Koopmans B, Ruigrok J J M, Longa F Dalla, de Jonge W J M
Department of Applied Physics, Center for NanoMaterials (cNM) Eindhoven University of Technology, The Netherlands.
Phys Rev Lett. 2005 Dec 31;95(26):267207. doi: 10.1103/PhysRevLett.95.267207. Epub 2005 Dec 27.
We present a microscopic model that successfully explains the ultrafast equilibration of magnetic order in ferromagnetic metals at a time scale tau(M) of only a few hundred femtoseconds after pulsed laser excitation. It is found that tau(M) can be directly related to the so-called Gilbert damping factor sigma that describes damping of GHz precessional motion of the magnetization vector. Independent of the spin-scattering mechanism, an appealingly simple equation relating the two key parameters via the Curie temperature T(C) is derived, tau(M) approximately c(0)h/k(B)T(C)sigma, with h and k(B) the Planck and Boltzmann constants, respectively, and the prefactor c(0) approximately 1/4). We argue that phonon-mediated spin-flip scattering may contribute significantly to the sub-ps response.
我们提出了一个微观模型，该模型成功解释了铁磁金属中磁序在脉冲激光激发后仅几百飞秒的时间尺度τ(M)内的超快平衡。研究发现，τ(M)可以直接与描述磁化矢量GHz进动运动阻尼的所谓吉尔伯特阻尼因子σ相关。与自旋散射机制无关，通过居里温度T(C)推导出了一个将这两个关键参数联系起来的非常简单的方程，τ(M)≈c(0)h/k(B)T(C)σ，其中h和k(B)分别为普朗克常数和玻尔兹曼常数，前置因子c(0)≈1/4 。我们认为，声子介导的自旋翻转散射可能对亚皮秒响应有显著贡献。
