Magnetic scattering and spin-orbit coupling induced magnetoresistance in nonmagnetic heavy metal and magnetic insulator bilayer systems

Abstract

We report on the experimental study of the angular dependent magnetoresistance (MR) of heavy metal/ferromagnetic insulator bilayer structures. Through altering the relative composition in heavy metal $\mathrm{P}{\mathrm{t}}_{\ensuremath{\delta}}\mathrm{T}{\mathrm{a}}_{1--\ensuremath{\delta}}$ alloy, we continuously tune its spin Hall angle from positive, crossing zero, and to negative and study its impact on the MR. Most notably, both spin Hall effect and MR disappear simultaneously in $\mathrm{P}{\mathrm{t}}_{0.32}\mathrm{T}{\mathrm{a}}_{0.68}$ (3 nm)/YIG when the effective spin Hall angle vanishes, evidencing the essential role of spin-orbit coupling in heavy metal for the MR. By introducing Fe impurities, we further identify that magnetic scattering is also essential to induce the MR in Pt/Fe-doped $\mathrm{Si}{\mathrm{O}}_{2}$ at large magnetic field, where the MR ratio increases monotonically with doping level.