Interfacial Tuning of Anisotropic Gilbert Damping
Lin Chen, S. Mankovsky, M. Kronseder, D. Schuh, M. Prager, Dominique Bougeard, H. Ebert, D. Weiß, C. H. Back
Abstract
Tuning of the anisotropic Gilbert damping $\mathrm{\ensuremath{\Delta}}\ensuremath{\alpha}$ has been realized in ultrathin single-crystalline Fe films grown on GaAs (001). A nonmonotonic dependence of $\mathrm{\ensuremath{\Delta}}\ensuremath{\alpha}$ on film thickness $t$ is observed upon varying $t$ about 10 ML ($\ensuremath{\sim}1.4\text{ }\text{ }\mathrm{nm}$). $\mathrm{\ensuremath{\Delta}}\ensuremath{\alpha}$ increases for $16\text{ }\text{ }\mathrm{ML}>t>8.5\text{ }\text{ }\mathrm{ML}$, and then decreases for $8.5\text{ }\text{ }\mathrm{ML}>t>6.5\text{ }\text{ }\mathrm{ML}$ accompanied by a sign reversal of $\mathrm{\ensuremath{\Delta}}\ensuremath{\alpha}$ for $t=6.5\text{ }\text{ }\mathrm{ML}$. The sign reversal of $\mathrm{\ensuremath{\Delta}}\ensuremath{\alpha}$ is captured by first-principle calculations, which show that the anisotropic density of states changes sign upon decreasing $t$. Moreover, ${t}^{\ensuremath{-}1}$ 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.