modeling the rotational energy loss rate of the neutron star. Applying the pulsar wind model to the three intermittent pulsars (PSR B1931+24, PSR J1841–0500, and PSR J1832+0029) allows their magnetic fields and inclination angles to be calculated simultaneously. The theoretical braking indices of intermittent pulsars are also given. In the pulsar wind model, the density of the particle wind can always be the Goldreich-Julian density. This may ensure that different on states of intermittent pulsars are stable. The duty cycle of particle wind can be determined from timing observations. It is consistent with the duty cycle of the on state. Inclination angle and braking index observations of intermittent pulsars may help to test different models of particle acceleration. At present, the inverse Compton scattering induced space charge limited flow with field saturation model can be ruled out.

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

    SciTech Connect (OSTI)

    Cuello, N.; Elías, V.; Crivello, M.; Oliva, M.; Eimer, G.

    2013-09-15

    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.

  17. Effects of strain and quantum confinement in optically pumped nuclear magnetic resonance in GaAs: Interpretation guided by spin-dependent band structure calculations

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

    Wood, R. M.; Saha, D.; McCarthy, L. A.; Tokarski, III, J. T.; Sanders, G. D.; Kuhns, P. L.; McGill, S. A.; Reyes, A. P.; Reno, J. L.; Stanton, C. J.; et al

    2014-10-29

    A combined experimental-theoretical study of optically pumped NMR (OPNMR) has been performed in a GaAs/Al0.1Ga0.9As quantum well film with thermally induced biaxial strain. The photon energy dependence of the Ga-71 OPNMR signal was recorded at magnetic fields of 4.9 and 9.4 T at a temperature of 4.8-5.4 K. The data were compared to the nuclear spin polarization calculated from differential absorption to spin-up and spin-down states of the conduction band using a modified Pidgeon Brown model. Reasonable agreement between theory and experiment is obtained, facilitating assignment of features in the OPNMR energy dependence to specific interband transitions. Despite the approximationsmore »made in the quantum-mechanical model and the inexact correspondence between the experimental and calculated observables, the results provide insight into how effects of strain and quantum confinement are manifested in OPNMR signals« less

  18. Insulating state to quantum Hall-like state transition in a spin-orbit-coupled two-dimensional electron system

    SciTech Connect (OSTI)

    Lo, Shun-Tsung; Hsu, Chang-Shun [Graduate Institute of Applied Physics, National Taiwan University, Taipei 10617, Taiwan (China); Lin, Y. M.; Lin, S.-D.; Lee, C. P. [Department of Electronics Engineering and Institute of Electronics, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Ho, Sheng-Han; Chuang, Chiashain; Wang, Yi-Ting [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Liang, C.-T. [Graduate Institute of Applied Physics, National Taiwan University, Taipei 10617, Taiwan (China); Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China)

    2014-07-07

    We study interference and interactions in an InAs/InAsSb two-dimensional electron system. In such a system, spin-orbit interactions are shown to be strong, which result in weak antilocalization (WAL) and thereby positive magnetoresistance around zero magnetic field. After suppressing WAL by the magnetic field, we demonstrate that classical positive magnetoresistance due to spin-orbit coupling plays a role. With further increasing the magnetic field, the system undergoes a direct insulator-quantum Hall transition. By analyzing the magnetotransport behavior in different field regions, we show that both electron-electron interactions and spin-related effects are essential in understanding the observed direct transition.

  19. Dependence of the colored frequency noise in spin torque oscillators on current and magnetic field

    SciTech Connect (OSTI)

    Eklund, Anders Sani, Sohrab R.; Chung, Sunjae; Amir Hossein Banuazizi, S.; Östling, Mikael; Gunnar Malm, B.; Bonetti, Stefano; Majid Mohseni, S.; Persson, Johan; Iacocca, Ezio; Åkerman, Johan

    2014-03-03

    The nano-scale spin torque oscillator (STO) is a compelling device for on-chip, highly tunable microwave frequency signal generation. Currently, one of the most important challenges for the STO is to increase its longer-time frequency stability by decreasing the 1/f frequency noise, but its high level makes even its measurement impossible using the phase noise mode of spectrum analyzers. Here, we present a custom made time-domain measurement system with 150?MHz measurement bandwidth making possible the investigation of the variation of the 1/f as well as the white frequency noise in a STO over a large set of operating points covering 18–25?GHz. The 1/f level is found to be highly dependent on the oscillation amplitude-frequency non-linearity and the vicinity of unexcited oscillation modes. These findings elucidate the need for a quantitative theoretical treatment of the low-frequency, colored frequency noise in STOs. Based on the results, we suggest that the 1/f frequency noise possibly can be decreased by improving the microstructural quality of the metallic thin films.

  20. A New Spin on Photoemission Spectroscopy

    SciTech Connect (OSTI)

    Advanced Light Source; Jozwiak, Chris

    2008-12-18

    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.

  1. Deconvolution of mixed magnetism in multilayer graphene

    SciTech Connect (OSTI)

    Swain, Akshaya Kumar; Bahadur, Dhirendra

    2014-06-16

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

  2. 1784 IEEE TRANSACTIONS ON MAGNETICS, VOL. 40, NO. 4, JULY 2004 A Behavioral Model for Frequency-Dependent

    E-Print Network [OSTI]

    Vu-Quoc, Loc

    ferrites. I. INTRODUCTION COMPUTER-AIDED design of power-electronic systems often involves the simulation behavior to each elementary loop to synthesize the finite switching rate between magnetization polarities applied to computer-aided design in [3]. At the macroscopic level, rate-dependent hysteresis is taken

  3. Dy-V magnetic interaction and local structure bias on the complex spin and orbital ordering in Dy??xTbxVO? (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.

    2013-06-01

    The spin and orbital ordering in Dy??xTbxVO? (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 fieldsmore »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 Dy??xTbxVO?.« less

  4. 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)

    2013-08-15

    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}.

  5. 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.; Ralph, D. C.

    2014-09-08

    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).

  6. Generation of Dark and Bright Spin Wave Envelope Soliton Trains through Self-Modulational Instability in Magnetic Films

    E-Print Network [OSTI]

    Patton, Carl

    Generation of Dark and Bright Spin Wave Envelope Soliton Trains through Self-Modulational spin wave envelope soliton trains from a continuous wave input signal due to spontaneous modulational instability has been observed for the first time. The dark soliton trains were formed from high dispersion

  7. Spin-orbit Coupling Induced Magnetism in the d-density Wave Phase of La2-xBaxCuO4 Superconductors

    SciTech Connect (OSTI)

    Wu, Congjun; /Stanford U., Phys. Dept. /Santa Barbara, KITP; Zaanen, Jan; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-01-15

    We study the effects of spin-orbit coupling in the d-density wave (DDW) phase. In the low-temperature orthorhombic phase of La{sub 2-x}Ba{sub x}CuO{sub 4}, we find that spin-orbit coupling induces ferromagnetic moments in the DDW phase, which are polarized along the [110] direction with a considerable magnitude. This effect does not exist in the superconducting phase. On the other hand, if the d-density wave order does not exist at zero field, a magnetic field along the [110] direction always induces such a staggered orbital current. We discuss experimental constraints on the DDW states in light of our theoretical predictions.

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

    E-Print Network [OSTI]

    Juerg Froehlich

    2008-02-29

    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.

  9. Spin-noise correlations and spin-noise exchange driven by low-field spin-exchange collisions

    E-Print Network [OSTI]

    A. T. Dellis; M. Loulakis; I. K. Kominis

    2014-09-28

    The physics of spin exchange collisions have fueled several discoveries in fundamental physics and numerous applications in medical imaging and nuclear magnetic resonance. We here report on the experimental observation and theoretical justification of spin-noise exchange, the transfer of spin-noise from one atomic species to another. The signature of spin-noise exchange is an increase of the total spin-noise power at low magnetic fields, on the order of 1 mG, where the two-species spin-noise resonances overlap. The underlying physical mechanism is the two-species spin-noise correlation induced by spin-exchange collisions.

  10. Effects of antiferro-ferromagnetic phase coexistence and spin fluctuations on the magnetic and related properties of NdCuSi

    SciTech Connect (OSTI)

    Gupta, Sachin E-mail: suresh@phy.iitb.ac.in; Suresh, K. G. E-mail: suresh@phy.iitb.ac.in; Das, A.; Nigam, A. K.; Hoser, A.

    2015-06-01

    Polycrystalline NdCuSi is found to show co-existence of antiferromagnetic (AFM) and ferromagnetic (FM) phases at low temperatures, as revealed by neutron diffraction data. The coexistence is attributed to the competing exchange interactions and crystal field effect. The compound shows a large, low-field magnetoresistance (MR) of ? ? 32% at 20 kOe below T{sub N} (3.1 K), which becomes ? ? 36% at 50 kOe. The MR value at 50 kOe is found to be the highest among the RTX compounds. Magnetocaloric effect (MCE) is also found to show a large value of ?11 J/kg K close to T{sub N}. Resistivity data show the presence of spin fluctuations, which get suppressed by the applied field. Large MR and MCE in this compound arise due to the coexistence of the two phases. The field dependencies of MR and MCE show quadratic behavior, confirming the presence of spin fluctuations.

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

    SciTech Connect (OSTI)

    Farghadan, R.; Saffarzadeh, A.

    2014-05-07

    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.

  12. 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)

    2008-12-31

    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.

  13. Probing nanoscale behavior of magnetic materials with soft x-ray spectromicroscopy

    E-Print Network [OSTI]

    Fischer, Peter

    2014-01-01

    seen as one of the ?rst spintronic effects. Very soon afterstructure and magnetism in spintronic-, complex oxide- and

  14. 3494 IEEETRANSACTIONS ON MAGNETICS, VOL. MAG-23, NO. 5 , SEPTEMBER 1987 BRILLOUIN LIGHT SCATTERING STUDYOr' THE SPIN WAVE STIFFNESS PARAMETERIN

    E-Print Network [OSTI]

    Patton, Carl

    STUDYOr' THE SPIN WAVE STIFFNESS PARAMETERIN SC-SUBSTITUTED LUTETIUM-YTTRIUM IRON GARNET J . G . Booth, G measured for a seriesof Sc substituted lutetium-yttrium iron garnet(YIG) liquid phase epitaxy thin films

  15. Effects of strain and quantum confinement in optically pumped nuclear magnetic resonance in GaAs: Interpretation guided by spin-dependent band structure calculations

    SciTech Connect (OSTI)

    Wood, R. M.; Saha, D.; McCarthy, L. A.; Tokarski, III, J. T.; Sanders, G. D.; Kuhns, P. L.; McGill, S. A.; Reyes, A. P.; Reno, J. L.; Stanton, C. J.; Bowers, C. R.

    2014-10-29

    A combined experimental-theoretical study of optically pumped NMR (OPNMR) has been performed in a GaAs/Al0.1Ga0.9As quantum well film with thermally induced biaxial strain. The photon energy dependence of the Ga-71 OPNMR signal was recorded at magnetic fields of 4.9 and 9.4 T at a temperature of 4.8-5.4 K. The data were compared to the nuclear spin polarization calculated from differential absorption to spin-up and spin-down states of the conduction band using a modified Pidgeon Brown model. Reasonable agreement between theory and experiment is obtained, facilitating assignment of features in the OPNMR energy dependence to specific interband transitions. Despite the approximations made in the quantum-mechanical model and the inexact correspondence between the experimental and calculated observables, the results provide insight into how effects of strain and quantum confinement are manifested in OPNMR signals

  16. 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

  17. 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)

    2012-03-19

    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.

  18. 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

    2005-06-14

    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.

  19. Probing nanoscale behavior of magnetic materials with soft x-ray spectromicroscopy

    E-Print Network [OSTI]

    Fischer, Peter

    2014-01-01

    seen as one of the ?rst spintronic effects. Very soon afterstructure and magnetism in spintronic-, complex oxide- andspin electronics or spintronics [3], where in addition to

  20. Pauli equation for a charged spin particle on a curved surface in an electric and magnetic field

    E-Print Network [OSTI]

    Yong-Long Wang; Long Du; Chang-Tan Xu; Xiao-Jun Liu; Hong-Shi Zong

    2014-11-05

    We derive the Pauli equation for a charged spin particle confined to move on a spatially curved surface $\\mathcal{S}$ in an electromagnetic field. Using the thin-layer quantization scheme to constrain the particle on $\\mathcal{S}$, and in the transformed spinor representations, we obtain the well-known geometric potential $V_g$ and the presence of $e^{-i\\varphi}$, which can generate additive spin connection geometric potentials by the curvilinear coordinate derivatives, and we find that the two fundamental evidences in the literature [Giulio Ferrari and Giampaolo Cuoghi, Phys. Rev. Lett. 100, 230403 (2008).] are still valid in the present system without source current perpendicular to $\\mathcal{S}$. Finally, we apply the surface Pauli equation to spherical, cylindrical, and toroidal surfaces, in which we obtain expectantly the geometric potentials and new spin connection geometric potentials, and find that only the normal Pauli matrix appears in these equations.

  1. 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

  2. Controllable fully spin-polarized transport in a ferromagnetically doped topological insulator junction

    SciTech Connect (OSTI)

    Zhou, Benliang; Tang, Dongsheng; Zhou, Guanghui, E-mail: ghzhou@hunnu.edu.cn [Department of Physics and Key Laboratory for Low-Dimensional Quantum Structures and Manipulation (Ministry of Education), Hunan Normal University, Changsha 410081 (China); Zhou, Benhu [Department of Physics, Shaoyang University, Shaoyang 422001 (China)

    2014-04-21

    We investigate the energy band structure and the spin-dependent transport for a normal/ferromagnetic/normal two-dimension topological insulator (TI) junction. By diagonalizing Hamiltonian for the system, the band structure shows that the edge states on two sides are coupled resulting in a gap opening due to the transverse spatial confinement. Further, the exchange field induced by magnetic impurities can also modulate the band structure with two spin degenerate bands splitting. By using the nonequilibrium Green's function method, the dependence of spin-dependent conductance and spin-polarization on the Fermi energy, the exchange field strength and the ferromagnetic TI (FTI) length are also analyzed, respectively. Interestingly, the degenerate conductance plateaus for spin-up and -down channels are broken, and both the conductances are suppressed by magnetic impurities due to the time-reversal symmetry broken and inelastic scattering. The spin-dependent conductance shows different behaviors when the Fermi energy is tuned into different ranges. Moreover, the conductance can be fully spin polarized by tuning the Fermi energy and the exchange field strength, or by tuning the Fermi energy and the FTI length. Consequently, the junction can transform from a quantum spin Hall state to a quantum anomalous Hall state, which is very important to enable dissipationless charge current for designing perfect spin filter.

  3. Sensing remote nuclear spins

    E-Print Network [OSTI]

    Nan Zhao; Jan Honert; Berhard Schmid; Junichi Isoya; Mathew Markham; Daniel Twitchen; Fedor Jelezko; Ren-Bao Liu; Helmut Fedder; Jörg Wrachtrup

    2012-04-29

    Sensing single nuclear spins is a central challenge in magnetic resonance based imaging techniques. Although different methods and especially diamond defect based sensing and imaging techniques in principle have shown sufficient sensitivity, signals from single nuclear spins are usually too weak to be distinguished from background noise. Here, we present the detection and identification of remote single C-13 nuclear spins embedded in nuclear spin baths surrounding a single electron spins of a nitrogen-vacancy centre in diamond. With dynamical decoupling control of the centre electron spin, the weak magnetic field ~10 nT from a single nuclear spin located ~3 nm from the centre with hyperfine coupling as weak as ~500 Hz is amplified and detected. The quantum nature of the coupling is confirmed and precise position and the vector components of the nuclear field are determined. Given the distance over which nuclear magnetic fields can be detected the technique marks a firm step towards imaging, detecting and controlling nuclear spin species external to the diamond sensor.

  4. 2600 IEEE TRANSACTIONS ON MAGNETICS, VOL. 41, NO. 10, OCTOBER 2005 Influence of Au Capping Layer on Spin Accumulation

    E-Print Network [OSTI]

    Otani, Yoshichika

    -torque transistor [2] have been recently proposed. Such spintronic devices have great advantage of an additional- diffusion process is thus essential to realize such spintronic de- vices. Laterally structured ferromagnetic as for the development of the above spintronic devices. Johnson and Silsbee demonstrated the electrical spin injection

  5. Fourier Magnetic Imaging with Nanoscale Resolution and Compressed Sensing Speed-up using Electronic Spins in Diamond

    E-Print Network [OSTI]

    Walsworth, Ronald L.

    1 Fourier Magnetic Imaging with Nanoscale Resolution and Compressed Sensing Speed-up using imaging.12 Here we introduce an alternative technique of Fourier magnetic imaging using NV Fourier transform to yield real-space images with nanoscale resolution, wide field-of-view (FOV

  6. Cosmic magnetism

    SciTech Connect (OSTI)

    Seymour, P.

    1986-01-01

    This book deals with the cosmic magnetism in a non-mathematical way. It uses Faraday's very powerful and highly pictorial concept of lines of magnetic force and their associated physical properties to explain the structure and behavior of magnetic fields in extraterrestrial objects. Contents include: forces of nature; magnetic field of earth; solar and interplanetary magnetic fields; magnetic fields in the solar system; stars and pulsars; and magnetic fields of the milky way and other galaxies.

  7. Spin caloritronics in graphene

    SciTech Connect (OSTI)

    Ghosh, Angsula; Frota, H. O.

    2015-06-14

    Spin caloritronics, the combination of spintronics with thermoelectrics, exploiting both the intrinsic spin of the electron and its associated magnetic moment in addition to its fundamental electronic charge and temperature, is an emerging technology mainly in the development of low-power-consumption technology. In this work, we study the thermoelectric properties of a Rashba dot attached to two single layer/bilayer graphene sheets as leads. The temperature difference on the two graphene leads induces a spin current, which depends on the temperature and chemical potential. We demonstrate that the Rashba dot behaves as a spin filter for selected values of the chemical potential and is able to filter electrons by their spin orientation. The spin thermopower has also been studied where the effects of the chemical potential, temperature, and also the Rashba term have been observed.

