Magnetization dissipation in ferromagnets from scattering theory
Magnetization dissipation in ferromagnets from scattering theory
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DOI：
10.1103/physrevb.84.054416
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发表时间：
2011-04
影响因子：
3.7
通讯作者：
A. Brataas;Y. Tserkovnyak;G. Bauer
中科院分区：
文献类型：
--
作者：
A. Brataas;Y. Tserkovnyak;G. Bauer
铁磁体的磁化动力学通常用 Landau-Lifshitz-Gilbert (LLG) 方程来表示。该方程的电抗部分描述了磁化强度在有效场方面的响应，而耗散部分则由吉尔伯特阻尼张量参数化。我们制定了磁化动力学的散射理论，并通过将电接触连接到铁磁体上，将该描述映射到线性 LLG 方程上。然后反应部分可以用静态散射矩阵来表示。对低频磁化动力学的耗散贡献可以描述为通过时间相关磁化对电子子系统的绝热能量泵送过程。吉尔伯特阻尼张量取决于散射矩阵的时间导数作为磁化方向的函数。根据涨落耗散定理，有效场的涨落也可以用准静态散射矩阵来表示。该理论是针对一般磁化纹理而制定的，并针对单畴进动和畴壁运动进行了计算。我们证明了散射理论的吉尔伯特阻尼与久保形式主义得到的结果相同。
The magnetization dynamics of ferromagnets is often formulated in terms of the Landau-Lifshitz-Gilbert (LLG) equation. The reactive part of this equation describes the response of the magnetization in terms of effective fields, whereas the dissipative part is parametrized by the Gilbert damping tensor. We formulate a scattering theory for the magnetization dynamics and map this description on the linearized LLG equation by attaching electric contacts to the ferromagnet. The reactive part can then be expressed in terms of the static scattering matrix. The dissipative contribution to the low-frequency magnetization dynamics can be described as an adiabatic energy pumping process to the electronic subsystem by the time-dependent magnetization. The Gilbert damping tensor depends on the time derivative of the scattering matrix as a function of the magnetization direction. By the fluctuation-dissipation theorem, the fluctuations of the effective fields can also be formulated in terms of the quasistatic scattering matrix. The theory is formulated for general magnetization textures and worked out for monodomain precessions and domain-wall motions. We prove that the Gilbert damping from scattering theory is identical to the result obtained by the Kubo formalism.