Thermal Stability of CoFe/Cu/CoFe/IrMn Top Spin Valve

We present a study of thermal stability of the top spin valve with a structure of seed Ta （Snm）/Co75Fe25 （5 nm ） /Cu （2.5 nm） /Co75Fe25 （5 nm ） /Ir20Mn80（12 nm） /cap Ta （8 nm） deposited at room temperature by magnetron sputtering. A vibrating sample magnetometer fixed with a heater was used to record the magnetic hysteresis loops at variational temperatures and x-ray diffraction was performed to characterize the structure of the multilayer. The exchange field Hex and the coercivity of the pinned CoFe layer Hop decrease monotonically with increasing temperature. The coercivity of the free CoFe layer Hcf in the spin valve shows a maximum at 498K. The temperature dependences of Hex, Hop and Hcf have also been discussed.     

Effect of Quantum Point Contact Measurement on Electron Spin State in Quantum Dots

We study the time evolution of two electron spin states in a double quantum-dot system, which includes a nearby quantum point contact （QPC） as a measurement device. We find that the QPC measurement induced decoherence is in the microsecond timescale. We also find that the enhanced QPC measurement will trap the system in its initial spin states, which is consistent with the quantum Zeno effect.     

Spin-Orbit Splitting in Semiconductor Quantum Dots with a Two-Dimensional Ring Model

We present a theoretical study of the energy levels with two-dimensional ring confining potential in the presence of the Rashba spin-orbit interaction. The features of some low-lying states in various strengths of the Rashba spin-orbit interaction are investigated. The Rashba spin-orbit splitting can a/so be influenced by the width of the potential barrier. The computed results show that the spin-polarized electronic states can be more easily achieved in a weakly confined dot when the confinement strength for the Rashba spin-orbit interaction is larger than a critical value.     

Electric Field Control of Interface Related Spin Splitting in Step Quantum Wells

Spin splitting of the Aly Ga1-y As/GaAs/A1x Ga1-x As/A1-y Ga1-y As （x ≠ y） step quantum wells （ Q Ws） has been theoretically investigated with a model that includes both the interface and the external electric field contribution. The overall spin splitting is mainly determined by the interface contribution, which can be well manipulated by the external electric field. In the absence of the electric field, the Rashba effect exists due to the internal structure inversion asymmetry （SIA）. The electric field can strengthen or suppress the internal SIA, resulting in an increase or decrease of the spin splitting. The step QW, which results in large spin splitting, has advantages in applications to spintronic devices compared with symmetrical and asymmetrical QWs. Due to the special structure design, the spin splitting does not change with the external electric field.     

Triple Quantum Dot Molecule as a Spin-Splitter

We propose a spin-splitter composed of triple quantum dots that works due to the Coulomb blockade effect and the charge and spin biases applied on external electron source and drains. The spin biases are applied only on the two drains and give their spin-dependent chemical potentials, which act as the driving forces for electron spin-polarized transport. By tuning the biases and the dots＇ levels, spin-up and spin-down electrons can be simultaneously split or separated from the source into two different drains. We show that such a tunneling process is detectable in terms of the spin accumulations on the dots or the currents flowing through the external leads. The present device is quite simple and realizable within currently existing technologies.     

Spin Relaxation of Electrons in Single InAs Quantum Dots

By using polarization-resolved photoluminescence spectra, we study the electron spin relaxation in single InAs quantum dots （QDs） with the configuration of positively charged excitons X＋ （one electron, two holes）. The spin relaxation rate of the hot electrons increases with the increasing energy of exciting photons. For electrons localized in QDs the spin relaxation is induced by hyperfine interaction with the nuclei. A rapid decrease of polarization degree with increasing temperature suggests that the spin relaxation mechanisms are mainly changed from the hyperfine interaction with nuclei into an electron-hole exchange interaction.     

MgO单晶势垒磁性隧道结的第一性原理计算和实验研究

在MgO单晶势垒磁性隧道结中发现的室温高隧穿磁电阻现象,是近些年自旋电子学以及磁性隧道结磁电阻材料研究中的又一重大突破.本文主要评述和介绍2001年以来MgO单晶势垒磁性隧道结第一性原理计算和实验上的重要进展,以及介绍利用Layer-KKR第一性原理计算方法研究的Fe(001)/MgO/Fe、Fe(001)/FeO/MgO/Fe、Fe(001)/Mg/MgO/Fe、Fe(001)/Co/MgO/Co/Fe和Fe(001)[MgO/Fe/MgO/Fe等基于单晶MgO(001)单势垒及双势垒磁性隧道结材料的电子结构和自旋相关输运性质研究的最新进展.这些第一性原理定量计算的结果,不仅从物理上增强了对MgO单晶势垒磁性隧道结的电子结构和自旋相关输运特性的了解,而且对于研究新型室温磁电阻隧道结材料及其在自旋电子学器件中的广泛应用,具有一定的参考价值.     

La0.7Sr0.3-x□xCoO3(0≤x≤0.2)钴氧化物中锶空位诱导的自旋态转变效应

研究了锶空位对La_0.7Sr_0.3-x_xCoO₃ (0≤x≤0.2)多晶钴氧化物结构、磁性和输运性质的影响.结果表明：随着锶空位浓度x的增大,A位阳离子无序度增大,导致铁磁双交换作用减弱及反铁磁超交换作用增强,两者相互竞争,出现团簇自旋玻璃态;空位浓度超过10%后,Co—O键长迅速减小,导致晶体场劈裂能加大,大部分三价钴离子以低自旋态出现,系统基态为类超顺磁态, 关键词： 空位掺杂 钴氧化物 自旋转变     

正多边形量子环自旋输运的严格解

研究了存在Rashba自旋轨道相互作用的正多边形量子环的自旋输运特性．采用量子网络的典型方法和Landauer-Büttiker电导公式,严格求解了电子通过正多边形量子环的散射问题,并得到了电导的解析表达式．通过数值计算和解析分析,进一步研究了量子环电导随电子波矢和自旋轨道相互作用强度变化的复杂形式,包括源于自旋轨道耦合相互作用的电导零点系列．特别地,还研究了正多边形环的边数趋近于无穷的极限情形,与直接采用圆环模型获得的结果完全一致． 关键词： Rashba自旋-轨道相互作用 量子网络 量子输运     

Sherrington-Kirkpatric自旋玻璃模型的非平衡态性质

通过动力学蒙特卡罗模拟对Sherrington-Kirkpatric （SK）自旋玻璃模型进行研究. 结果表明,弱场下自旋玻璃的磁化率在转变点非常陡峭,而比热容则呈现比较宽的转变. 同时,也成功地模拟了自旋玻璃体的年龄效应和记忆效应. 通过模拟发现,不同的弛豫时间对系统的能量影响很大,这直接导致了年龄效应和记忆效应;各向同性的SK模型不能给出实验中的交换偏移现象. 关键词： 自旋玻璃 记忆效应 年龄效应 磁化率