  8. Measuring the Magnetic Center Behavior of an ILC Superconducting Quadrupole Prototype

    SciTech Connect (OSTI)

    Spencer, Cherrill M.; Adolphsen, Chris; Berndt, Martin; Jensen, David R.; Rogers, Ron; Sheppard, John C.; Lorant, Steve St; Weber, Thomas B.; Weisend, John, II; /SLAC; Brueck, Heinrich; /DESY; Toral, Fernando; /Madrid, CIEMAT

    2011-02-07

    The main linacs of the proposed International Linear Collider (ILC) consist of superconducting cavities operated at 2K. The accelerating cavities are contained in a contiguous series of cryogenic modules that also house the main linac quadrupoles, thus the quadrupoles also need to be superconducting. In an early ILC design, these magnets are about 0.6 m long, have cos (2{theta}) coils, and operate at constant field gradients up to 60 T/m. In order to preserve the small beam emittances in the ILC linacs, the e+ and e- beams need to traverse the quadrupoles near their magnetic centers. A quadrupole shunting technique is used to measure the quadrupole alignment with the beams; this process requires the magnetic centers move by no more than about 5 micrometers when their strength is changed. To determine if such tight stability is achievable in a superconducting quadrupole, we at SLAC measured the magnetic center motions in a prototype ILC quadrupole built at CIEMAT in Spain. A rotating coil technique was used with a better than 0.1 micrometer precision in the relative field center position, and less than a 2 micrometer systematic error over 30 minutes. This paper describes the warm-bore cryomodule that houses the quadrupole in its Helium vessel, the magnetic center measurement system, the measured center data and strength and harmonics magnetic data.

  9. Effects of boron composition on tunneling magnetoresistance ratio and microstructure of CoFeB/MgO/CoFeB pseudo-spin-valve magnetic tunnel junctions

    SciTech Connect (OSTI)

    Kodzuka, M.; Ohkubo, T.; Hono, K.; Ikeda, S.; Ohno, H.; Gan, H. D.

    2012-02-15

    The effect of B concentration on the tunneling magnetoresistance (TMR) of (Co{sub 25}Fe{sub 75}){sub 100-x}B{sub x}/MgO/(Co{sub 25}Fe{sub 75}){sub 100-x}B{sub x} (x = 22 and 33) pseudo-spin-valve (P-SV) magnetic tunnel junctions (MTJs) was investigated. The TMR ratios for optimally annealed MTJs with x = 22 and 33 were 340% and 170%, respectively, at room temperature. High resolution transmission electron microscopy (HRTEM) observation showed a weaker (001) texture in the MgO barrier in the MTJ with x = 33. The bottom electrode was not fully crystallized even with a considerable amount of B in the (Co{sub 25}Fe{sub 75}){sub 67}B{sub 33}, while good epitaxy was observed between (001) textured MgO and (Co{sub 25}Fe{sub 75}){sub 78}B{sub 22} electrodes.

  10. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy

    SciTech Connect (OSTI)

    Lin, Wenzhi; Foley, Andrew; Alam, Khan; Wang, Kangkang; Liu, Yinghao; Chen, Tianjiao; Pak, Jeongihm; Smith, Arthur R.

    2014-04-15

    Based on the interest in, as well as exciting outlook for, nitride semiconductor based structures with regard to electronic, optoelectronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin-polarized scanning tunneling microscopy (STM), a technique capable of achieving magnetic resolution down to the atomic scale. However, the delicate surfaces of these materials are easily corrupted by in-air transfers, making it unfeasible to study them in stand-alone ultra-high vacuum STM facilities. Therefore, we have carried out the development of a hybrid system including a nitrogen plasma assisted molecular beam epitaxy/pulsed laser epitaxy facility for sample growth combined with a low-temperature, spin-polarized scanning tunneling microscope system. The custom-designed molecular beam epitaxy growth system supports up to eight sources, including up to seven effusion cells plus a radio frequency nitrogen plasma source, for epitaxially growing a variety of materials, such as nitride semiconductors, magnetic materials, and their hetero-structures, and also incorporating in situ reflection high energy electron diffraction. The growth system also enables integration of pulsed laser epitaxy. The STM unit has a modular design, consisting of an upper body and a lower body. The upper body contains the coarse approach mechanism and the scanner unit, while the lower body accepts molecular beam epitaxy grown samples using compression springs and sample skis. The design of the system employs two stages of vibration isolation as well as a layer of acoustic noise isolation in order to reduce noise during STM measurements. This isolation allows the system to effectively acquire STM data in a typical lab space, which during its construction had no special and highly costly elements included, (such as isolated slabs) which would lower the environmental noise. The design further enables tip exchange and tip coating without breaking vacuum, and convenient visual access to the sample and tip inside a superconducting magnet cryostat. A sample/tip handling system is optimized for both the molecular beam epitaxy growth system and the scanning tunneling microscope system. The sample/tip handing system enables in situ STM studies on epitaxially grown samples, and tip exchange in the superconducting magnet cryostat. The hybrid molecular beam epitaxy and low temperature scanning tunneling microscopy system is capable of growing semiconductor-based hetero-structures with controlled accuracy down to a single atomic-layer and imaging them down to atomic resolution.

  11. Domain wall displacement by remote spin-current injection

    E-Print Network [OSTI]

    Skirdkov, P. N.

    We demonstrate numerically the ability to displace a magnetic domain wall (DW) by remote spin current injection. We consider a long and narrow magnetic nanostripe with a single DW. The spin-polarized current is injected ...

  12. 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)

    2014-05-07

    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}.

  13. 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)

    2014-07-14

    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.

  14. 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

    2014-07-18

    . In order to overcome these limits, new methods must be developed to reliably transmit and store data more efficiently. The understanding and manipulation of magnetic domain walls (DWs) may play a pivotal role in the development of new non-volatile and down...

  15. Magnetic spectroscopy and microscopy of functional materials

    E-Print Network [OSTI]

    Jenkins, C.A.

    2012-01-01

    magnetic anisotropy for spintronic devices. Appl Phys Lett,the model systems of spintronic, multiferroic, and energy-spin lifetimes [35]. Spintronic devices include spin ?lters,

  16. 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.; Guo, G. Y.; Hu, J.; Wu, R. Q.

    2014-07-07

    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.

  17. Correlation between magnetic spin structure and the three-dimensional geometry in chemically synthesized nanoscale magnetite rings

    E-Print Network [OSTI]

    Dunin-Borkowski, Rafal E.

    yielding an intermediate magnetic state between the vortex state and the tube state is found closure vortex states but in rings with thickness variations, an effective stray field occurs. Using. The interaction between exchange coupled rings leads to antiparallel vortex states and extended onion states

  18. Hysteretic behavior of Fe(phen){sub 2}(NCS){sub 2} spin-transition microparticles vs. the environment: A huge reversible component resolved by first order reversal curves

    SciTech Connect (OSTI)

    Tanasa, Radu; Stancu, Alexandru; Enachescu, Cristian; Laisney, Jérôme; Boillot, Marie-Laure

    2014-01-20

    We discuss the influence of the embedding matrix on the thermal hysteretic behavior of spin transition microparticles of Fe(phen){sub 2}(NCS){sub 2} by using a series of experimental first order reversal curves (FORCs). The shape of FORCs supports the hypothesis considering additional interactions between the spin-transition microparticles and the embedding matrix, which compares to a negative pressure on the particles. A mean-field approach based on negative variable external pressures, together with a cut off/switch on of particles-matrix interactions accounts for the experimental features.

  19. Electronic spin state of iron in lower mantle perovskite

    SciTech Connect (OSTI)

    Li, J.; Struzhkin, V.; Mao, H.-k.; Shu, J.; Hemley, R.; Fei, Y.; Mysen, B.; Dera, P.; Parapenka, V.; Shen, G.

    2010-11-16

    The electronic spin state of iron in lower mantle perovskite is one of the fundamental parameters that governs the physics and chemistry of the most voluminous and massive shell in the Earth. We present experimental evidence for spin-pairing transition in aluminum-bearing silicate perovskite (Mg,Fe)(Si,Al)O{sub 3} under the lower mantle pressures. Our results demonstrate that as pressure increases, iron in perovskite transforms gradually from the initial high-spin state toward the final low-spin state. At 100 GPa, both aluminum-free and aluminum-bearing samples exhibit a mixed spin state. The residual magnetic moment in the aluminum-bearing perovskite is significantly higher than that in its aluminum-free counterpart. The observed spin evolution with pressure can be explained by the presence of multiple iron species and the occurrence of partial spin-paring transitions in the perovskite. Pressure-induced spin-pairing transitions in the perovskite would have important bearing on the magnetic, thermoelastic, and transport properties of the lower mantle, and on the distribution of iron in the Earth's interior. The lower mantle constitutes more than half of the Earth's interior by volume (1), and it is believed to consist predominantly (80-100%) of (Mg,Fe)(Si,Al)O{sub 3} perovskite (hereafter called perovskite), with up to 20% (Mg,Fe)O ferropericlase (2). The electronic spin state of iron has direct influence on the physical properties and chemical behavior of its host phase. Hence, knowledge on the spin state of iron is important for the interpretation of seismic observations, geochemical modeling, and geodynamic simulation of the Earth's deep interior (3, 4). Crystal field theory (4, 5) and band theory (6) predicted that a high-spin to low-spin transition would occur as a result of compression. To date, no experimental data exist on the spin sate of iron in Al-bearing perovskite. To detect possible spinpairing transition of iron in perovskite under the lower mantle conditions, we measured the x-ray emission spectra of an Al-bearing perovskite sample to 100 GPa. For comparison, a parallel measurement was also carried out on an Al-free perovskite sample.

  20. Detection of atomic spin labels in a lipid bilayer using a single-spin nanodiamond probe

    E-Print Network [OSTI]

    Scholten, Robert

    Detection of atomic spin labels in a lipid bilayer using a single-spin nanodiamond probe Stefan conditions using a single-spin nanodiamond sensor. Changes in the spin relaxation time of the sensor located in a nanodiamond­­which is situated in the target structure itself and acts as a nanoscopic magnetic field detector

  1. Quantum discord in spin-cluster materials

    E-Print Network [OSTI]

    M. A. Yurischev

    2011-04-07

    The total quantum correlation (discord) in Heisenberg dimers is expressed via the spin-spin correlation function, internal energy, specific heat or magnetic susceptibility. This allows one to indirectly measure the discord through neutron scattering, as well as calorimetric or magnetometric experiments. Using the available experimental data, we found the discord for a number of binuclear Heisenberg substances with both antiferro- and ferromagnetic interactions. For the dimerized antiferromagnet copper nitrate Cu(NO_3)_2*2.5H_2O, the three independent experimental methods named above lead to a discord of approximately 0.2-0.3 bit/dimer at a temperature of 4 K. We also determined the temperature behavior of discord for hydrated and anhydrous copper acetates, as well as for the ferromagnetic binuclear copper acetate complex [Cu_2L(OAc)]*6H_2O, where L is a ligand.

  2. 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

  3. Nuclear Spins in Nanostructures

    E-Print Network [OSTI]

    W. A. Coish; J. Baugh

    2009-07-22

    We review recent theoretical and experimental advances toward understanding the effects of nuclear spins in confined nanostructures. These systems, which include quantum dots, defect centers, and molecular magnets, are particularly interesting for their importance in quantum information processing devices, which aim to coherently manipulate single electron spins with high precision. On one hand, interactions between confined electron spins and a nuclear-spin environment provide a decoherence source for the electron, and on the other, a strong effective magnetic field that can be used to execute local coherent rotations. A great deal of effort has been directed toward understanding the details of the relevant decoherence processes and to find new methods to manipulate the coupled electron-nuclear system. A sequence of spectacular new results have provided understanding of spin-bath decoherence, nuclear spin diffusion, and preparation of the nuclear state through dynamic polarization and more general manipulation of the nuclear-spin density matrix through "state narrowing". These results demonstrate the richness of this physical system and promise many new mysteries for the future.

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

    SciTech Connect (OSTI)

    Christianson, Andrew D; Goremychkin, E. A.; Gardner, J. S.; Kang, H. J.; Chung, J.-H.; Manuel, P.; Thompson, J. D.; Sarrao, J. L.; Lawrence, J. M.

    2008-01-01

    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.

  5. 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

    2015-01-01

    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.

  6. 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]

    V. G. Baryshevsky

    2015-04-25

    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.

  7. Spin Transport in Semiconductor heterostructures

    SciTech Connect (OSTI)

    Domnita Catalina Marinescu

    2011-02-22

    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.

  8. High spin polarization in CoFeMnGe equiatomic quaternary Heusler alloy

    SciTech Connect (OSTI)

    Bainsla, Lakhan; Suresh, K. G.; Nigam, A. K.; Manivel Raja, M.; Varaprasad, B. S. D. Ch. S.; Takahashi, Y. K.; Hono, K.

    2014-11-28

    We report the structure, magnetic property, and spin polarization of CoFeMnGe equiatomic quaternary Heusler alloy. The alloy was found to crystallize in the cubic Heusler structure (prototype LiMgPdSn) with considerable amount of DO{sub 3} disorder. Thermal analysis result indicated the Curie temperature is about 750?K without any other phase transformation up to melting temperature. The magnetization value was close to that predicted by the Slater-Pauling curve. Current spin polarization of P?=?0.70?±?0.01 was deduced using point contact andreev reflection measurements. The temperature dependence of electrical resistivity has been fitted in the temperature range of 5–300?K in order to check for the half metallic behavior. Considering the high spin polarization and Curie temperature, this material appears to be promising for spintronic applications.

  9. Switched Control of Electron Nuclear Spin Systems

    E-Print Network [OSTI]

    Navin Khaneja

    2007-07-11

    In this article, we study control of electron-nuclear spin dynamics at magnetic field strengths where the Larmor frequency of the nucleus is comparable to the hyperfine coupling strength. The quantization axis for the nuclear spin differs from the static B_0 field direction and depends on the state of the electron spin. The quantization axis can be switched by flipping the state of electron spin, allowing for universal control on nuclear spin states. We show that by performing a sequence of flips (each followed by a suitable delay), we can perform any desired rotation on the nuclear spins, which can also be conditioned on the state of the electron spin. These operations, combined with electron spin rotations can be used to synthesize any unitary transformation on the coupled electron-nuclear spin system. We discuss how these methods can be used for design of experiments for transfer of polarization from the electron to the nuclear spins.

  10. General classical and quantum-mechanical description of magnetic resonance

    E-Print Network [OSTI]

    Alexander J. Silenko

    2015-08-04

    A general theoretical description of the magnetic resonance is given. General formulas describing a behavior of all components of the polarization vector at the magnetic resonance are derived in the case of an arbitrary initial polarization. The equations obtained are exact on condition that the nonresonance rotating field is neglected. The spin dynamics is also calculated at frequencies far from resonance without neglecting the above-mentioned field. A quantum-mechanical analysis of the spin evolution at the magnetic resonance is fulfilled and the full agreement between the classical and quantum-mechanical approaches is proven. Distinguishing features of magnetic and quasimagnetic resonances for nuclei and particles moving in accelerators and storage rings which include resonances caused by the electric dipole moment are considered.

  11. General classical and quantum-mechanical description of magnetic resonance

    E-Print Network [OSTI]

    Silenko, Alexander J

    2015-01-01

    A general theoretical description of the magnetic resonance is given. General formulas describing a behavior of all components of the polarization vector at the magnetic resonance are derived in the case of an arbitrary initial polarization. The equations obtained are exact on condition that the nonresonance rotating field is neglected. The spin dynamics is also calculated at frequencies far from resonance without neglecting the above-mentioned field. A quantum-mechanical analysis of the spin evolution at the magnetic resonance is fulfilled and the full agreement between the classical and quantum-mechanical approaches is proven. Distinguishing features of magnetic and quasimagnetic resonances for nuclei and particles moving in accelerators and storage rings which include resonances caused by the electric dipole moment are considered.

  12. 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.

    2013-06-01

    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

  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.

    2013-06-01

    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. On the Dramatic Spin-up/Spin-down Torque Reversals in Accreting Pulsars

    E-Print Network [OSTI]

    Robert W. Nelson; Lars Bildsten; Deepto Chakrabarty; Mark H. Finger; Danny T. Koh; Thomas A. Prince; Bradley C. Rubin; D. Mathew Scott; Brian A. Vaughan; Robert B. Wilson

    1997-08-21

    Dramatic torque reversals between spin up and spin down have been observed in half of the persistent X-ray pulsars monitored by the BATSE all-sky monitor on CGRO. Theoretical models developed to explain early pulsar timing data can explain spin down torques via a disk-magnetosphere interaction if the star nearly corotates with the inner accretion disk. To produce the observed BATSE torque reversals, however, these equilibrium models require the disk to alternate between two mass accretion rates, with $\\dot M_{\\pm}$ producing accretion torques of similar magnitude, but always of opposite sign. Moreover, in at least one pulsar (GX 1+4) undergoing secular spin down the neutron star spins down faster during brief ($\\sim 20$ day) hard X-ray flares -- this is opposite the correlation expected from standard theory, assuming BATSE pulsed flux increases with mass accretion rate. The $10$ day to 10 yr intervals between torque reversals in these systems are much longer than any characteristic magnetic or viscous time scale near the inner disk boundary and are more suggestive of a global disk phenomenon. We discuss possible explanations of the observed torque behavior. Despite the preferred sense of rotation defined by the binary orbit, the BATSE observations are surprisingly consistent with an earlier suggestion by Makishima \\etal (1988) for GX~1+4: the disks in these systems somehow alternate between episodes of prograde and retrograde rotation. We are unaware of any mechanism that could produce a stable retrograde disk in a binary undergoing Roche-lobe overflow, but such flip-flop behavior does occur in numerical simulations of wind-fed systems. One possibility is that the disks in some of these binaries are fed by an X-ray excited wind.

