Spin mixing conductance and spin magnetoresistance of the iridate/manganite interface

$\mathrm{SrIr}{\mathrm{O}}₃/{\mathrm{La}}_0.7{\mathrm{Sr}}_0.3\mathrm{Mn}{\mathrm{O}}₃$ heterostructure including contact of $3d\ensuremath{-}5d$ materials with strong spin-orbit interaction in $\mathrm{SrIr}{\mathrm{O}}₃$ was fabricated by rf magnetron sputtering at high temperature. The epitaxial growth of the thin films in heterostructure by a cube-on-cube mechanism was confirmed by x-ray diffraction and transmission electron microscopy analysis. We present results of experimental studies of spin current and spin mixing conductance of the heterostructures measured under spin pumping at ferromagnetic resonance in wide-frequency band 2--20 GHz. Taking into account the contribution of anisotropic magnetoresistance the spin current was estimated as 1/3 of the total response. We show that both real and imaginary parts of spin mixing conductance are valuable for heterostructures with spin-orbit interaction in $\mathrm{SrIr}{\mathrm{O}}₃$. The spin Hall magnetoresistance of the heterostructure was evaluated from angular dependencies of either longitudinal or transverse magnetoresistance measured in planar Hall configuration. The influence of anisotropic magnetoresistance of ${\mathrm{La}}_0.7{\mathrm{Sr}}_0.3\mathrm{Mn}{\mathrm{O}}₃$ film was taken into account as well. The spin Hall angle estimated from measurements of transverse magnetoresistance was found much higher than that obtained for interfaces with often-used spin-orbit interaction material like platinum.