Department of Physics, Durham University, Durham, DH1 3LE, United Kingdom.
Sci Rep. 2017 Jul 4;7(1):4569. doi: 10.1038/s41598-017-04088-8.
Heavy metal layers, exemplified by Pt, are known to play a significant role in the magnetization behaviour of thin-film ferromagnets by three distinct mechanisms that can each contribute to the reversal process. These include modifying the local magnetization state via an interfacial Dzyaloshinskii-Moriya interaction (IDMI), enhancement of the damping, via d-d hybridisation and spin-pumping across the interface, and the mediation of the magnetization switching, with the flow of current through a system, via the spin-Hall effect. Here we show for a system with weak interfacial DMI (NiFe/Pt) that the measurement of magnetic field-driven magnetization reversal, mediated by domain wall (DW) motion, is dominated by the enhanced intrinsic damping contribution as a function of the Pt capping layer thickness. But, we also show micromagnetically that the IDMI and damping also combine to modify the domain wall velocity behaviour when the damping is larger. It is also noted that Walker breakdown occurs at lower fields and peak DW velocity decreases in the presence of IDMI. These results highlight the significance of the relative contributions of the damping and the IDMI from the heavy metal layer on the magnetization reversal and provide a route to controlling the DW behaviour in nanoscale device structures.
重金属层，以 Pt 为例，通过三种不同的机制在薄膜铁磁体的磁化行为中起着重要作用，每种机制都可以促进反转过程。这些机制包括通过界面 Dzyaloshinskii-Moriya 相互作用（IDMI）改变局部磁化状态、通过 d-d 杂化和界面自旋泵浦增强阻尼、以及通过自旋霍尔效应通过电流流过系统来介导磁化切换。在这里，我们展示了一个具有弱界面 IDMI（NiFe/Pt）的系统，磁场驱动的磁化反转的测量，通过畴壁（DW）运动来介导，主要取决于 Pt 覆盖层厚度的增强固有阻尼贡献。但是，我们还从微观磁学角度表明，当阻尼较大时，IDMI 和阻尼也会结合起来改变畴壁速度行为。还注意到，在存在 IDMI 的情况下，Walker 击穿发生在较低的场下，峰值 DW 速度降低。这些结果强调了重金属层的阻尼和 IDMI 的相对贡献对磁化反转的重要性，并为控制纳米级器件结构中的 DW 行为提供了一种途径。