  15. Nuclear spin circular dichroism

    SciTech Connect (OSTI)

    Vaara, Juha; Rizzo, Antonio; Kauczor, Joanna; Norman, Patrick; Coriani, Sonia

    2014-04-07

    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.

  16. Ab initio non-relativistic spin dynamics

    SciTech Connect (OSTI)

    Ding, Feizhi; Goings, Joshua J.; Li, Xiaosong; Frisch, Michael J.

    2014-12-07

    Many magnetic materials do not conform to the (anti-)ferromagnetic paradigm where all electronic spins are aligned to a global magnetization axis. Unfortunately, most electronic structure methods cannot describe such materials with noncollinear electron spin on account of formally requiring spin alignment. To overcome this limitation, it is necessary to generalize electronic structure methods and allow each electron spin to rotate freely. Here, we report the development of an ab initio time-dependent non-relativistic two-component spinor (TDN2C), which is a generalization of the time-dependent Hartree-Fock equations. Propagating the TDN2C equations in the time domain allows for the first-principles description of spin dynamics. A numerical tool based on the Hirshfeld partitioning scheme is developed to analyze the time-dependent spin magnetization. In this work, we also introduce the coupling between electron spin and a homogenous magnetic field into the TDN2C framework to simulate the response of the electronic spin degrees of freedom to an external magnetic field. This is illustrated for several model systems, including the spin-frustrated Li{sub 3} molecule. Exact agreement is found between numerical and analytic results for Larmor precession of hydrogen and lithium atoms. The TDN2C method paves the way for the ab initio description of molecular spin transport and spintronics in the time domain.

  17. Fractalization drives crystalline states in a frustrated spin system

    SciTech Connect (OSTI)

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

    2008-01-01

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

  18. NMR evidence for inhomogeneous glassy behavior driven by nematic fluctuations in iron arsenide superconductors

    SciTech Connect (OSTI)

    Dioguardi, A. P.; Lawson, M. M.; Bush, B. T.; Crocker, J.; Shirer, K. R.; Nisson, D. M.; Kissikov, T.; Ran, S.; Bud'ko, S. L.; Canfield, P. C.; Yuan, S.; Kuhns, P. L.; Reyes, A. P.; Grafe, H. -J.; Curro, N. J.

    2015-10-16

    We present 75As nuclear magnetic resonance spin-lattice and spin-spin relaxation rate data in Ba(Fe1–xCox)2As2 and Ba(Fe1–xCux)2As2 as a function of temperature, doping, and magnetic field. The relaxation curves exhibit a broad distribution of relaxation rates, consistent with inhomogeneous glassy behavior up to 100 K. The doping and temperature response of the width of the dynamical heterogeneity is similar to that of the nematic susceptibility measured by elastoresistance measurements. In this study, we argue that quenched random fields which couple to the nematic order give rise to a nematic glass that is reflected in the spin dynamics.

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

    SciTech Connect (OSTI)

    Banerjee, D.; Ganguly, S.; Saha, D.; Adari, R.; Sankaranarayan, S.; Kumar, A.; Aldhaheri, R. W.; Hussain, M. A.; Balamesh, A. S.

    2013-12-09

    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.

  20. 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

  1. Magnetic origin of dielectric transition in BiFeO{sub 3}

    SciTech Connect (OSTI)

    Ray, J.; Biswal, A. K.; Vishwakarma, P. N.; Babu, P. D.; Siruguri, V.

    2014-04-24

    Magnetic relaxation measurements at 5K, 50K and 120K on BiFeO{sub 3} prepared by sol-gel auto combustion method shows stretched -exponential decay. These results shows the two factors viz, cooperative dynamics and rate of dynamics of spin, may be responsible for the low temperature magnetic-glassy behavior, concluded from bifurcation of zero field cooled (ZFC) and field cooled (FC) data of dc magnetization. Temperature dependent dielectric measurement shows a possible phase transition, seen in the dielectric-relaxation time and dielectric constant in the range 200 – 240K. Comparison of dielectric and magnetization data indicates a possibility of magneto-electric coupling.

  2. Spin Glasses and Frustration Cynthia Olson, Chairman Transverse spin freezing in a-FexZr100x

    E-Print Network [OSTI]

    Ryan, Dominic

    Spin Glasses and Frustration Cynthia Olson, Chairman Transverse spin freezing in a-FexZr100x signatures of transverse spin freezing provides a clear confirmation of predictions from numerical models with random isotropic spin freezing and neither net magnetization nor long range order. At lower levels

  3. Time-optimal polarization transfer from an electron spin to a nuclear spin

    E-Print Network [OSTI]

    Haidong Yuan; Robert Zeier; Nikolas Pomplun; Steffen J. Glaser; Navin Khaneja

    2015-09-07

    Polarization transfers from an electron spin to a nuclear spin are essential for various physical tasks, such as dynamic nuclear polarization in nuclear magnetic resonance and quantum state transformations on hybrid electron-nuclear spin systems. We present time-optimal schemes for electron-nuclear polarization transfers which improve on conventional approaches and will have wide applications.

  4. Nanocluster building blocks of artificial square spin ice: Stray-field studies of thermal dynamics

    SciTech Connect (OSTI)

    Pohlit, Merlin Porrati, Fabrizio; Huth, Michael; Müller, Jens

    2015-05-07

    We present measurements of the thermal dynamics of a Co-based single building block of an artificial square spin ice fabricated by focused electron-beam-induced deposition. We employ micro-Hall magnetometry, an ultra-sensitive tool to study the stray field emanating from magnetic nanostructures, as a new technique to access the dynamical properties during the magnetization reversal of the spin-ice nanocluster. The obtained hysteresis loop exhibits distinct steps, displaying a reduction of their “coercive field” with increasing temperature. Therefore, thermally unstable states could be repetitively prepared by relatively simple temperature and field protocols allowing one to investigate the statistics of their switching behavior within experimentally accessible timescales. For a selected switching event, we find a strong reduction of the so-prepared states' “survival time” with increasing temperature and magnetic field. Besides the possibility to control the lifetime of selected switching events at will, we find evidence for a more complex behavior caused by the special spin ice arrangement of the macrospins, i.e., that the magnetic reversal statistically follows distinct “paths” most likely driven by thermal perturbation.

  5. Exploring large coherent spin systems with solid state NMR

    E-Print Network [OSTI]

    Cho, HyungJoon, Ph. D. Massachusetts Institute of Technology

    2005-01-01

    Solid state Nuclear Magnetic Resonance (NMR) allows us to explore a large coherent spin system and provides an ideal test-bed for studying strongly interacting multiple-spin system in a large Hilbert space. In this thesis, ...

  6. Spinning angle optical calibration apparatus

    DOE Patents [OSTI]

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

    1991-01-01

    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.

  7. Spin waves in the (

    SciTech Connect (OSTI)

    Lipscombe, O. J.; Chen, G. F.; Fang, Chen; Perring, T. G.; Abernathy, Douglas L; Christianson, Andrew D; Egami, Takeshi; Wang, Nanlin; Hu, Jiangping; Dai, Pengcheng

    2011-01-01

    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.

  8. Noble gas magnetic resonator

    DOE Patents [OSTI]

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

    2014-04-15

    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.

  9. Squeezing in Multivariate Spin Systems

    E-Print Network [OSTI]

    Swarnamala Sirsi

    2005-09-18

    In contrast to the canonically conjugate variates $q$,$p$ representing the position and momentum of a particle in the phase space distributions, the three Cartesian components, $J_{x}$,$J_{y}$, $J_{z}$ of a spin-$j$ system constitute the mutually non-commuting variates in the quasi-probabilistic spin distributions. It can be shown that a univariate spin distribution is never squeezed and one needs to look into either bivariate or trivariate distributions for signatures of squeezing. Several such distributions result if one considers different characteristic functions or moments based on various correspondence rules. As an example, discrete probability distribution for an arbitrary spin-1 assembly is constructed using Wigner-Weyl and Margenau-Hill correspondence rules. It is also shown that a trivariate spin-1 assembly resulting from the exposure of nucleus with non-zero quadrupole moment to combined electric quadrupole field and dipole magnetic field exhibits squeezing in cerain cases.

  10. Novel bias-field-free spin transfer oscillator

    SciTech Connect (OSTI)

    Windbacher, Thomas Makarov, Alexander; Mahmoudi, Hiwa; Sverdlov, Viktor; Selberherr, Siegfried

    2014-05-07

    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.

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

    E-Print Network [OSTI]

    Hong, Jeongmin

    2009-01-01

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

  12. 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.; Khvalkovskiy, A. V.; Kubota, H.; Fukushima, A.; Yakushiji, K.; Yuasa, S.

    2014-07-14

    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.

  13. Tuning the band structures of a one-dimensional width-modulated magnonic crystal by a transverse magnetic field

    SciTech Connect (OSTI)

    Di, K.; Lim, H. S. Zhang, V. L.; Ng, S. C.; Kuok, M. H.; Nguyen, H. T.; Cottam, M. G.

    2014-02-07

    Theoretical studies, based on three independent techniques, of the band structure of a one-dimensional width-modulated magnonic crystal under a transverse magnetic field are reported. The band diagram is found to display distinct behaviors when the transverse field is either larger or smaller than a critical value. The widths and center positions of bandgaps exhibit unusual non-monotonic and large field-tunability through tilting the direction of magnetization. Some bandgaps can be dynamically switched on and off by simply tuning the strength of such a static field. Finally, the impact of the lowered symmetry of the magnetic ground state on the spin-wave excitation efficiency of an oscillating magnetic field is discussed. Our finding reveals that the magnetization direction plays an important role in tailoring magnonic band structures and hence in the design of dynamic spin-wave switches.

  14. Alternating magnetic anisotropy of Li2(Li1–xTx)N(T=Mn,Fe,Co,andNi)

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

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

    2015-05-11

    Substantial amounts of the transition metals Mn, Fe, Co, and Ni can be substituted for Li in single crystalline Li2(Li1–xTx)N. Isothermal and temperature-dependent magnetization measurements reveal local magnetic moments with magnitudes significantly exceeding the spin-only value. The additional contributions stem from unquenched orbital moments that lead to rare-earth-like behavior of the magnetic properties. Accordingly, extremely large magnetic anisotropies have been found. Most notably, the magnetic anisotropy alternates as easy plane?easy axis?easy plane?easy axis when progressing from T = Mn ? Fe ? Co ? Ni. This behavior can be understood based on a perturbation approach in an analytical, single-ion model.more »As a result, the calculated magnetic anisotropies show surprisingly good agreement with the experiment and capture the basic features observed for the different transition metals.« less

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

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

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

    2015-05-01

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

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

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

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

    2015-05-01

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

  17. Swing switching of spin-torque valves

    E-Print Network [OSTI]

    Tom Dunn; Alex Kamenev

    2012-10-10

    We propose a method for inducing magnetization reversal using an AC spin current polarized perpendicular to the equilibrium magnetization of the free magnetic layer. We show that the critical AC spin current is significantly smaller than the corresponding DC one. The effect is understood as a consequence of the underdamped nature of the spin-torque oscillators. It allows to use the kinetic inertia to overcome the residual energy barrier, rather than suppressing the latter by a large spin current. The effect is similar to a swing which may be set into high amplitude motion by a weak near-resonant push. The optimal AC frequency is identified as the upper bifurcation frequency of the corresponding driven nonlinear oscillator. Together with fast switching times it makes the perpendicular AC method to be the most efficient way to realize spin-torque memory valve.

  18. Cavity cooling of an ensemble spin system

    E-Print Network [OSTI]

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

    2014-02-24

    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.

  19. New method for a continuous determination of the spin tune in storage rings and implications for precision experiments

    E-Print Network [OSTI]

    D. Eversmann; V. Hejny; F. Hinder; A. Kacharava; J. Pretz; F. Rathmann; M. Rosenthal; F. Trinkel; S. Andrianov; W. Augustyniak; Z. Bagdasarian; M. Bai; W. Bernreuther; S. Bertelli; M. Berz; J. Bsaisou; S. Chekmenev; D. Chiladze; G. Ciullo; M. Contalbrigo; J. de Vries; S. Dymov; R. Engels; F. M. Esser; O. Felden; M. Gaisser; R. Gebel; H. Glückler; F. Goldenbaum; K. Grigoryev; D. Grzonka; G. Guidoboni; C. Hanhart; D. Heberling; N. Hempelmann; J. Hetzel; R. Hipple; D. Hölscher; A. Ivanov; V. Kamerdzhiev; B. Kamys; I. Keshelashvili; A. Khoukaz; I. Koop; H-J. Krause; S. Krewald; A. Kulikov; A. Lehrach; P. Lenisa; N. Lomidze; B. Lorentz; P. Maanen; G. Macharashvili; A. Magiera; R. Maier; K. Makino; B. Marianski; D. Mchedlishvili; Ulf-G. Meißner; S. Mey; A. Nass; G. Natour; N. Nikolaev; M. Nioradze; A. Nogga; K. Nowakowski; A. Pesce; D. Prasuhn; J. Ritman; Z. Rudy; A. Saleev; Y. Semertzidis; Y. Senichev; V. Shmakova; A. Silenko; J. Slim; H. Soltner; A. Stahl; R. Stassen; M. Statera; E. Stephenson; H. Stockhorst; H. Straatmann; H. Ströher; M. Tabidze; R. Talman; P. Thörngren Engblom; A. Trzcinski; Yu. Uzikov; Yu. Valdau; E. Valetov; A. Vassiliev; C. Weidemann; C. Wilkin; A. Wirzba; A. Wronska; P. Wüstner; M. Zakrzewska; E. Zaplatin; P. Zupranski; D. Zyuzin

    2015-04-02

    A new method to determine the spin tune is described and tested. In an ideal planar magnetic ring, the spin tune - defined as the number of spin precessions per turn - is given by $\

  20. New method for a continuous determination of the spin tune in storage rings and implications for precision experiments

    E-Print Network [OSTI]

    Eversmann, D; Hinder, F; Kacharava, A; Pretz, J; Rathmann, F; Rosenthal, M; Trinkel, F; Andrianov, S; Augustyniak, W; Bagdasarian, Z; Bai, M; Bernreuther, W; Bertelli, S; Berz, M; Bsaisou, J; Chekmenev, S; Chiladze, D; Ciullo, G; Contalbrigo, M; de Vries, J; Dymov, S; Engels, R; Esser, F M; Felden, O; Gaisser, M; Gebel, R; Glückler, H; Goldenbaum, F; Grigoryev, K; Grzonka, D; Guidoboni, G; Hanhart, C; Heberling, D; Hempelmann, N; Hetzel, J; Hipple, R; Hölscher, D; Ivanov, A; Kamerdzhiev, V; Kamys, B; Keshelashvili, I; Khoukaz, A; Koop, I; Krause, H-J; Krewald, S; Kulikov, A; Lehrach, A; Lenisa, P; Lomidze, N; Lorentz, B; Maanen, P; Macharashvili, G; Magiera, A; Maier, R; Makino, K; Marianski, B; Mchedlishvili, D; Meißner, Ulf-G; Mey, S; Nass, A; Natour, G; Nikolaev, N; Nioradze, M; Nogga, A; Nowakowski, K; Pesce, A; Prasuhn, D; Ritman, J; Rudy, Z; Saleev, A; Semertzidis, Y; Senichev, Y; Shmakova, V; Silenko, A; Slim, J; Soltner, H; Stahl, A; Stassen, R; Statera, M; Stephenson, E; Stockhorst, H; Straatmann, H; Ströher, H; Tabidze, M; Talman, R; Engblom, P Thörngren; Trzcinski, A; Uzikov, Yu; Valdau, Yu; Valetov, E; Vassiliev, A; Weidemann, C; Wilkin, C; Wirzba, A; Wronska, A; Wüstner, P; Zakrzewska, M; Zaplatin, E; Zupranski, P; Zyuzin, D

    2015-01-01

    A new method to determine the spin tune is described and tested. In an ideal planar magnetic ring, the spin tune - defined as the number of spin precessions per turn - is given by $\

  1. 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)

    2014-01-01

    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.

  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)

    2014-05-07

    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. Nuclear magnetic relaxation and diffusion in liquid CHCl?-CDCl? mixtures 

    E-Print Network [OSTI]

    Prevost, R. J

    1965-01-01

    resonant state. A light-oil sample was inserted into the probe as a source of protons in adjusting the magnetic field for resonance. This source was chosen for its short relaxation time when compared to that of chloroform. The longitudinal relaxa- tion.... The viscosities of the CHC1 -CDCl 3 . 3 mixtures are measured for use in the calculations. CHA PTER ZI THEORY Huclear Magnetic Resonance The behavior of free spins in an external magnetic field can be adequately understood from a classical approach...

  4. the centres of the magnetic traps for the two spin species along the z . Furthermore, the desired behaviour of the Rabi frequency can

    E-Print Network [OSTI]

    Lang, Kristine M.

    ., Burt, E. A., Ghrist, R. W., Cornell, E. A. & Wieman, C. E. Production of two overlapping Bose±Einstein con®nement of a Bose±Einstein condensate. Phys. Rev. Lett. 80, 2027±2030 (1998). 3. Stenger, J. et al. Spin domains in ground-state Bose±Einstein condensates. Nature 396, 345±348 (1998). 4. Hall, D. S

  5. 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.; Liu Yang

    2013-08-01

    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.

