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1.
Current-driven domain-wall motion is studied in (Ga,Mn)(As,P) ferromagnetic semiconducting tracks with perpendicular anisotropy. A linear steady state flow regime is observed over a large temperature range of the ferromagnetic phase (0.1T(c)相似文献
2.
《Physica E: Low-dimensional Systems and Nanostructures》2011,43(10):2673-2675
We report here on in-plane anisotropy observed in the tunneling magnetoresistance of (Ga,Mn)As/n+-GaAs Esaki diode contacts and in the spin polarization generated in lateral all-semiconductor, all-electrical spin injection devices, employing such Esaki-diode structures as spin aligning contacts. The uniaxial component of the registered anisotropies, observed along [1 1 0] directions, does switch its sign as an effect of the applied bias, however the switching occurs at different bias values for magnetoresistance and for spin polarization cases. 相似文献
3.
P. Sankowski P. Kacman J. Majewski T. Dietl 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):375
The Landauer–Büttiker formalism combined with the tight-binding transfer matrix method is used to describe the results of recent experiments: the high tunneling magnetoresistance (TMR) in (Ga,Mn)As-based trilayers and highly polarized spin injection in p-(Ga,Mn)As/n-GaAs Zener diode. For both TMR and Zener spin current polarization, the calculated values agree well with those observed experimentally. The role played in the spin dependent tunneling by carrier concentration and magnetic ion content is also studied. 相似文献
4.
Capture γ-ray circular polarization measurements on the Mn(n, γ), Ni(n, γ), Ga(n, γ) and W(n, γ) reactions with polarized neutrons resulted in unambiguous spin assignments for 20 levels, 10 of which confirmed previous assignments. For another 20 levels the number of possible spin values has been reduced. 相似文献
5.
Ⅲ族金属单硫化物因其优越的光电和自旋电子特性而备受关注,实现对其自旋性质的有效调控是发展器件应用的关键.本文采用密度泛函理论系统地研究了GaSe表面Fe原子吸附体系的几何构型及自旋电子特性.Fe/GaSe体系中Fe吸附原子与最近邻Ga,Se原子存在较强的轨道耦合效应,使体系呈现100%自旋极化的半金属性.其自旋极化贡献主要来源于Fe-3d电子的转移及Fe-3d,Se-4p和Ga-4p轨道杂化效应.对于Fe双原子吸附体系,两Fe原子之间的自旋局域导致原本从Fe转移至GaSe的自旋极化电荷量减少,从而费米能级附近的单自旋通道转变为双自旋通道,费米能级处的自旋极化率转变为0.研究结果揭示了Fe_n/GaSe吸附体系自旋极化特性的形成和转变机制,可为未来二维自旋纳米器件的设计与构建提供参考. 相似文献
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We investigated spin-dependent transport in magnetic tunnel junctions made of III-V Ga(1-x)Mn(x)As electrodes and II-VI ZnSe tunnel barriers. The high tunnel magnetoresistance (TMR) ratio up to 100% we observed indicates high spin polarization at the barrier/electrodes interfaces. We found anisotropic tunneling conductance having a magnitude of 10% with respect to the direction of magnetization to linearly depend on the magnetic anisotropy energy of Ga(1-x)Mn(x)As. This proves that the spin-orbit interactions in the valence band of Ga(1-x)M(x)As are responsible for the tunnel anisotropic magnetoresistance (TAMR) effect. 相似文献
8.
Current and Shot Noise in a Quantum Dot Coupled to Ferromagnetic Leads in the Kondo Regime
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Using the Keldysh nonequilibrium Green function technique, we study the current and shot noise spectroscopy of an interacting quantum dot coupled to two ferromagnetic leads with different polarizations in the Kondo regime. General formulas of current and shot noise are obtained, which can be applied in both the parallel (P) and antiparallel (AP) alignment cases. For large polarization values, it is revealed that the behaviour of differential conductance and shot noise are completely different for spin up and spin down configurations in the P alignment case. However, the differential conductance and shot noise have similar properties for different spin configurations in the P alignment case with the small polarization value and in the AP alignment case with any polarization value. 相似文献
9.
A spin-polarized vertical-cavity surface-emitting laser is demonstrated with electrical spin injection from an Fe/Al0.1Ga0.9As Schottky tunnel barrier. Laser operation with a spin-polarized current results in a maximum threshold current reduction of 11% and degree of circular polarization of 23% at 50 K. A cavity spin polarization of 16.8% is estimated from spin-dependent rate equation analysis of the observed threshold reduction. 相似文献
10.
