Room-temperature intrinsic and extrinsic damping in polycrystalline Fe thin films
Room-temperature intrinsic and extrinsic damping in polycrystalline Fe thin films
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DOI：
10.1103/physrevb.105.174408
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发表时间：
2021-09
影响因子：
3.7
通讯作者：
Shuang Wu;David A. Smith;P. Nakarmi;Anish Rai;M. Clavel;M. Hudait;Jing Zhao;F. Michel;C. Mewes;T. Mewes;S. Emori
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作者：
Shuang Wu;David A. Smith;P. Nakarmi;Anish Rai;M. Clavel;M. Hudait;Jing Zhao;F. Michel;C. Mewes;T. Mewes;S. Emori
我们研究室温磁弛豫多晶铁膜。面外铁磁共振（FMR）测量显示吉尔伯特阻尼参数为$\约$0.0024的Fe膜厚度为4-25 nm，无论其微观结构特性。薄膜微结构的显著不变性强烈表明，室温下多晶金属中的固有吉尔伯特阻尼是纳米级晶粒的局部性质，晶界和薄膜粗糙度的影响有限。相比之下，铁膜的面内FMR线宽表现出明显的非线性频率依赖性，表明存在较强的非本征阻尼。为了拟合我们的面内FMR数据，我们使用了具有两种类型相关函数的颗粒到颗粒双磁振子散射模型，旨在描述薄膜中不均匀性的空间分布。然而，这两个相关函数都不能用物理上合理的参数定量地再现实验数据。我们的研究结果推进的内在吉尔伯特阻尼结构无序的薄膜的基本理解，同时证明需要更深入的研究如何微观结构的无序管理外在阻尼。
We examine room-temperature magnetic relaxation in polycrystalline Fe films. Out-of-plane ferromagnetic resonance (FMR) measurements reveal Gilbert damping parameters of $\approx$ 0.0024 for Fe films with thicknesses of 4-25 nm, regardless of their microstructural properties. The remarkable invariance with film microstructure strongly suggests that intrinsic Gilbert damping in polycrystalline metals at room temperature is a local property of nanoscale crystal grains, with limited impact from grain boundaries and film roughness. By contrast, the in-plane FMR linewidths of the Fe films exhibit distinct nonlinear frequency dependences, indicating the presence of strong extrinsic damping. To fit our in-plane FMR data, we have used a grain-to-grain two-magnon scattering model with two types of correlation functions aimed at describing the spatial distribution of inhomogeneities in the film. However, neither of the two correlation functions is able to reproduce the experimental data quantitatively with physically reasonable parameters. Our findings advance the fundamental understanding of intrinsic Gilbert damping in structurally disordered films, while demonstrating the need for a deeper examination of how microstructural disorder governs extrinsic damping.