Determining key spin-orbitronic parameters by means of propagating spin waves

Abstract

We characterize spin wave propagation and its modification by an electrical current in Permalloy(Py)/Pt bilayers with Py thickness between 4 and 20 nm. First, we analyze the frequency non-reciprocity of surface spin waves and extract from it the interfacial Dzyaloshinskii-Moriya interaction constant $D_s$ accounting for an additional contribution due to asymmetric surface anisotropies. Second, we measure the spin-wave relaxation rate and deduce from it the Py/Pt spin mixing conductance $g_{eff}^{\uparrow \downarrow }$. Last, applying a \textit{dc} electrical current, we extract the spin Hall conductivity ${\sigma }_{SH}$ from the change of spin wave relaxation rate due to the spin-Hall spin transfer torque. We obtain a consistent picture of the spin wave propagation data for different film thicknesses using a single set of parameters $D_s=0.25$ pJ/m, $g_{eff}^{\uparrow \downarrow }=3.2\times 10^{19}$ m${}^{-2}$ and ${\sigma }_{SH}=4\times 10^5$ S/m.