Department of Physics, Technical University of Munich, Munich, Germany.
Department of Chemistry, Ludwig Maximilian University, Munich, Germany.
Phys Rev Lett. 2023 Jan 27;130(4):046704. doi: 10.1103/PhysRevLett.130.046704.
Tuning of the anisotropic Gilbert damping Δα has been realized in ultrathin single-crystalline Fe films grown on GaAs (001). A nonmonotonic dependence of Δα on film thickness t is observed upon varying t about 10 ML (∼1.4 nm). Δα increases for 16 ML>t>8.5 ML, and then decreases for 8.5 ML>t>6.5 ML accompanied by a sign reversal of Δα for t=6.5 ML. The sign reversal of Δα is captured by first-principle calculations, which show that the anisotropic density of states changes sign upon decreasing t. Moreover, t^{-1} dependence of the anisotropic damping indicates the emergence of an anisotropic effective spin mixing conductance according to the theory of spin pumping. The results establish new opportunities for controlling the Gilbert damping and for fundamental studies of magnetization dynamics in reduced dimension.
在 GaAs(001) 上外延生长的超薄单晶 Fe 薄膜中实现了各向异性 Gilbert 阻尼 Δα 的调控。当改变薄膜厚度 t 时，观察到 Δα 随 t 的变化表现出非单调依赖性。当 16 ML>t>8.5 ML 时，Δα 增加，然后当 8.5 ML>t>6.5 ML 时，Δα 减小，同时当 t=6.5 ML 时，Δα 的符号发生反转。第一性原理计算捕捉到了 Δα 的符号反转，表明各向异性态密度在 t 减小时符号发生变化。此外，各向异性阻尼的 t^{-1}依赖性根据自旋泵浦理论表明各向异性有效自旋混合电导的出现。这些结果为控制 Gilbert 阻尼和减少维度中磁化动力学的基础研究提供了新的机会。