Thurber KR Harrell LE Smith DD 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,162(2):5779-340
We demonstrate one-dimensional nuclear magnetic resonance imaging of the semiconductor GaAs with 170 nm slice separation and resolve two regions of reduced nuclear spin polarization density separated by only 500 nm. This was achieved by force detection of the magnetic resonance, magnetic resonance force microscopy (MRFM), in combination with optical pumping to increase the nuclear spin polarization. Optical pumping of the GaAs created spin polarization up to 12 times larger than the thermal nuclear spin polarization at 5K and 4T. The experiment was sensitive to sample volumes of 50 microm(3) containing approximately 4 x 10(11)71 Ga/Hz. These results demonstrate the ability of force-detected magnetic resonance to apply magnetic resonance imaging to semiconductor devices and other nanostructures. 相似文献
11.
SHEN Chao WANG LiGuo ZHU Hui & ZHENG HouZhi State Key Laboratory for Superlattices Microstructures 《中国科学:物理学 力学 天文学(英文版)》2011,(6)
Photoluminescence (PL) polarization of a spin ensemble was examined over a wide excitation wavelength range from 520 nm to 700 nm and a temperature range from 3.5 K to 300 K after it transfers from a (AlGa)As barrier layer and eventually quenches irradiatively in a GaAs quantum well (QW).A highest PL circular polarization of 30% can be kept at temperatures up to 120 K,while its room temperature value reaches about 17%.It is found that the main features of the optical spin orientation in bulk Al 0.27 Ga 0.73... 相似文献
12.
V.F. Sapega D. Kolovos-Vellianitis A. Trampert 《Journal of magnetism and magnetic materials》2009,321(7):720-722
The effect of ferromagnetic layers on the spin polarization of holes and electrons in ferromagnet-semiconductor superlattices with a fixed Mn δ-layer thickness of 0.11 nm and different GaAs interlayer thicknesses varying in the range from 2.5 to 14.4 nm and a fixed number of periods (40) is studied by means of hot-electron photoluminescence (HPL). Here, our study of the HPL demonstrates that the holes in δ-layers of (Ga,Mn)As DMS occupy predominantly the Mn acceptor impurity band. The width of the impurity band decreases with the increase of the interlayer distance. We also found that an increase in the GaAs interlayer thickness softens the magnetic properties of the ferromagnetic layers as well as reduces the carrier polarization. It is demonstrated that the hole spin polarization in the DMS layers and spin polarization of electrons in nonmagnetic GaAs are proportional to the sample magnetization. 相似文献
13.
Oulton R Greilich A Verbin SY Cherbunin RV Auer T Yakovlev DR Bayer M Merkulov IA Stavarache V Reuter D Wieck AD 《Physical review letters》2007,98(10):107401
A key to ultralong electron spin memory in quantum dots (QDs) at zero magnetic field is the polarization of the nuclei, such that the electron spin is stabilized along the average nuclear magnetic field. We demonstrate that spin-polarized electrons in n-doped (In,Ga)As/GaAs QDs align the nuclear field via the hyperfine interaction. A feedback onto the electrons occurs, leading to stabilization of their polarization due to formation of a nuclear spin polaron [I. A. Merkulov, Phys. Solid State 40, 930 (1998)]. Spin depolarization of both systems is consequently greatly reduced, and spin memory of the coupled electron-nuclear spin system is retained over 0.3 sec at temperature of 2 K. 相似文献
14.
Dimitriev G. S. Sapega V. F. Averkiev N. S. Panaiotti I. E. Ploog K. H. 《Physics of the Solid State》2017,59(11):2262-2267
Physics of the Solid State - The influence of quantum confinement on the spin polarization of holes in ferromagnetic multiple quantum wells based on (Ga,Mn)As diluted magnetic semiconductor has... 相似文献
15.
