应力调制的自旋转矩临界电流*

摘要

自旋转矩临界电流过大的问题长期以来一直为人们所关注。本文提出，可以通过引入面外应力即引入应力各向异性场来降低退磁场，从而降低自旋转矩的临界电流。本文采用四分量分布式自旋电路模型计算了横向自旋阀由注入端输运到探测端(自由层)的极化电流大小。利用Landau-Lifshitz-Gilbert-Slonczewski方程数值研究了存在应力时，横向自旋阀中自旋转矩引起的自由层磁矩翻转的性质。结果表明，适当选择应力方向可使面外退磁场得到有效补偿，从而显著降低自旋转矩临界电流。另外，随着应力提高和退磁场的减小，磁矩翻转时间也大大减小。%Excessive spin-torque critical current has long been a problem received much attention. In this paper, we suggest that by introducing the out-of-plane stress or the stress anisotropy field, the out-of-plane demagnetizing field can be compensated effectively, and in this way the spin-torque critical current can be reduced. Specifically, the four-component distributed spin-circuit model is used to calculate the polarization current which is transferred from the polarizer to the detector (free layer).The properties of magnetization switching in the free layer of the lateral spin valve are studied under the influence of stress by using the Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation. Results show that, if the stress direction is appropriately selected, the out-of-plane demagnetizing field can be effectively compensated, thereby the spin torque critical current can be significantly reduced. Furthermore, as the stress is increased and the demagnetizing field is reduced, the magnetization reversal time is greatly reduced.