垂直电流直写自旋转矩型STT-MRAM已经产品化，但仍存在一些制约因素。最近发现，基于面内电流诱导的“自旋轨道转矩（SOT）效应”可用于发展另一种新型电流驱动磁存储器SOT-MRAM。与STT不同，SOT转矩的产生与参考层磁化方向无关，翻转速度快，无需孕育期。同时，其三端式存储器设计使得信号写入和读取路径分开，有效避免了电流写操作对磁性隧道结氧化层的破坏，提高器件寿命。因此，SOT-MRAM引起人们的极大研究兴趣，目前尚处于起步研究阶段。本项目我们将针对这一前沿科学问题开展微磁学和TR-MOKE相结合的研究，探讨面内电流的SOT效应对磁超快动学参数的影响，阐明SOT驱动磁化翻转的物理机制和行为特性；揭示一致进动翻转或是畴壁移动翻转的微观机理及其依赖关系；研究无外磁场辅助的纯SOT驱动磁化翻转优化结构等。我们期望这些研究有助于加深SOT驱动磁动力学的理解，推动SOT-MRAM的发展。

Magnetic random access memories (MRAMs) utilizing perpendicular current-induced spin-transfer torques (STTs) have been commercialized since 2012, however, they still have some unsolved issues which restrict the practical applications. Recent studies demonstrate that an in-plane flowing current can induce spin-orbit torques (SOTs), which provides an alternative and efficient route for the manipulation of magnetization and can be used to develop the new three-terminal SOT-MRAMs. In contrast to STTs, the generation of SOTs is independent of the ferromagnetic reference layer in magnetic tunnel junctions. In this case the SOT torque is orthogonal to the quiescent free layer magnetization, leading to a negligible incubation delay and hence fast switching speed. Another crucial feature is the separation of the read and write current paths in the SOT devices, which avoids electrical stress of the oxide barrier during writing. Based on these advantages, the study of SOT-MRAMs has attracted a great deal of interest. In this project, we will perform a detailed study regarding this important scientific area by using micromagnetic simulations and time-resolved MOKE techniques. We will investigate the influence of SOT effect on the magnetic dynamic parameters and gain a deep insight into the underlying physical mechanism and characteristics of SOT-driven magnetization switching. We will clarify how and why the SOT effect drives magnetization switching, either by coherent rotation or by domain nucleation and propagation. Furthermore, field-free SOT switching will be explored and the optimal SOT device structure will be designed. We expect these studies shall provide some new insights into better understanding of the SOT-driven magnetization dynamics for SOT-MRAM developments.