  6. Magnetic order and heavy fermion behavior in CePd{sub 1+x}Al{sub 6-x}: Synthesis, structure, and physical properties

    SciTech Connect (OSTI)

    Tobash, Paul H., E-mail: ptobash@lanl.go [Materials Physics and Application Division, MPA-10, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Ronning, Filip; Thompson, J.D. [Materials Physics and Application Division, MPA-10, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Bobev, Svilen [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Bauer, Eric D. [Materials Physics and Application Division, MPA-10, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2010-03-15

    The physical properties including magnetic susceptibility, specific heat, and electrical resistivity of single crystals are reported for the compound CePd{sub 1+x}Al{sub 6-x} (x=0.5) which crystallizes in the tetragonal SrAu{sub 2}Ga{sub 5}-type structure (space group P4/mmm). The compound was grown from an excess of molten Al flux from the respective elements and the crystal structure was established from single-crystal X-ray diffraction. Anomalies in the low temperature specific heat C{sub p}(T) and electrical resistivity rho(T) show that the compound undergoes ferromagnetic order at T{sub C}=2.8 K. In the ordered state, CePd{sub 1.5}Al{sub 5.5} displays heavy fermion behavior with a Sommerfeld coefficient of ca. 500 mJ/mol-K{sup 2}. - Graphical abstract: The compound CePd{sub 1+x}Al{sub 6-x} (x=0.5) has been synthesized and structurally characterized by single-crystal X-ray diffraction. The measured physical properties of temperature and field dependent magnetic susceptibility, specific heat, and electrical resistivity suggests that the compound undergoes ferromagnetic order at ca. 2.8 K and further exhibits relatively heavy fermion behavior with a Sommerfeld coefficient of 500 mJ/mol-K2.

  7. Processing optimization and sintering time dependent magnetic and optical behaviors of Aurivillius Bi{sub 5}Ti{sub 3}FeO{sub 15} ceramics

    SciTech Connect (OSTI)

    Chen Guang; Sun Lin; Ren Qing; Xu Wenfei; Yang Jing; Tang Xiaodong; Bai Wei; Duan Chungang; Chu Junhao; Wu Jing; Meng Xiangjian

    2013-01-21

    Aurivillius Bi{sub 5}Ti{sub 3}FeO{sub 15} (BTF) ceramics were synthesized using the conventional solid state reaction method by optimizing excess of Bi{sub 2}O{sub 3} and sintering time. Their structures, magnetic, and optical properties were investigated in detail. The optimum process to sinter pure Aurivillius BTF ceramics was confirmed to be 3 wt. % excess Bi{sub 2}O{sub 3} to compensate the Bi volatilization at 1050 Degree-Sign C for 240 min (BTF-240M). The microstructure and crystalline structure of the BTF ceramics had little dependence on the sintering time from the x-ray diffraction (XRD) and scanning electron microscopic data. Nevertheless, the magnetic and optical properties were closely related with the sintering time. The overall magnetic behavior of these BTF ceramics was superparamagnetic (SPM), whereas there were unambiguous clues for the existence of antiferromagnetic (AFM) interactions. However, whether the SPM behavior was intrinsic or arised from a tiny amount of spinel Fe{sub 3}O{sub 4} impurity phase cannot be thoroughly ruled out in the XRD detection limit in the present stage. The AFM interactions were weakened upon extending the sintering time. The effective magnetic moment ({mu}{sub eff}), however, demonstrated different dependency on the sintering time. It increased with the sintering time from 80 min to 240 min, and then dropped with further extending the sintering time. Compared with other BTF ceramics, the BTF-240M ceramic showed the highest values of the refractive index n and real part {epsilon}{sub 1}, as well as the lowest ones of the extinction coefficient k and imagine part {epsilon}{sub 2} in whole photon energy range. Finally, a direct inter-band transition was confirmed for these BTF ceramics and optical energy band gaps were determined to be about 3.08, 3.18, and 3.39 eV for 80 min, 150 min, and 240 min sintered BTF ceramics, respectively, yet abnormal optical behavior was observed in BTF-360M ceramic.

  8. ARPES Provides Direct Evidence of Spin-Wave Coupling

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

    ARPES Provides Direct Evidence of Spin-Wave Coupling Print The electronic properties of a metal are determined by the dynamical behavior of its conduction electrons. Conventional...

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

    SciTech Connect (OSTI)

    Ramos, J. P.; Apel, V. M.; Foa Torres, L. E. F.; Orellana, P. A.

    2014-03-28

    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.

  10. Coherent, Mechanical Control of a Single Electronic Spin Sungkun Hong,,

    E-Print Network [OSTI]

    Yacoby, Amir

    Coherent, Mechanical Control of a Single Electronic Spin Sungkun Hong,, Michael S. Grinolds coherent quantum control of a single spin driven by the motion of a mechanical resonator. The motion of a mechanical resonator is magnetically coupled to the electronic spin of a single nitrogen-vacancy center

  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. Nonmagnetic semiconductor spin transistor K. C. Hall,a)

    E-Print Network [OSTI]

    Flatte, Michael E.

    as a spin valve, or a magnetic field sensor. © 2003 American Institute of Physics. DOI: 10 there is a natural choice of quantization axis for spin along which precessional spin re- laxation is suppressed.12 of an external electric field to a symmetric InAs two-dimensional electron gas 2DEG between the in- jector

  13. Magnetic properties of double perovskite La2BMnO6 (B = Ni or Co) nanoparticles

    SciTech Connect (OSTI)

    Mao, Yuanbing; Parsons, Jason; McCloy, John S.

    2013-03-31

    Double perovskite La2BMnO6 (B = Ni and Co) nanoparticles with average particle size of ~50 nm were synthesized using a facile, environmentally friendly, scalable molten-salt reaction at 700 °C in air. Their structural and morphological properties were characterized by x-ray diffraction and transmission electron microscopy. Magnetic properties were evaluated using dc magnetic M-T and M-H, and ac magnetic susceptibility versus frequency, temperature, and field. The magnetization curve shows a paramagnetic-ferromagnetic transition at TC ~275 and 220 K for La2NiMnO6 (LNMO) and La2CoMnO6 (LCMO) nanoparticles, respectively. ac susceptibility revealed that the LCMO had a single magnetic transition indicative of Co2+-O2--Mn4+ ordering, whereas the LNMO showed more complex magnetic behavior suggesting a re-entrant spin glass.

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

    SciTech Connect (OSTI)

    Dhaka, Kapil Trivedi, Ravi Bandyopadhyay, Debashis

    2014-04-24

    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.

  15. Magnetic hardening of Ce1+xFe11–yCoyTi with ThMn12 structure by melt spinning

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

    Zhou, Chen; Sun, Kewei; Pinkerton, Frederick E.; Kramer, M. J.

    2015-04-15

    A recent study on the intrinsic magnetic properties of CeFe11–yCoyTi has revealed that substituting one Co for Fe retains the favorable magnetocrystalline anisotropy Ha found in the ternary Fe end member, while enhancing the Curie temperature Tc and saturation magnetization 4?Ms. These findings warrant further optimization around Co substitution y = 1 to try to exploit the hard magnetic properties of these Ce-based magnets. Both Ce and Co concentrations in Ce1+xFe11–yCoyTi have been optimized in the range of x = 0 – 0.2 and y = 0 –1.5. It was found that Co substitution effectively enhances all hard magnetic properties,more »although the values are still lower than those predicted from the intrinsic magnetic properties. Specifically, Tc increases from 210 °C to 285 – 350 °C; 4?M19 (magnetization at 19 kOe) from 8.9 kG to 10.5 – 11.5 kG, remanence Br from 3.1 kG to 4.1 – 4.5 kG, and most importantly, Hci from 1.1 kOe to 1.5 kOe. As a result, the room temperature energy product (BH)max has been increased by over 100% from 0.7 MGOe in Ce1.1Fe11Ti to 1.5 MGOe in Ce1.05Fe9.75Co1.25Ti. Microscopy analysis indicates that the addition of Co refines the grain size and promotes chemical homogeneity at the microscopic scale. As a result, the beneficial effect of Co on the microstructure contributes to the improved hard magnetic properties.« less

  16. All-electrical time-resolved spin generation and spin manipulation in n-InGaAs

    SciTech Connect (OSTI)

    Stepanov, I.; Kuhlen, S.; Ersfeld, M.; Beschoten, B., E-mail: bernd.beschoten@physik.rwth-aachen.de [2nd Institute of Physics and JARA-FIT, RWTH Aachen University, D-52074 Aachen (Germany); Lepsa, M. [Peter Grünberg Institut (PGI-9) and JARA-FIT, Forschungszentrum Jülich GmbH, D-52425 Jülich (Germany)

    2014-02-10

    We demonstrate all-electrical spin generation and subsequent manipulation by two successive electric field pulses in an n-InGaAs heterostructure in a time-resolved experiment at zero external magnetic field. The first electric field pulse along the [11{sup ¯}0] crystal axis creates a current-induced spin polarization (CISP) which is oriented in the plane of the sample. The subsequent electric field pulse along [110] generates a perpendicular magnetic field pulse leading to a coherent precession of this spin polarization with 2-dimensional electrical control over the final spin orientation. Spin precession is probed by time-resolved Faraday rotation. We determine the build-up time of CISP during the first field pulse and extract the spin dephasing time and internal magnetic field strength during the spin manipulation pulse.

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

    SciTech Connect (OSTI)

    Wang, Qi; Zhang, Huaiwu Tang, Xiaoli; Bai, Feiming; Zhong, Zhiyong; Fangohr, Hans

    2014-09-15

    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.

  18. Classical gravitational spin-spin interaction

    E-Print Network [OSTI]

    W. B. Bonnor

    2002-01-30

    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.

  19. Enhanced magnetic moment and conductive behavior in NiFe{sub 2}O{sub 4} spinel ultrathin films

    SciTech Connect (OSTI)

    Lueders, Ulrike [Institut de Ciencia de Materials de Barcelona, CSIC, Campus de la UAB, 08193 Bellaterra, Catalunya (Spain); LPMC-FRE2686 CNRS-ONERA, 2 avenue Edouard Belin, 31400 Toulouse (France); Bibes, Manuel [Unite Mixte de Physique THALES/CNRS, Domaine de Corbeville, 91404 Orsay (France); Institut d'Electronique Fondamentale, Universite Paris-Sud, 91405 Orsay (France); Bobo, Jean-Francois [LPMC-FRE2686 CNRS-ONERA, 2 avenue Edouard Belin, 31400 Toulouse (France); Cantoni, Matteo; Bertacco, Riccardo [INFM and L-NESS, Dipartimento di Fisica del Politecnico di Milano, via Anzani 52, 22100 Como (Italy); Fontcuberta, Josep [Institut de Ciencia de Materials de Barcelona, CSIC, Campus de la UAB, 08193 Bellaterra, Catalunya (Spain)

    2005-04-01

    Bulk NiFe{sub 2}O{sub 4} is an insulating ferrimagnet. Here, we report on the epitaxial growth of spinel NiFe{sub 2}O{sub 4} ultrathin films onto SrTiO{sub 3} single crystals. We will show that--under appropriate growth conditions--epitaxial stabilization leads to the formation of a spinel phase with magnetic and electrical properties that radically differ from those of the bulk material: an enhanced magnetic moment (M{sub S})--about 250% larger--and a metallic character. A systematic study of the thickness dependence of M{sub S} allows us to conclude that its enhanced value is due to an anomalous distribution of the Fe and Ni cations among the A and B sites of the spinel structure resulting from the off-equilibrium growth conditions and to interface effects. The relevance of these findings for spinel- and, more generally, oxide-based heterostructures is discussed. We will argue that this novel material could be an alternative ferromagetic-metallic electrode in magnetic tunnel junctions.

  20. High-spin nuclear spectroscopy

    SciTech Connect (OSTI)

    Diamond, R.M.

    1986-07-01

    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. 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)

    2014-05-07

    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.

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

    SciTech Connect (OSTI)

    Fomina, Irina; Dobrokhotova, Zhanna; Aleksandrov, Grygory; Emelina, Anna; Bykov, Mikhail; Bogomyakov, Artem; Puntus, Lada; Novotortsev, Vladimir; Eremenko, Igor

    2012-01-15

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

  3. Spin ejector

    DOE Patents [OSTI]

    Andersen, John A. (Alburquerque, NM); Flanigan, John J. (Alburquerque, NM); Kindley, Robert J. (Alburquerque, NM)

    1978-01-01

    The disclosure relates to an apparatus for spin ejecting a body having a flat plate base containing bosses. The apparatus has a base plate and a main ejection shaft extending perpendicularly from the base plate. A compressible cylindrical spring is disposed about the shaft. Bearings are located between the shaft and the spring. A housing containing a helical aperture releasably engages the base plate and surrounds the shaft bearings and the spring. A piston having an aperture follower disposed in the housing aperture is seated on the spring and is guided by the shaft and the aperture. The spring is compressed and when released causes the piston to spin eject the body.

  4. Tidal deformations of a spinning compact object

    E-Print Network [OSTI]

    Pani, Paolo; Maselli, Andrea; Ferrari, Valeria

    2015-01-01

    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 mom...

  5. Effects of Cr doping on the magnetic properties of multiferroic YMnO{sub 3}

    SciTech Connect (OSTI)

    Han, Tai-Chun Wu, I-Chu; Hsu, Hsin-Kai

    2014-05-07

    We have synthesized a series of YMn{sub 1?x}Cr{sub x}O{sub 3} (0???x???0.1) samples and study the effect of Cr-doping on their magnetic properties. The magnetic characterization indicates that with increasing Cr-content up to 0.1, the antiferromagnetic (AFM) transition temperature increases from 73 to 89?K. Our experiment results also indicate that the Cr-doped samples exhibit the characteristics of spin-glass state at low temperature. Moreover, the magnetic hysteresis curves of the doped samples show a weak ferromagnetic (FM) behavior. It is found that the spin-glass state of the Cr-doped samples is due to the competition between AFM superexchange and FM double-exchange interaction, induced by the Cr doping.

  6. Jahn-Teller versus quantum effects in the spin-orbital material LuVO3

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

    Skoulatos, M.; Toth, S.; Roessli, B.; Enderle, M.; Habicht, K.; Sheptyakov, D.; Cervellino, A.; Freeman, P. G.; Reehuis, M.; Stunault, A.; et al

    2015-04-13

    In this article, we report on combined neutron and resonant x-ray scattering results, identifying the nature of the spin-orbital ground state and magnetic excitations in LuVO3 as driven by the orbital parameter. In particular, we distinguish between models based on orbital-Peierls dimerization, taken as a signature of quantum effects in orbitals, and Jahn-Teller distortions, in favor of the latter. In order to solve this long-standing puzzle, polarized neutron beams were employed as a prerequisite in order to solve details of the magnetic structure, which allowed quantitative intensity analysis of extended magnetic-excitation data sets. The results of this detailed study enabledmore »us to draw definite conclusions about the classical versus quantum behavior of orbitals in this system and to discard the previous claims about quantum effects dominating the orbital physics of LuVO3 and similar systems.« less

  7. Dynamic selective switching in antiferromagnetically-coupled bilayers close to the spin reorientation transition

    SciTech Connect (OSTI)

    Fernández-Pacheco, A., E-mail: af457@cam.ac.uk; Mansell, R.; Petit, D.; Lee, J. H.; Cowburn, R. P. [Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Ummelen, F. C.; Swagten, H. J. M. [Department of Applied Physics, Center for NanoMaterials, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)

    2014-09-01

    We have designed a bilayer synthetic antiferromagnet where the order of layer reversal can be selected by varying the sweep rate of the applied magnetic field. The system is formed by two ultra-thin ferromagnetic layers with different proximities to the spin reorientation transition, coupled antiferromagnetically using Ruderman-Kittel-Kasuya-Yosida interactions. The different dynamic magnetic reversal behavior of both layers produces a crossover in their switching fields for field rates in the kOe/s range. This effect is due to the different effective anisotropy of both layers, added to an appropriate asymmetric antiferromagnetic coupling between them. Field-rate controlled selective switching of perpendicular magnetic anisotropy layers as shown here can be exploited in sensing and memory applications.

  8. Motional Spin Relaxation in Large Electric Fields

    E-Print Network [OSTI]

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

    2008-07-02

    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. Controlling spin relaxation with a cavity

    E-Print Network [OSTI]

    A. Bienfait; J. J. Pla; Y. Kubo; X. Zhou; M. Stern; C. C. Lo; C. D. Weis; T. Schenkel; D. Vion; D. Esteve; J. J. L. Morton; P. Bertet

    2015-08-27

    Spontaneous emission of radiation is one of the fundamental mechanisms by which an excited quantum system returns to equilibrium. For spins, however, spontaneous emission is generally negligible compared to other non-radiative relaxation processes because of the weak coupling between the magnetic dipole and the electromagnetic field. In 1946, Purcell realized that the spontaneous emission rate can be strongly enhanced by placing the quantum system in a resonant cavity -an effect which has since been used extensively to control the lifetime of atoms and semiconducting heterostructures coupled to microwave or optical cavities, underpinning single-photon sources. Here we report the first application of these ideas to spins in solids. By coupling donor spins in silicon to a superconducting microwave cavity of high quality factor and small mode volume, we reach for the first time the regime where spontaneous emission constitutes the dominant spin relaxation mechanism. The relaxation rate is increased by three orders of magnitude when the spins are tuned to the cavity resonance, showing that energy relaxation can be engineered and controlled on-demand. Our results provide a novel and general way to initialise spin systems into their ground state, with applications in magnetic resonance and quantum information processing. They also demonstrate that, contrary to popular belief, the coupling between the magnetic dipole of a spin and the electromagnetic field can be enhanced up to the point where quantum fluctuations have a dramatic effect on the spin dynamics; as such our work represents an important step towards the coherent magnetic coupling of individual spins to microwave photons.

