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 G_r. While the damping-like torque efficiency increases with G_r, 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.

中文翻译：

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重金属/铁磁体异质结构中类似场的自旋轨道转矩的调制。

自旋轨道转矩（SOT）在诸如磁性随机存取存储器（MRAM）的磁性存储设备的新兴领域引起了广泛的关注。为了提高SOT-MRAM的性能，已经进行了大部分努力，以通过改善类似阻尼的转矩来提高SOT切换效率。最近，一些研究指出，类似磁场的转矩在纳秒级时标SOT动力学中也起着至关重要的作用。但是，尚没有一种有效的方法来调节其相对振幅。在这里，我们通过调整界面自旋积累实验性地调制W / CoFeB / MgO三层中的场状SOT。通过执行自旋霍尔磁阻测量，我们发现具有更大自旋相移的CoFeB可能是由较大的层厚或适当的退火产生的，摹_[R 。尽管随着G _r的增加，阻尼转矩效率增加，但是，随着转矩的降低，磁场转矩效率降低。结果表明，较高的界面自旋透明度降低了界面自旋的积累，而界面自旋的积累在很大程度上促进了类似磁场的转矩。我们的工作表明了一条进一步改善基于SOT的超快磁器件性能的新途径。