Evidence for thermal mechanisms in laser-induced femtosecond spin dynamics
Evidence for thermal mechanisms in laser-induced femtosecond spin dynamics
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DOI：
10.1103/physrevb.81.174401
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发表时间：
2010-05-01
影响因子：
3.7
通讯作者：
Muenzenberg, M.
中科院分区：
文献类型：
--
作者：
Atxitia, U.;Chubykalo-Fesenko, O.;Muenzenberg, M.
最近的泵浦探测实验，使用强大的飞秒激光和X射线磁性圆二色性开启了一场辩论的起源磁化修改的飞秒时间尺度上。我们在镍中的飞秒光泵浦探测实验和热微磁模型之间显示了定量的一致性，这揭示了一种主要的热退磁机制。由于电子系统中的散射机制，在系统中引入磁波动作为自旋翻转过程。在我们的模型中，Landau-Lifshitz-Bloch方程的宏观自旋（包含统计平均的磁涨落）耦合到电子温度的双温度模型，其参数是从测量的反射率提取。我们发现，退磁和磁化恢复时间减慢的激光泵浦能量密度的增加，并确定纵向弛豫作为所观察到的行为的一个关键因素。
Recent pump-probe experiments using powerful femtosecond lasers and x-ray magnetic circular dichroism have opened a debate on the origin of the magnetization modification on the femtosecond time scale. We show a quantitative agreement between femtosecond optical pump-probe experiments and thermal micromagnetic modeling in nickel, which reveals a predominant thermal demagnetization mechanism. Magnetic fluctuations are introduced in the system as spin-flip processes due to scattering mechanisms in the electron system. In our model the Landau-Lifshitz-Bloch equation for a macrospin (containing the statistically averaged magnetic fluctuations) is coupled to the electronic temperature of the two-temperature model whose parameters are extracted from the measured reflectivity. We show that the demagnetization and the magnetization recovery time slow down as the laser pump fluence is increased and identify the longitudinal relaxation as a key factor for the observed behavior.