Optical measurement of damping in nanomagnet arrays using magnetoelastically driven resonances
Optical measurement of damping in nanomagnet arrays using magnetoelastically driven resonances
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DOI：
10.1088/1361-6463/aa6472
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发表时间：
2017-03
期刊：
影响因子：
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通讯作者：
Y. Yahagi;C. Berk;B. Hebler;S. Dhuey;S. Cabrini;M. Albrecht;H. Schmidt
中科院分区：
文献类型：
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作者：
Y. Yahagi;C. Berk;B. Hebler;S. Dhuey;S. Cabrini;M. Albrecht;H. Schmidt
表面声波（SAW）在周期性纳米磁体阵列中被光激发，并通过磁弹性耦合驱动磁化旋进。在扩展的施加场范围内，这种机械感应磁响应的频率被固定在SAW频率。首先，我们通过对具有不同阻尼和磁弹性耦合强度组合的材料的实验和数值研究表明，这种钉扎共振的场依赖宽度仅取决于有效阻尼αeff。其次，我们推导出一个解析表达式，用于确定αeff从洛伦兹线形的场依赖的傅立叶振幅的共振。我们表明，固有的吉尔伯特阻尼可以确定在高场极限分析多个钉扎共振在不同的应用领域。这表明，尽管存在与非磁性自由度的相互作用，但可以全光学地提取固有阻尼。我们发现阻尼值为0.027，0.028和0.25分别为Ni，Co和TbFe。最后，实验结果的有效性进行了验证与微磁模拟纳入磁弹性耦合，这表明钉扎宽度是不受磁弹性耦合常数超过三个数量级。这一发现对涉及磁弹性效应的自旋电子器件的合理设计具有重要意义。
Surface acoustic waves (SAWs) are optically excited in periodic nanomagnet arrays and drive the magnetization precession via magnetoelastic coupling. The frequency of this mechanically induced magnetic response is pinned at the SAW frequency over an extended range of applied fields. First, we show by experimental and numerical investigation of materials with different combinations of damping and magnetoelastic coupling strengths that the field-dependent width of this pinned resonance depends only on the effective damping αeff. Second, we derive an analytical expression for determining αeff from the Lorentzian lineshape of the field-dependent Fourier amplitude of this resonance. We show that the intrinsic Gilbert damping can be determined in the high field limit by analyzing multiple pinned resonances at different applied fields. This demonstrates that intrinsic damping can be extracted all-optically, despite interactions with nonmagnetic degrees of freedom. We find damping values of 0.027, 0.028 and 0.25 for Ni, Co and TbFe respectively. Finally, the validity of the experimental results is verified by excellent agreement with micromagnetic simulations incorporating the magnetoelastic coupling, which shows that the pinning width is unaffected by the magnetoelastic coupling constant over three orders of magnitude. This finding has implications for the rational design of spintronic devices that involve magnetoelastic effects.