  10. Electrical Spin Injection and Detection in Ge Nanowires and Topological Insulators

    E-Print Network [OSTI]

    Tang, Jianshi

    2014-01-01

    L. -J. Chen, K. L. Wang, “Electrical Spin Injection andJ. Chen, K. L. Wang, “Electrical Probing of Magnetic PhaseM.P. & Jansen, R. Electrical Creation of Spin Polarization

  11. Interference fringes of m=0 spin states under the Majorana transition caused by rapid half-rotation of a magnetic field

    SciTech Connect (OSTI)

    Takahashi, Atsushi; Morinaga, Atsuo [Department of Physics, Faculty of Science and Technology, Tokyo University of Science, Yamazaki, Noda-shi, Chiba 278-8510 (Japan)

    2010-04-15

    The phase shift and visibility of fringes in the Ramsey atom interferometer composed of the |F=1,m{sub F}=0> and |F=2,m{sub F}=0> states were examined systematically for rapid half-rotation of the magnetic field. It was verified that the phase shifts by {pi} rad in the adiabatic regime, but it does not shift from the original one in the nonadiabatic regime. These results support Robbins and Berry's claim [J. M. Robbins and M. V. Berry, J. Phys. A 27, L435 (1994)]. The fact that the interference fringes disappear in the intermediate regime and reappear in the nonadiabatic regime can be explained by the Majorana transition caused by a rapid reverse of the magnetic field.

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

    SciTech Connect (OSTI)

    Ye, L. Gopman, D. B.; Rehm, L.; Backes, D.; Wolf, G.; Kent, A. D.; Ohki, T.; Kirichenko, A. F.; Vernik, I. V.; Mukhanov, O. A.

    2014-05-07

    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.

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

    E-Print Network [OSTI]

    Boris V. Fine

    2004-08-10

    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.''

  14. 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.

    2012-01-01

    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.

  15. Tunneling magnetoresistance phenomenon utilizing graphene magnet electrode

    SciTech Connect (OSTI)

    Hashimoto, T.; Kamikawa, S.; Haruyama, J.; Soriano, D.; Pedersen, J. G.; Roche, S.

    2014-11-03

    Using magnetic rare-metals for spintronic devices is facing serious problems for the environmental contamination and the limited material-resource. In contrast, by fabricating ferromagnetic graphene nanopore arrays (FGNPAs) consisting of honeycomb-like array of hexagonal nanopores with hydrogen-terminated zigzag-type atomic structure edges, we reported observation of polarized electron spins spontaneously driven from the pore edge states, resulting in rare-metal-free flat-energy-band ferromagnetism. Here, we demonstrate observation of tunneling magnetoresistance (TMR) behaviors on the junction of cobalt/SiO{sub 2}/FGNPA electrode, serving as a prototype structure for future rare-metal free TMR devices using magnetic graphene electrodes. Gradual change in TMR ratios is observed across zero-magnetic field, arising from specified alignment between pore-edge- and cobalt-spins. The TMR ratios can be controlled by applying back-gate voltage and by modulating interpore distance. Annealing the SiO{sub 2}/FGNPA junction also drastically enhances TMR ratios up to ?100%.

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

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

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

    2015-01-06

    We report measurements and theoretical analysis of resonant spin tunneling in randomly oriented nanospheres of a molecular magnet. Amorphous nanospheres of Mn?? acetate have been fabricated and characterized by chemical, infrared, TEM, X-ray, and magnetic methods. Magnetic measurements have revealed sharp tunneling peaks in the field derivative of the magnetization that occur at the typical resonant field values for the Mn?? acetate crystal in the field parallel to the easy axis.Theoretical analysis is provided that explains these observations. We argue that resonant spin tunneling in a molecular magnet can be established in a powder sample, without the need for amore »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.« less

  17. 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)

    2015-01-01

    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.

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

    E-Print Network [OSTI]

    V. G. Baryshevsky

    2006-03-23

    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.

  19. Intrinsic Spin-Orbit Interaction in Graphene

    E-Print Network [OSTI]

    B. S. Kandemir

    2012-05-03

    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.

  20. Voltage-Controlled Magnetic Dynamics in Nanoscale Magnetic Tunnel Junctions

    E-Print Network [OSTI]

    Alzate Vinasco, Juan Guillermo

    2014-01-01

    Amiri, “Low-Power Nonvolatile Spintronic Memory: STT-RAM andMagnetic Anisotropy in Spintronic Devices," SPIN, vol. 02,I. A. Young, "Benchmarking spintronic logic devices based on

  1. Ginzburg-Landau theory for skyrmions in inversion-symmetric magnets with competing interactions

    E-Print Network [OSTI]

    Shi-Zeng Lin; Satoru Hayami

    2015-12-15

    Magnetic skyrmions have attracted considerable attention recently for their huge potential in spintronic applications. Generally skyrmions are big compared to the atomic lattice constant, which allows for the Ginzburg-Landau type description in the continuum limit. Such a description successfully captures the main experimental observations on skyrmions in B20 compound without inversion symmetry. Skyrmions can also exist in inversion-symmetric magnets with competing interactions. Here we derive a general Ginzburg-Landau theory for skyrmions in these magnets valid in the long wavelength limit. We study the unusual static and dynamical properties of skyrmions based on the derived Ginzburg-Landau theory. We show that an easy axis spin anisotropy is sufficient to stabilize a skyrmion lattice. Interestingly, the skyrmion in inversion-symmetric magnets has a new internal degree of freedom associated with the rotation of helicity, i.e. the "spin" of the skyrmion as a particle, in addition to the usual translational motion of skyrmions (orbital motion). The orbital and spin degree of freedoms of an individual skyrmion can couple to each other, and give rise to unusual behavior that is absent for the skyrmions stabilized by the Dzyaloshinskii-Moriya interaction. The derived Ginzburg-Landau theory provides a convenient and general framework to discuss skyrmion physics and will facilitate the search for skyrmions in inversion-symmetric magnets.

  2. Quantum spin coherence in halogen-modified Cr$_7$Ni molecular nanomagnets

    E-Print Network [OSTI]

    Danielle Kaminski; Amy L. Webber; Christopher J. Wedge; Junjie Liu; Grigore A. Timco; Inigo J. Vitorica-Yrezabal; Eric J. L. McInnes; Richard E. P. Winpenny; Arzhang Ardavan

    2014-10-30

    Among the factors determining the quantum coherence of the spin in molecular magnets is the presence and the nature of nuclear spins in the molecule. We have explored modifying the nuclear spin environment in Cr$_7$Ni-based molecular nanomagnets by replacing hydrogen atoms with deuterium or the halogen atoms, fluorine or chlorine. We find that the spin coherence, studied at low temperatures by pulsed electron spin resonance, is modified by a range of factors, including nuclear spin and magnetic moment, changes in dynamics owing to nuclear mass, and molecular morphology changes.

  3. Demand Response Spinning Reserve Demonstration

    E-Print Network [OSTI]

    2007-01-01

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

  4. 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)

    2014-08-21

    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.

  5. Electrical Spin Injection and Detection in Ge Nanowires and Topological Insulators

    E-Print Network [OSTI]

    Tang, Jianshi

    2014-01-01

    K. Future Perspectives for Spintronic Devices. J. Phys. D:Ferromagnetic Mn 5 Ge 3 for Spintronic Applications. Phys.Magnetic Anisotropy in Spintronic Devices. Spin 02,

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

    SciTech Connect (OSTI)

    Wen, Hua; Amamou, Walid; Zhu, Tiancong; Luo, Yunqiu; Kawakami, Roland K.

    2014-05-07

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

  7. Spin Glasses: Old and New Complexity

    SciTech Connect (OSTI)

    Stein, D. L.

    2011-09-22

    Spin glasses are disordered magnetic systems that exhibit a variety of properties that are characteristic of 'complex systems'. After a brief review of the systems themselves, I will discuss how spin glass concepts have found use in and, in some cases, further advanced areas such as computer science, biology, and other fields: what one might term 'old complexity'. I will then turn to a discussion of more recent concepts and ideas that have flowed from studies of spin glasses, and using these introduce a proposal for a kind of 'new complexity'.

  8. Spin-Spin Coupling in the Solar System

    E-Print Network [OSTI]

    Batygin, Konstantin

    2015-01-01

    The richness of dynamical behavior exhibited by the rotational states of various solar system objects has driven significant advances in the theoretical understanding of their evolutionary histories. An important factor that determines whether a given object is prone to exhibiting non-trivial rotational evolution is the extent to which such an object can maintain a permanent aspheroidal shape, meaning that exotic behavior is far more common among the small body populations of the solar system. Gravitationally bound binary objects constitute a substantial fraction of asteroidal and TNO populations, comprising systems of triaxial satellites that orbit permanently deformed central bodies. In this work, we explore the rotational evolution of such systems with specific emphasis on quadrupole-quadrupole interactions, and show that for closely orbiting, highly deformed objects, both prograde and retrograde spin-spin resonances naturally arise. Subsequently, we derive capture probabilities for leading order commensur...

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

    E-Print Network [OSTI]

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

    2012-08-02

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

  10. Neutrino electromagnetic properties: new approach to oscillations in magnetic fields

    E-Print Network [OSTI]

    Dmitriev, Alexander; Studenikin, Alexander

    2015-01-01

    Several new and interesting aspects of neutrino oscillations in a magnetic field are considered: 1) We develop a standard usually used approach to the neutrino spin oscillations in the neutrino mass basis and obtain the effective neutrino spin (and "spin-mass") oscillation Hamiltonian that can be used for description of the neutrino oscillations between different pairs of neutrino states with different masses and helicities; 2) We derive the exact solution of the Dirac equation for a massive neutrino with nonzero magnetic moment in the presence of a constant transversal magnetic field that is rotating along the direction of the neutrino propagation (the twisting magnetic field) and on the basis of the obtained energy spectrum the neutrino spin oscillation effective Hamiltonian is derive; 3) We develop a new approach to neutrino spin oscillations that is based on the description of the neutrino spin states with the corresponding spin operator that commutes with the neutrino dynamics Hamiltonian in the magnetic...

  11. Controllable spin polarization and spin filtering in a zigzag silicene nanoribbon

    SciTech Connect (OSTI)

    Farokhnezhad, Mohsen Esmaeilzadeh, Mahdi Pournaghavi, Nezhat; Ahmadi, Somaieh

    2015-05-07

    Using non-equilibrium Green's function, we study the spin-dependent electron transport properties in a zigzag silicene nanoribbon. To produce and control spin polarization, it is assumed that two ferromagnetic strips are deposited on the both edges of the silicene nanoribbon and an electric field is perpendicularly applied to the nanoribbon plane. The spin polarization is studied for both parallel and anti-parallel configurations of exchange magnetic fields induced by the ferromagnetic strips. We find that complete spin polarization can take place in the presence of perpendicular electric field for anti-parallel configuration and the nanoribbon can work as a perfect spin filter. The spin direction of transmitted electrons can be easily changed from up to down and vice versa by reversing the electric field direction. For parallel configuration, perfect spin filtering can occur even in the absence of electric field. In this case, the spin direction can be changed by changing the electron energy. Finally, we investigate the effects of nonmagnetic Anderson disorder on spin dependent conductance and find that the perfect spin filtering properties of nanoribbon are destroyed by strong disorder, but the nanoribbon retains these properties in the presence of weak disorder.

  12. arXiv:1101.3277v1[cond-mat.mes-hall]17Jan2011 Quasilinear spin voltage profiles in spin thermoelectrics

    E-Print Network [OSTI]

    Nunner, Tamara

    of this emerging field were the recent observations of the spin Seebeck effect in ferro- magnets [4­6], where Seebeck effect also raises theoretical puzzles. Remarkably, the spin chemical potential is observed with paramagnetic impurities. In some cases, conservation laws, e.g., for a combination of spin and heat currents

  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. PUBLISHED ONLINE: 12 JUNE 2011 | DOI: 10.1038/NMAT3046 Giant enhancement of spin accumulation and

    E-Print Network [OSTI]

    Otani, Yoshichika

    spin current for potential spintronic application. However, the spin-valve voltage, which determines junction is a building block of spintronic devices such as read heads for magnetic recording and memory a large pure spin current as well as a large spin accumulation for advancement of spintronic devices using

  15. Long-lived states with well-defined spins in spin-$1/2$ homogeneous Bose gases

    E-Print Network [OSTI]

    Yurovsky, Vladimir A

    2015-01-01

    Many-body eigenfunctions of the total spin operator can be constructed from the spin and spatial wavefunctions with non-trivial permutation symmetries. Spin-dependent interactions can lead to relaxation of the spin eigenstates to the thermal equilibrium. The relaxation rate is evaluated here for two- and three-dimensional gases using the chaotic behavior of the thermally-equilibrium spatial state. Dependence of the rate on the total spin and its projection is separated into a factor, which is independent of the gas dimensionality, temperature, and density. This factor can be controlled by a Feshbach resonance, leading to suppression of the relaxation rate by several orders of magnitude.

  16. Decoherence of transported spin in multichannel spin-orbit coupled spintronic devices: Scattering approach to spin density matrix from the ballistic to the localized regime

    E-Print Network [OSTI]

    Branislav K. Nikolic; Satofumi Souma

    2005-03-17

    By viewing current in the detecting lead of a spintronic device as being an ensemble of flowing spins corresponding to a mixed quantum state, where each spin itself is generally described by an improper mixture generated during the transport where it couples to other degrees of freedom due to spin-orbit (SO) interactions or inhomogeneous magnetic fields, we introduce the spin density operator associated with such current expressed in terms of the spin-resolved Landauer transmission matrix of the device. This formalism, which provides complete description of coupled spin-charge quantum transport in open finite-size systems attached to external probes, is employed to understand how initially injected pure spin states, comprising fully spin-polarized current, evolve into the mixed ones corresponding to partially polarized current. We analyze particular routes that diminish spin coherence (signified by decay of the off-diagonal elements of the current spin density matrix) in two-dimensional electron gas-based devices due to the interplay of the Rashba and/or Dresselhaus SO coupling and: (i) scattering at the boundaries or lead-wire interface in ballistic semiconductor nanowires; or (ii) spin-independent scattering off static impurities in both weakly and strongly localized disordered nanowires. The physical interpretation of spin decoherence in the course of multichannel quantum transport in terms of the entanglement of spin to an effectively zero-temperature ``environment'' composed of more than one open orbital conducting channels offers insight into some of the key challenges for spintronics: controlling decoherence of transported spins and emergence of partially coherent spin states in all-electrical spin manipulation schemes based on the SO interactions in realistic semiconductor structures.

  17. 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)

    2013-08-14

    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.

  18. Physical Background OfPhysical Background Of Nuclear Magnetic ResonanceNuclear Magnetic Resonance

    E-Print Network [OSTI]

    Olszewski Jr., Edward A.

    Physical Background OfPhysical Background Of Nuclear Magnetic ResonanceNuclear Magnetic Resonance SpectroscopySpectroscopy Michael McClellan Spring 2009 Department of Physics and Physical Oceanography Theoretically the nucleus can have any of these allowed spins #12;General Characteristics of Nuclear Spin

  19. Tidal deformations of a spinning compact object

    E-Print Network [OSTI]

    Paolo Pani; Leonardo Gualtieri; Andrea Maselli; Valeria Ferrari

    2015-06-30

    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.

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

    SciTech Connect (OSTI)

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

    2014-04-24

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

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

    E-Print Network [OSTI]

    Aparajita Das; Sreeparna Bhadra; Sonali Saha

    2015-03-30

    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. 2007 Nature Publishing Group Nuclear magnetic resonance imaging

    E-Print Network [OSTI]

    Leonardo, Degiorgi

    to sense the magnetic force generated between the tip and spins in a sample. Magnetic resonance is used for the present work is the development of magnetic tips that generate magnetic field gradients as high as 1 of the technique on a patterned CaF2 test object. Unlike the permanent magnet tips previously used for

  3. Optical detection of spin-filter effect for electron spin polarimetry

    SciTech Connect (OSTI)

    Li, X.; Majee, S.; Lampel, G.; Lassailly, Y.; Paget, D.; Peretti, J.; Tereshchenko, O. E.

    2014-08-04

    We have monitored the cathodoluminescence (CL) emitted upon injection of free electrons into a hybrid structure consisting of a thin magnetic Fe layer deposited on a p-GaAs substrate, in which InGaAs quantum wells are embedded. Electrons transmitted through the unbiased metal/semiconductor junction recombine radiatively in the quantum wells. Because of the electron spin-filtering across the Fe/GaAs structure, the CL intensity, collected from the backside, is found to depend on the relative orientation between the injected electronic spin polarization and the Fe layer magnetization. The spin asymmetry of the CL intensity in such junction provides a compact optical method for measuring spin polarization of free electrons beams or of hot electrons in solid-state devices.

  4. Non-Abelian gauge field effects and its relevance to spinning particle dynamics in the technology of spintronics

    E-Print Network [OSTI]

    S. G. Tan; M. B. A. Jalil; X. -J. Liu; T. Fujita

    2007-11-14

    We describe formally the precession of spin vector about the k-space effective magnetic field in condensed matter system with spin orbital effects as constituting a local transformation of the electron wavefunction which necessarily invokes the SU(2) transformation rule to ensure covariance. We showed a "no-precession" condition as pre-requisite for the spin gauge field to exert its influence on spin particle motion. The effects of the spin gauge field on spin particle motion were shown to be consistent in both classical and quantum pictures, which hence should underpin theoretical explanations for important effects in anomalous Hall, spin Hall, spin torque, optical Magnus, geometric quantum computation.

  5. Superconducting magnet for nuclei orientation 

    E-Print Network [OSTI]

    Wang, Fa-Chung

    1968-01-01

    hyperfine coupling (hfs) of the form I S between the nuclear spin and. the electron spin. In this method. , one applies only a sufficient external f1eld (H/T ~ 10 Oe/ K) on a paramagnet1c crystal to polarize the electron spin, which in turn orient... the nuclear spin through hfs. Th1s method thus requires three things: a sufficiently large external magnetic f1eld, a very low temperature, and. a paramagnetic orystal with strong hyperiine coupling. The first sample we choose 1s an holm1um (Ho ) 165...

  6. Novel nuclear magnetic resonance techniques for studying biological molecules

    E-Print Network [OSTI]

    Laws, David D.

