Wang Zilu, Cheng Houyi, Shi Kewen, Liu Yang, Qiao Junfeng, Zhu Daoqian, Cai Wenlong, Zhang Xueying, Eimer Sylvain, Zhu Dapeng, Zhang Jie, Fert Albert, Zhao Weisheng
Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China.
Nanoscale. 2020 Jul 23;12(28):15246-15251. doi: 10.1039/d0nr02762f.
Spin orbit torque (SOT) has drawn widespread attention in the emerging field of magnetic memory devices, such as magnetic random access memory (MRAM). To promote the performance of SOT-MRAM, most efforts have been devoted to enhance the SOT switching efficiency by improving the damping-like torque. Recently, some studies noted that the field-like torque also plays a crucial role in the nanosecond-timescale SOT dynamics. However, there is not yet an effective way to tune its relative amplitude. Here, we experimentally modulate the field-like SOT in W/CoFeB/MgO trilayers through tuning the interfacial spin accumulation. By performing spin Hall magnetoresistance measurement, we find that the CoFeB with enhanced spin dephasing, either generated from larger layer thickness or from proper annealing, can distinctly boost the spin absorption and enhance the interfacial spin mixing conductance Gr. While the damping-like torque efficiency increases with Gr, the field-like torque efficiency is found to decrease with it. The results suggest that the interfacial spin accumulation, which largely contributes to the field-like torque, is reduced by higher interfacial spin transparency. Our work shows a new path to further improve the performance of SOT-based ultrafast magnetic devices.
自旋轨道矩（SOT）在磁存储器件这一新兴领域引起了广泛关注，如磁性随机存取存储器（MRAM）。为了提升SOT-MRAM的性能，大部分努力都致力于通过提高类阻尼转矩来增强SOT开关效率。最近，一些研究指出，类场转矩在纳秒时间尺度的SOT动力学中也起着关键作用。然而，目前尚无有效的方法来调节其相对幅度。在此，我们通过调节界面自旋积累，对W/CoFeB/MgO三层膜中的类场SOT进行了实验调制。通过进行自旋霍尔磁电阻测量，我们发现，无论是由于更大的层厚还是适当的退火而产生的自旋退相增强的CoFeB，都能显著提高自旋吸收并增强界面自旋混合电导Gr。虽然类阻尼转矩效率随Gr增加，但类场转矩效率却随Gr降低。结果表明，对类场转矩有很大贡献的界面自旋积累会因更高的界面自旋透明度而减少。我们的工作为进一步提升基于SOT的超快磁器件的性能开辟了一条新途径。
