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

TL;DR

This study uses propagating spin waves in Py/Pt bilayers to determine key spin-orbitronic parameters, including the Dzyaloshinskii-Moriya interaction, spin mixing conductance, and spin Hall conductivity, across different film thicknesses.

Contribution

It introduces a method to extract multiple spin-orbitronic parameters from spin wave measurements in a single experimental setup.

Findings

Determined the interfacial Dzyaloshinskii-Moriya interaction constant $D_s=0.25$ pJ/m.

Measured the spin mixing conductance $g^{arrowarrow}_{eff} = 3.2 imes 10^{19}$ m$^{-2}$.

Extracted the spin Hall conductivity $\sigma_{SH}=4 imes 10^{5}$ S/m.

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 $g^{\uparrow\downarrow}_{eff}$. 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, $g^{\uparrow\downarrow}_{eff} = 3.2\times 10^{19}$ m$^{-2}$ and $\sigma_{SH}=4\times10^{5}$ S/m.