    2010-01-01

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

  7. All-electrical manipulation of magnetization dynamics in a ferromagnet...

    Office of Scientific and Technical Information (OSTI)

    All-electrical manipulation of magnetization dynamics in a ferromagnet by antiferromagnets with anisotropic spin Hall effects Citation Details In-Document Search This content will...

  8. Beta (?) tungsten thin films: Structure, electron transport, and giant spin Hall effect

    SciTech Connect (OSTI)

    Hao, Qiang; Chen, Wenzhe; Xiao, Gang

    2015-05-04

    We use a simple magnetron sputtering process to fabricate beta (?) tungsten thin films, which are capable of generating giant spin Hall effect. As-deposited thin films are always in the metastable ?-W phase from 3.0 to 26.7?nm. The ?-W phase remains intact below a critical thickness of 22.1?nm even after magnetic thermal annealing at 280?°C, which is required to induce perpendicular magnetic anisotropy (PMA) in a layered structure of ?-W/Co{sub 40}Fe{sub 40}B{sub 20}/MgO. Intensive annealing transforms the thicker films (>22.1?nm) into the stable ?-W phase. We analyze the structure and grain size of both ?- and ?-W thin films. Electron transport in terms of resistivity and normal Hall effect is studied over a broad temperature range of 10?K to at least 300?K on all samples. Very low switching current densities are achieved in ?-W/Co{sub 40}Fe{sub 40}B{sub 20}/MgO with PMA. These basic properties reveal useful behaviors in ?-W thin films, making them technologically promising for spintronic magnetic random access memories and spin-logic devices.

  9. Magnetization reversal induced by in-plane current in Ta/CoFeB/MgO structures with perpendicular magnetic easy axis

    SciTech Connect (OSTI)

    Zhang, C.; Yamanouchi, M. Ikeda, S.; Sato, H.; Fukami, S.; Matsukura, F.; Ohno, H.

    2014-05-07

    We investigate in-plane current-induced magnetization reversal under an in-plane magnetic field in Hall bar shaped devices composed of Ta/CoFeB/MgO structures with perpendicular magnetic easy axis. The observed relationship between the directions of current and magnetization switching and Ta thickness dependence of magnetization switching current are accordance with those for magnetization reversal by spin transfer torque originated from the spin Hall effect in the Ta layer.

  10. Evidence for Triplet Superconductivity in a Superconductor-Ferromagnet Spin Valve P. V. Leksin,1

    E-Print Network [OSTI]

    Fominov, Yakov

    Evidence for Triplet Superconductivity in a Superconductor-Ferromagnet Spin Valve P. V. Leksin,1 N on the mutual orientation of magnetizations of Fe1 and Fe2 layers in the spin valve system CoOx=Fe1=Cu=Fe2=Pb of the SC triplet spin valve theory gives direct evidence for the long-range triplet superconductivity

  11. PHYSICAL REVIEW B 91, 214508 (2015) Superconducting spin-valve effect and triplet superconductivity

    E-Print Network [OSTI]

    Fominov, Yakov

    2015-01-01

    PHYSICAL REVIEW B 91, 214508 (2015) Superconducting spin-valve effect and triplet superconductivity 12 June 2015) We report magnetic and superconducting properties of the modified spin-valve system Co theoretical description of the superconducting spin-valve effect and of the manifestation of the long

  12. 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

  13. 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

    2011-01-01

    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...

  14. Quantum Otto engine with a spin $1/2$ coupled to an arbitrary spin

    E-Print Network [OSTI]

    Ferdi Altintas; Özgür E. Müstecapl?o?lu

    2015-06-30

    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 spins 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.

  15. 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

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

    SciTech Connect (OSTI)

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

    2014-02-28

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

  17. High spin states in {sup 139}Pm

    SciTech Connect (OSTI)

    Dhal, A.; Sinha, R. K.; Chaturvedi, L.; Agarwal, P.; Kumar, S.; Jain, A. K.; Kumar, R.; Govil, I. M.; Mukhopadhyay, S.; Chakraborty, A.; Krishichayan; Ray, S.; Ghugre, S. S.; Sinha, A. K.; Kumar, R.; Singh, R. P.; Muralithar, S.; Bhowmik, R. K.; Pancholi, S. C.; Gupta, J. B. [Department of Physics, Banaras Hindu University, Varanasi-221 005 (India); Department of Physics, IIT Roorkee, Roorkee-247 667 (India); Department of Physics, Panjab University, Chandigarh-160 014 (India); UGC-DAE Consortium for Scientific Research, Kolkata Centre, Kolkata-700 098 (India); Inter University Accelerator Centre, New Delhi-110 067 (India); Ramjas College, Delhi University, Delhi-110 007 (India)

    2009-07-15

    The odd mass nucleus {sup 139}Pm has been studied to high spins through the {sup 116}Cd({sup 27}Al,4n){sup 139}Pm reaction at an incident beam energy of 120 MeV. The de-exciting {gamma}-rays were detected using an array of 12 Compton suppressed Ge detectors. A total of 46 new levels have been proposed in the present work as a result of the observation of 60 new {gamma}-rays. Four new bands including a {delta}J=1 sequence have been identified and all the earlier reported bands, other than the yrast band, have been extended to higher spins and excitation energy. The spin assignments for most of the newly reported levels have been made using the observed coincidence angular anisotropy. Tilted axis cranking calculations support the interpretation of two of the observed magnetic dipole sequences as examples of magnetic rotational bands.

  18. Complex behavior in simple spin systems

    E-Print Network [OSTI]

    Bush, S.D.

    2010-01-01

    evidence that our radiation damping detection scheme isthe NMR detection coil and sample (radiation damping) tonature of radiation damping to push the detection limitation

  19. 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)

    2014-06-21

    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.

  20. Viewing spin structures with soft x-ray microscopy

    SciTech Connect (OSTI)

    Fischer, Peter

    2010-06-01

    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.

  1. 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

  2. A Region of High-Spin Toroidal Isomers

    SciTech Connect (OSTI)

    Staszczak, A.; Wong, Cheuk-Yin

    2014-11-01

    The combined considerations of both the bulk liquid-drop-type behavior and the quantized angular momentum reveal that high-spin toroidal isomeric states may have general occurrences for light nuclei with 28 < A < 52. High-spin N=Z toroidal isomers in this mass region have been located theoretically using cranked self-consistent constraint Skyrme Hartree Fock model calculations.

  3. 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)

    2005-08-15

    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.

  4. Magnetic interactions in ?-Fe{sub 2}O{sub 3}@SiO{sub 2} nanocomposites

    SciTech Connect (OSTI)

    El Mendili, Y.; Bardeau, J.-F.; Greneche, J.-M.; Randrianantoandro, N.; Grasset, F.; Cador, O.; Guizouarn, T.

    2014-08-07

    Structural and magnetic properties of ?-Fe{sub 2}O{sub 3} nanoparticles of 4?nm diameter, dispersed into silica SiO{sub 2} matrix with a wide range value of volume fraction (0.05 to 1), were investigated. Produced ?-Fe{sub 2}O{sub 3}@SiO{sub 2} nanocomposites consist of an assembly of very small single domain magnetic object (<10?nm) with a random distribution of both inter-particle distance and direction of particle magnetic moment. We focused on the determination of a magnetic percolation threshold, defined as the magnetic particles concentration value above which the magnetic properties of isolated particles vanished in favor of a magnetic collective behavior induced by magnetic interactions. A percolation threshold value of 0.63 was obtained by a local probe technique such as {sup 57}Fe Mössbauer spectrometry and confirmed by global magnetic measurements through zero-field cooled, field-cooled, and ac susceptibility data. Below this threshold, dynamic ac magnetization measurements show a thermally activated Arrhenius dependence of the blocking temperature of superparamagnetic nanoparticles and above this critical value, one observes a slowing down of their dynamic properties, which lead toward the establishment of a spin-glass like state.

  5. 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)

    2010-09-03

    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.

  6. 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

    2009-01-01

    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.

  7. Magnetic Edge States in Graphene

    E-Print Network [OSTI]

    Gabriela Murguia

    2010-08-29

    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.

  8. Magnetic Edge States in Graphene

    E-Print Network [OSTI]

    Murguia, Gabriela

    2010-01-01

    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.

  9. Evidence for spin selectivity of triplet pairs in superconducting spin valves

    E-Print Network [OSTI]

    Banerjee, N.; Smiet, C. B.; Smits, R. G. J.; Ozaeta, A.; Bergeret, F. S.; Blamire, M. G.; Robinson, J. W. A.

    2014-01-09

    Evidence for spin-selectivity of triplet pairs in superconducting spin-valves N. Banerjee1, C. B. Smiet1, R. G. J. Smits1, A. Ozaeta2, F. S. Bergeret2, M. G. Blamire1, J. W. A. Robinson1* 1Department of Materials Science and Metallurgy, University... . Pang, B. S. H., Bell, C., Tomov, R. I., Durrell, J. H., & Blamire, M. G. Pseudo spin-valve behavior in oxide ferromagnet/superconductor/ferromagnet trilayers. Phys. Lett. A 341, 313–319 (2005). 35. Kalcheim, Y., Kirzhner, T., Koren, G. & Millo, O...

  10. Insensitivity of tunneling anisotropic magnetoresistance to non-magnetic electrodes

    SciTech Connect (OSTI)

    Wang, Y. Y.; Song, C. Wang, G. Y.; Zeng, F.; Pan, F.

    2013-11-11

    Ferromagnetic electrodes play a crucial role in magnetoresistance effect and spin injection, whereas the essential features of non-magnetic metal electrodes in spintronics are commonly ignored except for their electrical conductivity. Here, we verify that the room-temperature tunneling anisotropic magnetoresistance (TAMR) behavior in antiferromagnet-based [Pt/Co]/IrMn/AlO{sub x}/metal (metal?=?Pt, Au, Cu, Al) junctions is insensitive to the top metal electrodes. Similar out-of-plane signals are detected for different electrodes, in contrast to the varied shapes of in-plane TAMR curves which are most likely attributed to the differences in the multidomain structure of the magnetic electrode. This would add a different dimension to spintronics.

  11. 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)

    2014-01-27

    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.

  12. Ageing at the Spin-Glass/Ferromagnet Transition: Monte Carlo Simulation using Markus Manssen

    E-Print Network [OSTI]

    Peinke, Joachim

    exponents. We observe a clear signature of the disorder-driven equilibrium transition in the non by a rough free-energy landscape and by slow glassy dynamics.7,8 Disorder and frustration in the spin-spin interactions were identified as the under- lying principles governing the behavior of spin glasses. Thus

  13. SPIN-TORQUE IN SYSTEMS WITH INHOMOGENEOUS MAGETIZATION

    SciTech Connect (OSTI)

    Zangwill, Andrew

    2013-04-23

    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.

  14. 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

    2009-03-02

    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.

  15. Hyperfine-induced spin relaxation of a diffusively moving carrier in low dimensions: Implications for spin transport in organic semiconductors

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

    Mkhitaryan, V. V.; Dobrovitski, V. V.

    2015-08-24

    The hyperfine coupling between the spin of a charge carrier and the nuclear spin bath is a predominant channel for the carrier spin relaxation in many organic semiconductors. We theoretically investigate the hyperfine-induced spin relaxation of a carrier performing a random walk on a d-dimensional regular lattice, in a transport regime typical for organic semiconductors. We show that in d=1 and 2, the time dependence of the space-integrated spin polarization P(t) is dominated by a superexponential decay, crossing over to a stretched-exponential tail at long times. The faster decay is attributed to multiple self-intersections (returns) of the random-walk trajectories, whichmore »occur more often in lower dimensions. We also show, analytically and numerically, that the returns lead to sensitivity of P(t) to external electric and magnetic fields, and this sensitivity strongly depends on dimensionality of the system (d=1 versus d=3). We investigate in detail the coordinate dependence of the time-integrated spin polarization ?(r), which can be probed in the spin-transport experiments with spin-polarized electrodes. We also demonstrate that, while ?(r) is essentially exponential, the effect of multiple self-intersections can be identified in transport measurements from the strong dependence of the spin-decay length on the external magnetic and electric fields.« less

  16. Level Structure of 103Ag at high spins

    E-Print Network [OSTI]

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

    2007-01-01

    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

  17. 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

    2007-12-07

    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

  18. Quantum chaos and fluctuations in isolated nuclear-spin systems

    SciTech Connect (OSTI)

    Ludlow, J. A.; Sushkov, O. P. [School of Physics, University of New South Wales, Sydney 2052 (Australia)

    2007-01-15

    Using numerical simulations we investigate dynamical quantum chaos in isolated nuclear spin systems. We determine the structure of quantum states, investigate the validity of the Curie law for magnetic susceptibility and find the spectrum of magnetic noise. The spectrum is the same for positive and negative temperatures. The study is motivated by recent interest in condensed-matter experiments for searches of fundamental parity- and time-reversal-invariance violations. In these experiments nuclear spins are cooled down to microkelvin temperatures and are completely decoupled from their surroundings. A limitation on statistical sensitivity of the experiments arises from the magnetic noise.

  19. 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; Dai, Pengcheng; Fernandez-Baca, Jaime A; Adroja, D. T.; Perring, T. G.; Tomioka, Y.; Tokura, Y.

    2007-01-01

    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.

  20. 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; Dai, Pengcheng; Fernandez-Baca, Jaime A; Adroja, D. T.; Perring, T. G.; Tomioka, Y.; Tokura, Y.

    2007-01-01

    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.

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

    SciTech Connect (OSTI)

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

    2015-03-05

    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 be 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

  2. 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

    2015-03-05

    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

  3. The magnetic dipole interaction in Einstein-Maxwell theory

    E-Print Network [OSTI]

    W. B. Bonnor

    2002-03-13

    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.

  4. Detection of atomic spin labels in a lipid bi-layer using a single-spin nanodiamond probe

    E-Print Network [OSTI]

    Kaufmann, Stefan; Hall, Liam T; Perunicic, Viktor; Senn, Philipp; Steinert, Steffen; McGuinness, Liam P; Johnson, Brett C; Ohshima, Takeshi; Caruso, Frank; Wrachtrup, Joerg; Scholten, Robert E; Mulvaney, Paul; Hollenberg, Lloyd C L

    2013-01-01

    Magnetic field fluctuations arising from fundamental spins are ubiquitous in nanoscale biology, and are a rich source of information about the processes that generate them. However, the ability to detect the few spins involved without averaging over large ensembles has remained elusive. Here we demonstrate the detection of gadolinium spin labels in an artificial cell membrane under ambient conditions using a single-spin nanodiamond sensor. Changes in the spin relaxation time of the sensor located in the lipid bilayer were optically detected and found to be sensitive to near-individual proximal gadolinium atomic labels. The detection of such small numbers of spins in a model biological setting, with projected detection times of one second, opens a new pathway for in-situ nanoscale detection of dynamical processes in biology.

  5. Influence of Bridgman solidification on microstructures and magnetic behaviors of a non-equiatomic FeCoNiAlSi high-entropy alloy

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

    Zuo, Tingting; Yang, Xiao; Liaw, Peter K.; Zhang, Yong

    2015-09-07

    The non-equiatomic FeCoNiAlSi alloy is prepared by the Bridgman solidification (BS) technique at different withdrawal velocities (V = 30, 100, and 200 ?m/s). Various characterization techniques have been used to study the microstructure and crystal orientation. The morphological evolutions accompanying the crystal growth of the alloy prepared at different withdrawal velocities are nearly the same, from equiaxed grains to columnar crystals. The transition of coercivity is closely related to the local microstructure, while the saturation magnetization changes little at different sites. The coercivity can be significantly reduced from the equiaxed grain area to the columnar crystal area when the appliedmore »magnetic field direction is parallel to the crystal growth direction, no matter what is the withdrawal velocity. As a result, the alloy possesses magnetic anisotropy when the applied magnetic field is in different directions.« less

  6. 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.

    2012-04-27

    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

  7. 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)

    2014-05-07

    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.

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

    SciTech Connect (OSTI)

    Sendil Kumar, A. E-mail: anilb42@gmail.com; Manivel Raja, M.; Bhatnagar, Anil K. E-mail: anilb42@gmail.com

    2014-09-21

    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.

  9. Giant spin-accumulation signal and pure spin-current-induced reversible

    E-Print Network [OSTI]

    Loss, Daniel

    current is non-local electrical-spin injection12­18 , but this approach has suffered so far from low injection efficiency. Here, we demonstrate a significant enhancement of the non-local injection efficiency a charge current1­11 . This charge-current-induced magnetization switching (CIMS) is the result of a direct

  10. Nuclear magnetic Trond Saue (LCPQ, Toulouse) Nuclear magnetic resonance Virginia Tech 2015 1 / 51

    E-Print Network [OSTI]

    Crawford, T. Daniel

    Nuclear magnetic resonance Trond Saue Trond Saue (LCPQ, Toulouse) Nuclear magnetic resonance Virginia Tech 2015 1 / 51 #12;Nuclear spin The atomic nucleus is a composite particle built from Z protons (LCPQ, Toulouse) Nuclear magnetic resonance Virginia Tech 2015 1 / 51 #12;Gyromagnetic ratio: classical

  11. Spin-Nematic Squeezing in a Quantum Gas

    E-Print Network [OSTI]

    Hamley, C D; Hoang, T M; Bookjans, E M; Chapman, M S

    2011-01-01

    Exotic types of magnetic order and phases resulting from collective behaviour of quantum spins are an important focus of many-body physics. Nematic or quadrupolar ordering of spins is one such example, which breaks O(3) rotational symmetry, has no magnetic moment and is analogous to the well-known ordering of molecules in nematic phases of liquid crystals. Spin nematic phases have been posited for a variety of condensed matter systems including frustrated quantum magnets, and heavy-fermion and iron-based superconductors, although they are challenging to detect directly. Spin-1 atomic Bose-Einstein condensates provide a natural system to investigate spin-nematic quantum phases with a key advantage that the nematic tensor is directly measurable. Here, we measure spin-nematic fluctuations in a spin-1 condensate following a quench through a nematic to ferromagnetic quantum phase transition and observe quadrature squeezing in the variance of the fluctuations up to -8.3 dB (-10.3 dB corrected for detection noise) b...