Electronic and magnetic properties of the bulk Co2Ti1−xFexGa Heusler alloys and Co2Ti0.5Fe0.5Ga (0 0 1) surfaces are studied within the framework of density functional theory using the augmented plane wave plus local orbital (APW+lo) approach. It will be shown that all alloys have the spin polarization of the ideal 100% value except the Co2FeGa alloy with spin polarization about 98%. Co2Ti0.5Fe0.5Ga is an example that is stable against the effects destroying the half-metallicity due to the position of the Fermi energy (EF) in the middle of the minority band gap. The phase diagram obtained by ab-initio atomistic thermodynamics shows that in the higher limit of μGa three surfaces of FeGa, TiGa and TiFeGa are accessible in the Co2Ti0.5Fe0.5Ga alloy but on decreasing μGa, the accessible region gradually moves towards FeGa termination. It is discussed that, at the ideal surfaces, half-metallicity of the alloy is lost, although the TiGa surface keeps high spin polarization (about 95%). 相似文献
16.
Melinte S Freytag N Horvatic M Berthier C Levy LP Bayot V Shayegan M 《Physical review letters》2000,84(2):354-357
Using a "standard" NMR spin-echo technique we determined the spin polarization P of two-dimensional electrons, confined to GaAs quantum wells, from the hyperfine shift of Ga nuclei located in the wells. Concentrating on the temperature ( 0.05 less, similarT less, similar10 K) and magnetic field ( 7 less, similarB less, similar17 T) dependencies of P at Landau level filling factor nu = 1/2, we find that the results are described well by a simple model of noninteracting composite fermions, although some inconsistencies remain when the two-dimensional electron system is tilted in the magnetic field. 相似文献
17.
This work presents an overview of investigations of the nuclear spin dynamics in nanostructures with negatively charged InGaAs/GaAs quantum dots characterized by strong quadrupole splitting of nuclear spin sublevels. The main method of the investigations is the experimental measurements and the theoretical analysis of the photoluminescence polarization as a function of the transverse magnetic field (effect Hanle). The dependence of the Hanle curve profile on the temporal protocol of optical excitation is examined. Experimental data are analyzed using an original approach based on separate consideration of behavior of the longitudinal and transverse components of the nuclear polarization. The rise and decay times of each component of the nuclear polarization and their dependence on transverse magnetic field strength are determined. To study the role of the Knight field in the dynamic of nuclear polarization, a weak additional magnetic field parallel to the optical axis is used. We have found that, only taking into account the nuclear spin fluctuations, we can accurately describe the measured Hanle curves and evaluate the parameters of the electron–nuclear spin system in the studied quantum dots. A new effect of the resonant optical pumping of nuclear spin polarization in an ensemble of the singly charged (In,Ga)As/GaAs quantum dots subjected to a transverse magnetic field is discussed. Nuclear spin resonances for all isotopes in the quantum dots are detected in that way. In particular, transitions between the states split off from the ±1/2 doublets by the nuclear quadrupole interaction are identified. 相似文献
18.
《Current Applied Physics》2018,18(11):1182-1184
The combination of angular spin momentum with electronics is a promising successor to charge-based electronics. The conduction bands in GaAs may become spin-polarized via optical spin pumping, doping with magnetic ions, or induction of a moment with an external magnetic field. We investigated the spin populations in GaAs with x-ray magnetic circular dichroism for each of these three cases. We find strong anti-symmetric lineshapes at the Ga L3 edge indicating conduction band spin splitting, with differences in line width and amplitude depending on the source of spin polarization. 相似文献
19.
Wu R 《Physical review letters》2005,94(20):207201
Using the density functional full-potential linearized augmented plane wave approach, the x-ray absorption and magnetic circular dichroism (XMCD) spectra of Ga(1-x)Mn x As are calculated. Significantly, XMCD of Mn is highly sensitive to the change in environment, and thus can be utilized to characterize impurity distribution. The nature of Mn-induced spin polarization on Ga and As sites, vital for the carrier mediated magnetic ordering, is discussed in light of computational and experimental results. 相似文献
20.
Yamasaki Y Sagayama H Abe N Arima T Sasai K Matsuura M Hirota K Okuyama D Noda Y Tokura Y 《Physical review letters》2008,101(9):097204
The ferroelectric state in an orthorhombic perovskite RMnO3 (R=Gd0.7Tb0.3) was proved by neutron scattering studies to show the cycloidal spin state with the ab-spiral plane and the spin-helicity dependent polarization vector along the a axis, sharing the microscopic origin (inverse Dzyaloshinskii-Moriya interaction) with the more widely observed P||c state (e.g., for R=Tb and Dy) with the bc-spiral plane. The magnetic-field induced polarization flop from P||c to P||a as well known for RMnO3 is thus assigned to the orthogonal flop of the spin spiral plane from bc to ab. 相似文献