Longitudinal spin current absorption in bilayers composed of ferromagnetic and highly-resistive non-magnetic layers

Abstract

Spin Hall magnetoresistance (SMR) is an intriguing spin-dependent transport phenomenon in bilayers consisting of non-magnetic and magnetic layers. Here, we report on the influence of longitudinal spin current absorption by the magnetic layer on SMR in bilayers composed of Co$_{20}$Fe$_{60}$B$_{20}$ (CoFeB) and epitaxial SrIrO$_{3}$, where SrIrO$_{3}$ is used as a highly-resistive spin current source. We observed a clear SMR signal and an enhancement in the SMR ratio with increasing CoFeB layer thickness, in qualitative agreement with an SMR model that incorporates the spin current absorption. The effective spin Hall angle is corrected from 0.07 to 0.12 with consideration of the spin current absorption, corresponding to a relative correction of ~71%. Our findings highlight the pronounced impact of the spin current absorption by the magnetic layer on the SMR mechanism when employing highly-resistive non-magnetic layer such as SrIrO$_{3}$, as well as other emerging quantum materials.