  12. Spintronic transport of a non-magnetic molecule between magnetic electrodes

    SciTech Connect (OSTI)

    Kondo, Hisashi; Ohno, Takahisa; Institute of Industrial Science, University of Tokyo, Meguro, Tokyo 153-8505

    2013-12-02

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

  13. A study of Overhauser pumping in weak magnetic fields 

    E-Print Network [OSTI]

    Gondran, Gregory Rhea

    1986-01-01

    RESONANCE THEORY. . Basic Dynamics Larmor Precession; Effect of a Rotating Field III. SPIN ENSEMBLES Paramagnetism The Bloch Equation Relaxation Effects Steady State Solutions. IV. OVERHAUSER PUMPING . V. EXPERIMENTAL DETECTION METHOD . . The DC... for positive gyromagnetic ratio. III. SPIN ENSEMBLES Paramagnetism NMR deals with samples which have a net macroscopic magnetization due to the nuclear spins when placed in a static magnetic field B, . This effect is known as:nuclear paramagnetism...

  14. Magnetization dynamics of cobalt grown on graphene

    SciTech Connect (OSTI)

    Berger, A. J.; White, S. P.; Adur, R.; Pu, Y.; Hammel, P. C.; Amamou, W.; Kawakami, R. K.

    2014-05-07

    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.

  15. Magnetoelectric effects and valley-controlled spin quantum gates in transition metal dichalcogenide bilayers

    SciTech Connect (OSTI)

    Gong, Zhirui; Liu, G. B.; Yu, Hongyi; Xiao, Di; Cui, Xiaodong; Xu, Xiaodong; Yao, Wang

    2013-01-01

    In monolayer group-VI transition metal dichalcogenides, charge carriers have spin and valley degrees of freedom, both associated with magnetic moments. On the other hand, the layer degree of freedom in multilayers is associated with electrical polarization. Here we show that transition metal dichalcogenide bilayers offer an unprecedented platform to realize a strong coupling between the spin, valley and layer pseudospin of holes. Such coupling gives rise to the spin Hall effect and spin-dependent selection rule for optical transitions in inversion symmetric bilayer and leads to a variety of magnetoelectric effects permitting quantum manipulation of these electronic degrees of freedom. Oscillating electric and magnetic fields can both drive the hole spin resonance where the two fields have valley-dependent interference, making an interplay between the spin and valley as information carriers possible for potential valley-spintronic applications. We show how to realize quantum gates on the spin qubit controlled by the valley bit.

  16. Spin-state responses to light impurity doping in low-spin perovskite LaCoO$_{3}$

    E-Print Network [OSTI]

    Tomiyasu, Keisuke; Shimomura, Saya; Onodera, Mitsugi; Nakao, Hironori; Murakami, Youichi

    2012-01-01

    We studied the spin-state responses to light impurity doping in low-spin perovskite LaCoO$_{3}$ (Co^3+: d^6) through magnetization and X-ray fluorescence measurements of single-crystal LaCo$_{0.99}$$M_{0.01}$O$_{3}$ ($M$ = Cr, Mn, Fe, Ni). In the magnetization curves measured at 1.8 K, a change in the spin-state was not observed for Cr, Mn, or Fe doping but was observed for Ni doping. Strong magnetic anisotropy along the [100] easy axis was also found in the Ni-doped sample. The fluorescence measurements revealed that the valences were roughly estimated to be Cr^3+, Mn^4+, Fe^(3+delta)+, and Ni^3+. From the observed chemical trends, we propose that the chemical potential is a key factor in inducing the change of the low-spin state. By expanding a model of the ferromagnetic spin-state heptamer generated by hole doping, we discuss the emergence of highly anisotropic ferromagnetic spin-state clusters induced by low-spin Ni^3+ with Jahn-Teller activity. We also discuss applicability of the present results to mant...

  17. 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)

    2013-12-02

    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.

  18. Optimized fabrication and characterization of carbon nanotube spin valves

    SciTech Connect (OSTI)

    Samm, J.; Gramich, J.; Baumgartner, A. Weiss, M.; Schönenberger, C.

    2014-05-07

    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.

  19. Spin-Lattice Coupling and Superconductivity in Fe Pnictides

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

    Egami, T.; Fine, B. V.; Parshall, D.; Subedi, A.; Singh, D. J.

    2010-01-01

    We consider strong spin-lattice and spin-phonon coupling in iron pnictides and discuss its implications on superconductivity. Strong magneto-volume effect in iron compounds has long been known as the Invar effect. Fe pnictides also exhibit this effect, reflected in particular on the dependence of the magnetic moment on the atomic volume of Fe defined by the positions of the nearest neighbor atoms. Through the phenomenological Landau theory, developed on the basis of the calculations by the density functional theory (DFT) and the experimental results, we quantify the strength of the spin-lattice interaction as it relates to the Stoner criterion for themore »onset of magnetism. We suggest that the coupling between electrons and phonons through the spin channel may be sufficiently strong to be an important part of the superconductivity mechanism in Fe pnictides.« less

  20. 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.

    2010-03-19

    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.

  1. Spin-dependent delay time in ferromagnet/insulator/ferromagnet heterostructures

    SciTech Connect (OSTI)

    Xie, ZhengWei; Zheng Shi, De; Lv, HouXiang

    2014-07-07

    We study theoretically spin-dependent group delay and dwell time in ferromagnet/insulator/ferromagnet (FM/I/FM) heterostructure. The results indicate that, when the electrons with different spin orientations tunnel through the FM/I/FM junction, the spin-up process and the spin-down process are separated on the time scales. As the self-interference delay has the spin-dependent features, the variations of spin-dependent dwell-time and spin-dependent group-delay time with the structure parameters appear different features, especially, in low incident energy range. These different features show up as that the group delay times for the spin-up electrons are always longer than those for spin-down electrons when the barrier height or incident energy increase. In contrast, the dwell times for the spin-up electrons are longer (shorter) than those for spin-down electrons when the barrier heights (the incident energy) are under a certain value. When the barrier heights (the incident energy) exceed a certain value, the dwell times for the spin-up electrons turn out to be shorter (longer) than those for spin-down electrons. In addition, the group delay time and the dwell time for spin-up and down electrons also relies on the comparative direction of magnetization in two FM layers and tends to saturation with the thickness of the barrier.

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

    SciTech Connect (OSTI)

    Das, Tanmoy [Los Alamos National Laboratory

    2012-06-05

    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.

  3. Resonant and non-resonant magnetic scattering

    SciTech Connect (OSTI)

    McWhan, D.B.; Hastings, J.B.; Kao, C.C.; Siddons, D.P.

    1991-12-31

    The tunability and the polarization of synchrotron radiation open upon new possibilities for the study of magnetism. Studies on magnetic materials performed at the National Synchrotron Light Source are reviewed, and thy fall into four areas: structure, evolution of magnetic order, separation of L and S, and resonance effects. In the vicinity of atomic absorption edges, the Faraday effect, magnetic circular dichroism, and resonant magnetic scattering are all related resonance effects which measure the spin polarized density of states. The production and analysis of polarized beams are discussed in the context of the study of magnetism with synchrotron radiation.

  4. Resonant and non-resonant magnetic scattering

    SciTech Connect (OSTI)

    McWhan, D.B.; Hastings, J.B.; Kao, C.C.; Siddons, D.P.

    1991-01-01

    The tunability and the polarization of synchrotron radiation open upon new possibilities for the study of magnetism. Studies on magnetic materials performed at the National Synchrotron Light Source are reviewed, and thy fall into four areas: structure, evolution of magnetic order, separation of L and S, and resonance effects. In the vicinity of atomic absorption edges, the Faraday effect, magnetic circular dichroism, and resonant magnetic scattering are all related resonance effects which measure the spin polarized density of states. The production and analysis of polarized beams are discussed in the context of the study of magnetism with synchrotron radiation.

  5. 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

    2006-12-29

    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, $M_z$.

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

    SciTech Connect (OSTI)

    Taniguchi, Tomohiro; Tsunegi, Sumito; Kubota, Hitoshi; Imamura, Hiroshi

    2014-04-14

    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.

  7. Effects of Ga substitution on the structural and magnetic properties of half metallic Fe{sub 2}MnSi Heusler compound

    SciTech Connect (OSTI)

    Pedro, S. S. Caraballo Vivas, R. J.; Andrade, V. M.; Cruz, C.; Paixão, L. S.; Contreras, C.; Costa-Soares, T.; Rocco, D. L.; Reis, M. S.; Caldeira, L.; Coelho, A. A.; Carvalho, A. Magnus G.

    2015-01-07

    The so-called half-metallic magnets have been proposed as good candidates for spintronic applications due to the feature of exhibiting a hundred percent spin polarization at the Fermi level. Such materials follow the Slater-Pauling rule, which relates the magnetic moment with the valence electrons in the system. In this paper, we study the bulk polycrystalline half-metallic Fe{sub 2}MnSi Heusler compound replacing Si by Ga to determine how the Ga addition changes the magnetic, the structural, and the half-metal properties of this compound. The material does not follow the Slater-Pauling rule, probably due to a minor structural disorder degree in the system, but a linear dependence on the magnetic transition temperature with the valence electron number points to the half-metallic behavior of this compound.

  8. Fast, low-power manipulation of spin ensembles in superconducting microresonators

    SciTech Connect (OSTI)

    Sigillito, A. J., E-mail: asigilli@princeton.edu; Malissa, H.; Tyryshkin, A. M.; Houck, A. A.; Lyon, S. A. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Riemann, H.; Abrosimov, N. V. [Institut für Kristallzüchtung, D-12489 Berlin (Germany); Becker, P. [Physikalisch-Technische Bundesanstalt, D-38116 Braunschweig (Germany); Pohl, H.-J. [VITCON Projectconsult GMBH, D-07745 Jena (Germany); Thewalt, M. L. W. [Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); Itoh, K. M. [School of Fundamental Science and Technology, Keio University, Yokohama, Kanagawa 2238522 (Japan); Morton, J. J. L. [London Centre for Nanotechnology, University College London, London WC1H 0AH (United Kingdom); Schuster, D. I. [Department of Physics and James Franck Institute, University of Chicago, Chicago, Illinois 60637 (United States)

    2014-06-02

    We demonstrate the use of high-Q superconducting coplanar waveguide (CPW) microresonators to perform rapid manipulations on a randomly distributed spin ensemble using very low microwave power (400 nW). This power is compatible with dilution refrigerators, making microwave manipulation of spin ensembles feasible for quantum computing applications. We also describe the use of adiabatic microwave pulses to overcome microwave magnetic field (B{sub 1}) inhomogeneities inherent to CPW resonators. This allows for uniform control over a randomly distributed spin ensemble. Sensitivity data are reported showing a single shot (no signal averaging) sensitivity to 10{sup 7} spins or 3×10{sup 4}spins/?(Hz) with averaging.

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

    SciTech Connect (OSTI)

    Fukuda, Masahiro; Senami, Masato; Ogiso, Yoji; Tachibana, Akitomo

    2014-10-06

    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.

  10. Electronic behavior of highly correlated metals

    SciTech Connect (OSTI)

    Reich, A.

    1988-10-01

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

  11. One and two spin$-1/2$ particles systems under Lorentz transformations

    E-Print Network [OSTI]

    H. Moradpour; M. Bahadoran

    2015-06-29

    We consider two inertia frames, including the lab and moving frames, connected to each other by a Lorentz transformation. Thereinafter, we point to a one spin$-1/2$ particle system and study the effects of Lorentz transformation on its state. Moreover, we address the predictions made by Czachor's and the Pauli spin operators about the spin behavior and compare results with the behavior of system state under Lorentz transformation. This investigation shows that the predictions made by considering the Pauli spin operator about the spin of system are in better agreement with the system state compared with those of made by considering Czachor's spin operator. In continue, we focus on two-particle pure entangled systems including two spin$-1/2$ particles which moves away from each other. Once again, we investigate the behavior of system state under Lorentz transformation. We also point to the behavior of Bell's inequality, as a witness for non-locality, under Lorentz transformation. Our study shows that the Bell operator made by the Pauli operator has better consistency with the behavior of spin state of system under Lorentz transformation compared with the Bell operator made by Czachor's operator. Our approach may also be used to study the relation between the various spin operators and the effects of Lorentz transformation on system, helping us get some predictions about the outcome of a Stern-Gerlach type experiment in relativistic situations.

  12. Spin coating apparatus

    DOE Patents [OSTI]

    Torczynski, John R. (Albuquerque, NM)

    2000-01-01

    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.

  13. Controlled Spin Transport in Planar Systems Through Topological Exciton

    E-Print Network [OSTI]

    Kumar Abhinav; Prasanta K. Panigrahi

    2015-07-01

    It is shown that a charge-neutral spin-1 exciton, realizable only in planar systems like graphene, can effectively be used for controlled spin transport in such media. The excitonic bound state is destabilized by quantum fluctuations, characterized by a threshold for excitation and melts in a smooth manner under thermal fluctuations. This planar exciton differs from the conventional ones, as it owes its existence to the topological Chern-Simons (CS) term. The parity and time-reversal violating CS term can arise from quantum effects in systems with parity-breaking mass-gap. The spinning exciton naturally couples to magnetic field, leading to the possibility of controlled spin transport. Being neutral, it is immune to adverse effects, afflicting spin transport by charged fermions.

  14. 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)

    2006-07-15

    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.

  15. Spacetime dynamics of spinning particles - exact gravito-electromagnetic analogies

    E-Print Network [OSTI]

    L. Filipe O. Costa; José Natário; Miguel Zilhão

    2015-07-29

    We compare the rigorous equations describing the motion of spinning test particles in gravitational and electromagnetic fields, and show that if the Mathisson-Pirani spin condition holds then exact gravito-electromagnetic analogies emerge. These analogies provide a familiar formalism to treat gravitational problems, as well as a means for comparing the two interactions. Fundamental differences are manifest in the symmetries and time projections of the electromagnetic and gravitational tidal tensors. The physical consequences of the symmetries of the tidal tensors are explored comparing the following analogous setups: magnetic dipoles in the field of non-spinning/spinning charges, and gyroscopes in the Schwarzschild, Kerr, and Kerr-de Sitter spacetimes. The implications of the time-projections of the tidal tensors are illustrated by the work done on the particle in various frames; in particular, a reciprocity is found to exist: in a frame comoving with the particle, the electromagnetic (but not the gravitational) field does work on it, causing a variation of its proper mass; conversely, for "static observers", a stationary gravitomagnetic (but not a magnetic) field does work on the particle, and the associated potential energy is seen to embody the Hawking-Wald spin-spin interaction energy. The issue of hidden momentum, and its counterintuitive dynamical implications, is also analyzed. Finally, a number of issues regarding the electromagnetic interaction are clarified, namely the differences in the dynamics of electric and magnetic dipoles, and the physical meaning of Dixon's equations.

  16. Stationary and transient leakage current in the Pauli spin blockade

    E-Print Network [OSTI]

    F. Qassemi; W. A. Coish; F. K. Wilhelm

    2009-04-22

    We study the effects of cotunneling and a non-uniform Zeeman splitting on the stationary and transient leakage current through a double quantum dot in the Pauli spin blockade regime. We find that the stationary current due to cotunneling vanishes at low temperature and large applied magnetic field, allowing for the dynamical preparation of a pure spin ground state, even at large voltage bias. Additionally, we analyze current that flows between blocking events, characterized, in general, by a fractional effective charge $e^*$. This charge can be used as a sensitive probe of spin relaxation mechanisms and can be used to determine the visibility of Rabi oscillations.

  17. Nanoconstriction-based spin-Hall nano-oscillator

    SciTech Connect (OSTI)

    Demidov, V. E.; Urazhdin, S.; Zholud, A.; Sadovnikov, A. V.; Demokritov, S. O.

    2014-10-27

    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. Nuclear spin qubits in a trapped-ion quantum computer

    E-Print Network [OSTI]

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

    2009-04-26

    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.

  19. Optical hyperpolarization of 13C nuclear spins in nanodiamond ensembles

    E-Print Network [OSTI]

    Q. Chen; I. Schwarz; F. Jelezko; A. Retzker; M. B. Plenio

    2015-04-09

    Here we propose and analyse in detail protocols that can achieve rapid hyperpolarization of 13C nuclear spins in randomly oriented ensembles of nanodiamonds at room temperature. Our protocols exploit a combination of optical polarization of electron spins in nitrogen-vacancy centers and the transfer of this polarization to 13C nuclei by means of microwave control to overcome the severe challenges that are posed by the random orientation of the nanodiamonds and their nitrogen-vacancy centers. Specifically, these random orientations result in exceedingly large energy variations of the electron spin levels that render the polarization and coherent control of the nitrogen-vacancy center electron spins as well as the control of their coherent interaction with the surrounding 13C nuclear spins highly inefficient. We address these challenges by a combination of an off-resonant microwave double resonance scheme in conjunction with a realization of the integrated solid effect which, together with adiabatic rotations of external magnetic fields or rotations of nanodiamonds, leads to a protocol that achieves high levels of hyperpolarization of the entire nuclear-spin bath in a randomly oriented ensemble of nanodiamonds even at room temperature. This hyperpolarization together with the long nuclear spin polarization lifetimes in nanodiamonds and the relatively high density of 13C nuclei has the potential to result in a major signal enhancement in 13C nuclear magnetic resonance imaging and suggests functionalized and hyperpolarized nanodiamonds as a unique probe for molecular imaging both in vitro and in vivo.

