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arXiv 1807.04025cond-mat.mes-hallcond-mat.mtrl-sci
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利用自旋波在铁磁薄膜中的传播研究Dzyaloshinskiii-Moriya相互作用

Probing the Dzyaloshinskii-Moriya interaction via the propagation of spin waves in ferromagnetic thin films

Zhenyu Wang, Beining Zhang, Yunshan Cao, Peng Yan

备注：
10 pages,6 figures,accepted by Physical Review Applied
发表信息：
Phys. Rev. Applied 10, 054018 (2018)
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摘要：

Dzyaloshinskiii-Moriya相互作用（Dzyaloshinskiii-Moriya interaction，简称Dzyaloshinskiii-Moriya）由于其背后的物理机制以及在稳定磁孤子（如磁skyrmion和手征畴壁）中的重要作用而引起了人们的广泛关注。许多实验工作已经致力于探测自旋波的频率差，其中最流行的方法是布里渊光散射光谱（BLS），用于测量具有垂直于面内磁化$\mathbf{m}$的相反波矢量$\pm\mathbf{k}$的自旋波的频率差。然而，这样的技术不适用于$\mathbf{k}\parallel\mathbf{m}$的情况，因为那时自旋波互易性被恢复。对于窄磁条，由于光的空间分辨率限制，使用BLS测量磁感应强度也是困难的。为了填补这些空白，我们建议通过自旋波在铁磁薄膜中的传播来探测自旋波。我们证明了双折射能引起自旋波群速度与$\pm\mathbf{k}\parallel\mathbf{m}$的非共线性。在具有不同DMIs的异质磁性薄膜中，在适当的条件下，自旋波在界面处出现负折射。这些发现使我们能够通过测量两个自旋波光束之间的角度与$\pm\mathbf{k}\parallel\mathbf{m}$在均匀的薄膜和通过测量的入射角和负折射角在异质薄膜中的量子化强度。对于窄磁条，我们提出了一个通过非线性三磁振子过程确定磁振子强度的非定域方案。我们实施理论计算和微磁模拟来验证我们的想法。所得结果对今后的自旋波自旋电子学器件的设计和自旋波自旋电子学器件的测量具有一定的参考价值。

英文摘要：

The Dzyaloshinskii-Moriya interaction (DMI) has attracted considerable recent attention owing to the intriguing physics behind and the fundamental role it played in stabilizing magnetic solitons, such as magnetic skyrmions and chiral domain walls. A number of experimental efforts have been devoted to probe the DMI, among which the most popular method is the Brillouin light scattering spectroscopy (BLS) to measure the frequency difference of spin waves with opposite wave vectors $\pm\mathbf{k}$ perpendicular to the in-plane magnetization $\mathbf{m}$. Such a technique, however, is not applicable for the cases of $\mathbf{k}\parallel\mathbf{m}$, since the spin-wave reciprocity is recovered then. For a narrow magnetic strip, it is also difficult to measure the DMI strength using BLS because of the spatial resolution limit of lights. To fill these gaps, we propose to probe the DMI via the propagation of spin waves in ferromagnetic films. We show that the DMI can cause the non-collinearity of the group velocities of spin waves with $\pm\mathbf{k}\parallel\mathbf{m}$. In heterogeneous magnetic thin films with different DMIs, negative refractions of spin waves emerge at the interface under proper conditions. These findings enable us to quantify the DMI strength by measuring the angle between the two spin-wave beams with $\pm\mathbf{k}\parallel\mathbf{m}$ in homogeneous film and by measuring the incident and negative refraction angles in heterogeneous films. For a narrow magnetic strip, we propose a nonlocal scheme to determine the DMI strength via nonlinear three-magnon processes. We implement theoretical calculations and micromagnetic simulations to verify our ideas. The results presented here are helpful for future measurement of the DMI and for designing novel spin-wave spintronic devices.

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