Spin current at the $5d-3d$ interface of epitaxial oxide films (brief review)

Experimental studies of the electrophysical and magnetic properties of a heterostructure of complex SrIrO$_3$/La$_{0.7}$Sr$_{0.3}$MnO$_3$ oxides, where a spin current is observed under ferromagnetic resonance conditions, have been reviewed. thin films of $5d$ strontium iridate SrIrO$_3$ with a strong spin–orbit coupling and $3d$ strontium manganite La$_{0.7}$Sr$_{0.3}$MnO$_3$ have been grown epitaxially on a (110) NdGaO$_3$ single-crystal substrate by magnetron sputtering at a high substrate temperature of $7000$–$8000^\circ$C in a mixture of argon and oxygen gases at a total pressure of $0.3$ mbar. The spin mixing conductance of the interface, which has real (Reg$^{\uparrow\downarrow}$) and imaginary (Img$^{\uparrow\downarrow}$) parts, has been determined from the frequency dependences (in the range of $2$–$20$ GHz) of the linewidth and the resonant field of the ferromagnetic resonance of the SrIrO$_3$/La$_{0.7}$Sr$_{0.3}$MnO$_3$ heterostructure. The spin Hall angle $\theta_{\mathrm{SH}}$, which characterizes the efficiency of the conversion of the spin current into an electric current in the presence of the inverse spin Hall effect, has been calculated from the data on the spin magnetoresistance of the SrIrO$_3$/La$_{0.7}$Sr$_{0.3}$MnO$_3$ heterostructure. The spin Hall angle $\theta_{\mathrm{SH}}$ of the SrIrO$_3$/La$_{0.7}$Sr$_{0.3}$MnO$_3$ heterostructure turns out to be significantly larger (by a factor of almost $40$) than that for the Pt/La$_{0.7}$Sr$_{0.3}$MnO$_3$ heterostructure.