  20. Magnetic Interactions in Ball-Milled Spinel Ferrites

    E-Print Network [OSTI]

    Goya, Gerardo F

    2011-01-01

    Spinel Fe3O4 nanoparticles have been produced through ball milling in methyl-alcohol (CH3OH), aiming to obtain samples with similar average particle sizes and different interparticle interactions. Three samples having Fe3O4/CH3(OH) mass ratios R of 3 %, 10 % and 50 % wt. were milled for several hours until particle size reached a steady value ( ~ 7-10 nm). A detailed study of static and dynamic magnetic properties has been undertaken by measuring magnetization, ac susceptibility and M\\"ossbauer data. As expected for small particles, the Verwey transition was not observed, but instead superparamagnetic (SPM) behavior was found with transition to a blocked state at TB ~ 10-20 K. Spin disorder of the resulting particles, independent of its concentration, was inferred from the decrease of saturation magnetization MS at low temperatures. For samples having 3% wt. of magnetic particles, dynamic ac susceptibility measurements show a thermally activated Arrhenius dependence of the blocking temperature with applied f...

  1. 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

    2014-11-07

    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.

  2. 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.

    2012-04-01

    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.

  3. Electric Dipole Moment of Magnetic Monopole

    E-Print Network [OSTI]

    Makoto Kobayashi

    2007-03-07

    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).

  4. Spin Transport Shingo Katsumoto

    E-Print Network [OSTI]

    Iye, Yasuhiro

    -1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan According to DARPA's definition, "Spintronics"[1] means "Spin Transport Electronics". The issue "Spin Trans- port" thus covers all the fields of spintronics and one devices. In semiconductor spintronics devices, we therefore utilize the differences in n, , m for up

  5. Spin Coating of Photoresists

    E-Print Network [OSTI]

    Yoo, S. J. Ben

    Spin Coating of Photoresists Revised: 2009-11-05 Source: www.microchemicals.eu e-Mail: sales@microchemicals.eu Basics of Spin Coating During spincoating, the centrifugal force the substrate. Advantages: The high resist film thickness homogeneity as well as the short coating times make

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

    SciTech Connect (OSTI)

    Pappas, S. D.; Trachylis, D.; Velgakis, M. J.; Kapaklis, V.; Joensson, P. E.; Papaioannou, E. Th.; Delimitis, A.; Poulopoulos, P.; Fumagalli, P.; Politis, C.

    2012-09-01

    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.

  7. Current-induced torque driven ferromagnetic resonance in magnetic microstructures

    E-Print Network [OSTI]

    Fang, Dong

    2011-03-15

    of this Thesis a b Figure 1.2: An illustration of the spin-transfer torque effect in spin-valve device structures, adapted from [36]. a, A single magnetic layer with a spin- polarised electron passing through it. The magnet transmits and scatters the collinear... when an electric current passes through the pinned layer of a spin-valve, which can then act on the magnetisation in the free layer. 5 1.2 Context of this Thesis The current-induced torque in uniform ferromagnets has its origin in two quantum mechanical...

  8. Transverse Spin Physics: Recent Developments

    E-Print Network [OSTI]

    Yuan, Feng

    2009-01-01

    that the transverse spin physics is playing a very importantrole in the strong interaction physics forhadronic spin physics. We will learn more about QCD dynamics

  9. Controlling the magnetic susceptibility in an artificial elliptical quantum ring by magnetic flux and external Rashba effect

    SciTech Connect (OSTI)

    Omidi, Mahboubeh Faizabadi, Edris

    2015-03-21

    Magnetic susceptibility is investigated in a man-made elliptical quantum ring in the presence of Rashba spin-orbit interactions and the magnetic flux. It is shown that magnetic susceptibility as a function of magnetic flux changes between negative and positive signs periodically. The periodicity of the Aharonov-Bohm oscillations depends on the geometry of the region where magnetic field is applied, the eccentricity, and number of sites in each chain ring (the elliptical ring is composed of chain rings). The magnetic susceptibility sign can be reversed by tuning the Rashba spin-orbit strength as well. Both the magnetic susceptibility strength and sign can be controlled via external spin-orbit interactions, which can be exploited in spintronics and nanoelectronics.

  10. Depth Profile of Uncompensated Spins in an Exchange-Bias System

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

    and writing are finding that location makes just as much difference as it does in real estate. Consider the quantum mechanical spins that make some atoms magnetic. In a...

  11. 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

  12. Magnetic Properties and Reactivity Studies of Families of Trigonal Bipyramidal Cyanide Clusters and Their Extended Structures 

    E-Print Network [OSTI]

    Funck, Kristen Elise

    2012-02-14

    -optical devices, spintronics, and quantum computing. For any magnetic material, classical or molecular, to be useful, it is important to understand how the spin centers behave under a variety of conditions, particularly that there is an overall magnetic...

  13. Multiferroic heterostructures for spin filter application - an ab initio study

    E-Print Network [OSTI]

    Borek, Stephan; Ebert, Hubert; Minár, Ján

    2015-01-01

    Novel imaging spin-filter techniques, which are based on low energy electron diffraction, are currently of high scientific interest. To improve the spin-detection efficiency a variety of new materials have been introduced in recent years. A new class of promising spin-filter materials are represented by multiferroic systems, as both magnetic and electric ordering exist in these materials. We have investigated Fe/BaTiO3(001), which defines a prominent candidate due to its moderate spontaneous polarization, for spin filter applications calculating diffraction patterns for spin polarized electrons incident on the Fe surface. Motivated by the fact that spin polarized low energy electron diffraction is a powerful method for the determination of the properties of surfaces we investigated the influence of switching the BaTiO3 polarization on the exchange and spin orbit scattering as well as on reflectivity and figure of merit. This system obviously offers the possibility to realize a multiferroic spin filter and man...

  14. 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)

    2014-04-28

    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.

  15. Enhancement of Spin-transfer torque switching via resonant tunneling

    SciTech Connect (OSTI)

    Chatterji, Niladri; Tulapurkar, Ashwin A.; Muralidharan, Bhaskaran

    2014-12-08

    We propose the use of resonant tunneling as a route to enhance the spin-transfer torque switching characteristics of magnetic tunnel junctions. The proposed device structure is a resonant tunneling magnetic tunnel junction based on a MgO-semiconductor heterostructure sandwiched between a fixed magnet and a free magnet. Using the non-equilibrium Green's function formalism coupled self consistently with the Landau-Lifshitz-Gilbert-Slonczewski equation, we demonstrate enhanced tunnel magneto-resistance characteristics as well as lower switching voltages in comparison with traditional trilayer devices. Two device designs based on MgO based heterostructures are presented, where the physics of resonant tunneling leads to an enhanced spin transfer torque thereby reducing the critical switching voltage by up to 44%. It is envisioned that the proof-of-concept presented here may lead to practical device designs via rigorous materials and interface studies.

  16. 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

  17. A MEAN-FIELD MODEL FOR SPIN DYNAMICS IN MULTILAYERED FERROMAGNETIC MEDIA

    E-Print Network [OSTI]

    . Introduction. Spintronics, i.e., the active control and manipulation of spin degrees of freedom, plays a key-wall motion ([32]), a mechanism that is important in operating spintronic memories and logic devices ([15 as a result of this spin- transfer torque (see Figure 4.1). The magnetization reversal process in a spintronic

  18. Multivariate and univariate analysis of continuous arterial spin labeling perfusion MRI in Alzheimer's

    E-Print Network [OSTI]

    Multivariate and univariate analysis of continuous arterial spin labeling perfusion MRI arterial spin labeling (CASL) magnetic resonance imaging (MRI) was combined with multivariate analysis and precuneus. When tested on extensive split-half analysis to map out the replicability of both multivariate

  19. cond-mat/99020674Feb1999 Spin dynamics in high-TC

    E-Print Network [OSTI]

    Aksay, Ilhan A.

    in the SC state, is accompanied by a broader contribution located around 30 meV which remains above TC the full energy and momentum dependences of the spin-spin correlation function. Re- cently, efforts have exp-it (1) Our results are then directly comparable with both Nuclear Magnetic Res

  20. PHYSICAL REVIEW A 87, 013413 (2013) Spin damping in an rf atomic magnetometer

    E-Print Network [OSTI]

    Romalis, Mike

    2013-01-01

    the magnetometer for detection of the desired signal. We find that noise is also suppressed under such spin damping of spin damping during phase-sensitive detection suppresses both signal and noise in such a way excitation is used to create the signal, as in detection by nuclear magnetic or nuclear quadrupole resonance

  1. 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

  2. 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)

    2014-11-03

    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.

  3. 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

    2011-10-24

    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.

  4. Hysteretic Optimization For Spin Glasses

    E-Print Network [OSTI]

    B. Goncalves; S. Boettcher

    2007-12-10

    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.

  5. Surface magnetism of Gd(0001): Evidence of ferromagnetic coupling to bulk

    SciTech Connect (OSTI)

    Mulhollan, G.A.; Garrison, K.; Erskine, J.L. )

    1992-11-30

    Previous polarized electron experiments and recent {ital ab} {ital initio} calculations suggest that the surface layer magnetic moments of Gd(0001) are antiferromagnetically coupled to the bulk magnetic moments. Spin-polarized photoemission data are presented which show that the spin polarization of the magnetic surface state and the surface 4{ital f} states of Gd(0001) are coupled ferromagnetically to the bulk magnetic moment.

  6. Generation of spin-polarized currents via cross-relaxation with dynamically pumped paramagnetic impurities

    SciTech Connect (OSTI)

    Meriles, Carlos A.; Doherty, Marcus W.

    2014-07-14

    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.

  7. Shot noise of charge current in a quantum dot responded by rotating and oscillating magnetic fields

    SciTech Connect (OSTI)

    Zhao, Hong-Kang Zou, Wei-Ke; Chen, Qiao

    2014-09-07

    We have investigated the shot noise and Fano factor of the dynamic spin-polarized quantum dot under the perturbations of a rotating magnetic field (RMF), and an oscillating magnetic field (OMF) by employing the non-equilibrium Green's function approach. The shot noise is enhanced from sub-Poissonian to super-Poissonian due to the application of RMF and OMF, and it is controlled sensitively by the tilt angle ? of RMF. The magnitude of shot noise increases as the photon energy ?? of OMF increases, and its valley eventually is reversed to peaks as the photon energy is large enough. Double-peak structure of Fano factor is exhibited as the frequency of OMF increases to cover a large regime. The Zeeman energy ?{sub 0}B{sub 0} acts as an effective gate bias to exhibit resonant behavior, and novel peak emerges associated with the applied OMF.

  8. Magnetism and superconductivity in U2PtxRh1?xC2

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

    Wakeham, N.; Ni, Ni; Bauer, E. D.; Thompson, J. D.; Tegtmeier, E.; Ronning, F.

    2015-01-09

    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. Additionally, 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. Themore »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

  9. 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.

    2015-01-01

    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

  10. Electrical detection of 31P spin quantum states

    E-Print Network [OSTI]

    A. R. Stegner; C. Boehme; H. Huebl; M. Stutzmann; K. Lips; M. S. Brandt

    2006-07-25

    In recent years, a variety of solid-state qubits has been realized, including quantum dots, superconducting tunnel junctions and point defects. Due to its potential compatibility with existing microelectronics, the proposal by Kane based on phosphorus donors in Si has also been pursued intensively. A key issue of this concept is the readout of the P quantum state. While electrical measurements of magnetic resonance have been performed on single spins, the statistical nature of these experiments based on random telegraph noise measurements has impeded the readout of single spin states. In this letter, we demonstrate the measurement of the spin state of P donor electrons in silicon and the observation of Rabi flops by purely electric means, accomplished by coherent manipulation of spin-dependent charge carrier recombination between the P donor and paramagnetic localized states at the Si/SiO2 interface via pulsed electrically detected magnetic resonance. The electron spin information is shown to be coupled through the hyperfine interaction with the P nucleus, which demonstrates the feasibility of a recombination-based readout of nuclear spins.

  11. Spin splittings among charmed hadrons

    E-Print Network [OSTI]

    Randy Lewis; Nilmani Mathur; R. M. Woloshyn

    2001-09-19

    The mass differences between spin-1/2 and spin-3/2 baryons are compared to the mass differences between spin-0 and spin-1 mesons. Results of simulations for charmed hadrons in the quenched approximation from a tadpole-improved anisotropic action are discussed in the context of other lattice calculations, quark model predictions, heavy quark symmetry predictions and experimental data.

  12. Proposal for a graphene-based all-spin logic gate

    SciTech Connect (OSTI)

    Su, Li; Zhao, Weisheng; Zhang, Yue; Querlioz, Damien; Klein, Jacques-Olivier; Dollfus, Philippe; Bournel, Arnaud; Zhang, Youguang

    2015-02-16

    In this work, we present a graphene-based all-spin logic gate (G-ASLG) that integrates the functionalities of perpendicular anisotropy magnetic tunnel junctions (p-MTJs) with spin transport in graphene-channel. It provides an ideal integration of logic and memory. The input and output states are defined as the relative magnetization between free layer and fixed layer of p-MTJs. They can be probed by the tunnel magnetoresistance and controlled by spin transfer torque effect. Using lateral non-local spin valve, the spin information is transmitted by the spin-current interaction through graphene channels. By using a physics-based spin current compact model, the operation of G-ASLG is demonstrated and its performance is analyzed. It allows us to evaluate the influence of parameters, such as spin injection efficiency, spin diffusion length, contact area, the device length, and their interdependence, and to optimize the energy and dynamic performance. Compared to other beyond-CMOS solutions, longer spin information transport length (??m), higher data throughput, faster computing speed (?ns), and lower power consumption (??A) can be expected from the G-ASLG.

  13. arXiv:cond-mat/0305401v325Nov2003 Pyrochlore Photons: The U(1) Spin Liquid in a S = 1/2 Three-Dimensional Frustrated

    E-Print Network [OSTI]

    the properties of the soluble point we show that these models enter the U(1) spin liquid phase, a novel description of the U(1) spin liquid and the adjacent soluble point in terms of Gaussian quantum The search for quantum spin liquid states in frus- trated magnets can be traced back at least as far

  14. Temperature dependence of magnetization and anisotropy in uniaxial NiFe?O? 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)

    2014-10-21

    The thermal variation of magnetic anisotropy (K) and saturation magnetization (M{sub S}) for uniaxial nickel ferrite (NiFe?O?) 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}?.? in the whole temperature range violating the existing theoretical model by Callen and Callen. The unusual power-law behavior for the NiFe?O? 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.

  15. Fast deterministic switching in orthogonal spin torque devices via the control of the relative spin polarizations

    SciTech Connect (OSTI)

    Park, Junbo; Buhrman, R. A.; Ralph, D. C.; Kavli Institute at Cornell, Ithaca, New York 14853

    2013-12-16

    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.

  16. Spin states of para-water and ortho-water molecule in gas and liquid phases

    E-Print Network [OSTI]

    V. K. Konyukhov

    2009-09-23

    Spin degrees of freedom of water molecule in gas and liquid state were investigated in order to provide a reasonable answer about the unsolved problem of a long-term behavior of water spin isomers. The approach used involves an assumption that molecules change their spin state from a pure state to a mixed one when they interact with some sorts of adsorbent surface. Some models and conceptions of the quantum information processing were used.

  17. Quantum Model Of Spin Noise

    E-Print Network [OSTI]

    R. Annabestani; D. G. Cory; J. Emerson

    2015-03-03

    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.

  18. Magnetic edge states in Aharonov-Bohm graphene quantum rings

    SciTech Connect (OSTI)

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

    2013-12-07

    The effect of electron-electron interaction on the electronic structure of Aharonov-Bohm (AB) graphene quantum rings (GQRs) is explored theoretically using the single-band tight-binding Hamiltonian and the mean-field Hubbard model. The electronic states and magnetic properties of hexagonal, triangular, and circular GQRs with different sizes and zigzag edge terminations are studied. The results show that, although the AB oscillations in the all types of nanoring are affected by the interaction, the spin splitting in the AB oscillations strongly depends on the geometry and the size of graphene nanorings. We found that the total spin of hexagonal and circular rings is zero and therefore, no spin splitting can be observed in the AB oscillations. However, the non-zero magnetization of the triangular rings breaks the degeneracy between spin-up and spin-down electrons, which produces spin-polarized AB oscillations.

  19. Rapid characterizing of ferromagnetic materials using spin rectification

    SciTech Connect (OSTI)

    Fan, Xiaolong Wang, Wei; Wang, Yutian; Zhou, Hengan; Rao, Jinwei; Zhao, Xiaobing; Gao, Cunxu; Xue, Desheng; Gui, Y. S.; Hu, C.-M.

    2014-12-29

    Spin rectification is a powerful tool for dc electric detections of spin dynamics and electromagnetic waves. Technically, elaborately designed on-chip microwave devices are needed in order to realize that effect. In this letter, we propose a rapid characterizing approach based on spin rectification. By directly sending dynamic current into ferromagnetic films with stripe shape, resonant dc voltages can be detected along the longitudinal or transversal directions. As an example, Fe (010) films with precise crystalline structure and magnetic parameters were used to testify the reliability of such method. We investigated not only the dynamic parameters and the precise anisotropy constants of the Fe crystals but also the principle of spin rectification in this method.

  20. Heat-driven spin transport in a ferromagnetic metal

    SciTech Connect (OSTI)

    Xu, Yadong; Yang, Bowen; Tang, Chi; Jiang, Zilong; Shi, Jing; Schneider, Michael; Whig, Renu

    2014-12-15

    As a non-magnetic heavy metal is attached to a ferromagnet, a vertically flowing heat-driven spin current is converted to a transverse electric voltage, which is known as the longitudinal spin Seebeck effect (SSE). If the ferromagnet is a metal, this voltage is also accompanied by voltages from two other sources, i.e., the anomalous Nernst effect in both the ferromagnet and the proximity-induced ferromagnetic boundary layer. By properly identifying and carefully separating those different effects, we find that in this pure spin current circuit the additional spin current drawn by the heavy metal generates another significant voltage by the ferromagnetic metal itself which should be present in all relevant experiments.