Detecting and switching magnetization of Stoner nanograin in nonlocal spin valve
Detecting and switching magnetization of Stoner nanograin in nonlocal spin valve
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DOI：
10.1103/physrevb.80.094401
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发表时间：
2009-03
影响因子：
3.7
通讯作者：
Hai-Zhou Lu;S. Shen
中科院分区：
文献类型：
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作者：
Hai-Zhou Lu;S. Shen
从理论上研究了非局域自旋阀（NLSV）器件中超小Stoner纳米颗粒的磁化检测和开关。借助于速率方程，可以在相同的基础上对读出磁化的NLSV信号和开关过程进行统一描述。该设置可以被视为通过顺序隧穿将晶粒连接到两个双极引线。在一个引线中，由于NLSV中的自旋注入，自旋向上和自旋向下电子的化学势被分裂。这种分裂（或自旋偏置）对NLSV信号和磁化切换的临界条件至关重要。通过使用标准的自旋扩散方程和参数，从最近的NLSV设备，自旋偏置的幅度估计，并发现足够大的驱动磁化切换的钴纳米颗粒在早期的实验报告。由此提出了在连续隧穿机制中NLSV信号的微观解释，其显示了由于晶粒的超小尺寸而产生的性质。在反转点处的动力学表明，由于用于读出NLSV信号的浮置引线中的电子积累，在反转期间可能存在自旋极化电流而不是预期的纯自旋电流。
The magnetization detection and switching of an ultrasmall Stoner nanograin in a nonlocal spin valve (NLSV) device is studied theoretically. With the help of the rate equations, a unified description can be presented on the same footing for the NLSV signal that reads out the magnetization, and for the switching process. The setup can be viewed as that the grain is connected to two nonmagnetic leads via sequential tunneling. In one lead, the chemical potentials for spin-up and -down electrons are split due to the spin injection in the NLSV. This splitting (or the spin bias) is crucial to the NLSV signal and the critical condition to the magnetization switching. By using the standard spin diffusion equation and parameters from recent NLSV device, the magnitude of the spin bias is estimated and found large enough to drive the magnetization switching of the cobalt nanograin reported in earlier experiments. A microscopic interpretation of NLSV signal in the sequential tunneling regime is thereby raised, which show properties due to the ultrasmall size of the grain. The dynamics at the reversal point shows that there may be a spin-polarized current instead of the anticipated pure spin current flowing during the reversal due to the electron accumulation in the floating lead used for the readout of NLSV signal.