Domain wall velocity asymmetries driven by saturation magnetization gradients without a Dzyaloshinskii-Moriya Interaction
Domain wall velocity asymmetries driven by saturation magnetization gradients without a Dzyaloshinskii-Moriya Interaction
复制标题
DOI：
10.1016/j.jmmm.2022.169500
复制
发表时间：
2022-05
影响因子：
2.7
通讯作者：
T. L. Staggers;Liyan Jacob;S. Pollard
中科院分区：
文献类型：
--
作者：
T. L. Staggers;Liyan Jacob;S. Pollard
在没有重金属底层的磁性合金和多层膜中发现不对称畴壁速度，引发了由成分不均匀性驱动的大 Dzyaloshinskii-Moriya 相互作用 (DMI) 的说法。然而，这些不均匀性也会引起垂直不均匀的磁特性，这会影响磁畴壁的动态特性。在这项工作中，我们使用微磁模拟来表明，饱和磁化强度的垂直调制可以产生场和电流驱动运动的不对称畴壁速度，与 DMI 的存在非常相似。对于场驱动运动，通过比较不同饱和磁化强度梯度、薄膜厚度和平均饱和磁化强度的速度不对称性，我们表明，由非均匀性产生的有效对称破缺场的大小可以与 DMI 产生的场大小相当。这些效应随着厚度和调制程度而变化，反映了单层材料的最新结果。然而，对于 SOT 驱动的域动力学，域速度不对称性的缩放在很大程度上受到抑制。因此，在非均匀系统中评估 DMI 时需要非常小心。
The discovery of asymmetric domain wall velocities in magnetic alloys and multilayers without a heavy metal underlayer has given rise to claims of a large Dzyaloshinskii-Moriya interaction (DMI) driven by compositional non-uniformities. However, these non-uniformities also give rise to vertically non-uniform magnetic properties which can influence the dynamic properties of domain walls. In this work, we use micromagnetic simulations to show that vertical modulation of the saturation magnetization can give rise to asymmetric domain wall velocities for field and current driven motion, closely resembling the presence of a DMI. For field driven motion, by comparing the velocity asymmetries for varying saturation magnetization gradients, film thicknesses, and average saturation magnetization, we show that the magnitude of effective symmetry breaking field resulting from the non-uniformity can be comparable to those resulting from DMI. These effects scale with thickness and degree of modulation, mirroring recent results in single layer materials. However, the scaling of domain velocity asymmetries is largely suppressed for SOT driven domain dynamics. Therefore, great care needs to be taken when evaluating DMI in non-uniform systems.