CoFeB/MgO磁隧道结的低电流密度磁矩翻转特性

Lower-current-density-induced magnetization switching in the CoFeB / MgO based magnetic tunnel junction

基于Landau-Lifshitz-Gilbert-Slonczewski(LLGS)方程,研究平面型Co Fe B/Mg O磁隧道结的磁矩翻转特性.数值计算结果表明,Co Fe B与Mg O间的界面各向异性,可降低磁矩翻转的阈值电流密度,达到106A/cm2量级.固定层磁矩方向和类场自旋转移力矩对自由层磁矩的翻转时间有重要影响.当固定层磁矩与自由层磁矩之间有一个小角度时,可显著加快自由层磁矩翻转.当类场自旋转移力矩与自旋转移力矩之比为负值时,类场自旋转移力矩与自旋转移力矩将促进自由层磁矩翻转;当相应的类场自旋转移力矩与自旋转移力矩之比为正值时,类场自旋转移力矩将阻碍自由层磁矩翻转.该研究可供自旋转移力矩驱动的磁性随机存储器件设计借鉴.

We investigate the magnetization switching properties of in-plane magnetic tunnel junctions based on the Landau-Lifshitz-Gilbert-Slonczewski （LLGS） equation. Numerical results show that a lower magnetization switching current density, which can be decreased down to 10^6 A/cm2, can be achieved in CoFeB/MgO based magnetic tunnel junctions with interfaeial perpendicular anisotropy. In particular, the magnetization orientation of the pinned layer and the field-like spin transfer torque have great effect on the magnetization switching time. A small angle between the magnetization orientations of pinned and free layers can significantly reduce the magnetization switching time.Moreover, when the ratio between the spin torque and the field-like torque takes a negative value, the field-like torque can reduce the magnetization switching time and vice versa. These characteristics can provide a theoretical ba- sis for designing magneto-resistive random access memory driven by spin transfer torque.