All-oxide ferromagnetic resonance and spin pumping with SrIrO3

Abstract

$\mathrm{SrIr}{\mathrm{O}}_{3}$ is a semimetallic complex oxide of interest for spintronic applications due to the large spin-orbit coupling arising from iridium. It has unusual charge transport properties derived from a complex multiband electronic structure, with electron and hole pockets both contributing to conductivity. We report ferromagnetic resonance of $\mathrm{L}{\mathrm{a}}_{0.7}\mathrm{S}{\mathrm{r}}_{0.3}\mathrm{Mn}{\mathrm{O}}_{3}$ and $\mathrm{SrIr}{\mathrm{O}}_{3}$ epitaxial bilayer films on ${(\mathrm{LaAl}{\mathrm{O}}_{3})}_{0.3}{(\mathrm{S}{\mathrm{r}}_{2}\mathrm{AlTa}{\mathrm{O}}_{6})}_{0.7}$ substrates. Anomalous trends in the out-of-plane magnetic anisotropy and Land\'e $g$ factor suggest that orbital magnetism is modified by proximity of $\mathrm{SrIr}{\mathrm{O}}_{3}$ at low temperatures, likely contributing to large (\ensuremath{\sim}fivefold) enhancements in Gilbert damping. However, enhanced Gilbert damping due to spin pumping is also apparent in the temperature range 250--300 K. The effective spin-mixing conductance is evaluated to be ${G}_{\ensuremath{\uparrow}\ensuremath{\downarrow}}^{\mathrm{eff}}\ensuremath{\sim}0.5\ifmmode\times\else\texttimes\fi{}{10}^{14}\phantom{\rule{0.16em}{0ex}}{\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}2}$, and the spin scattering length scale of $\mathrm{SrIr}{\mathrm{O}}_{3}$ is of the order of \ensuremath{\sim}1 nm. Our work demonstrates the delicate interplay of pure spin current with interfacially mediated spin-orbit effects in a complex oxide heterostructure, exploiting temperature as a control parameter, and should be of interest for both spin pumping and understanding the electronic structure of thin film iridates.