Positive spin Hall magnetoresistance in single-crystalline Pt/CoO(001) bilayers

Abstract

The spin Hall magnetoresistance (SMR) effect in single-crystalline Pt/CoO(001) bilayers has been systematically investigated. X-ray magnetic linear dichroism measurements prove that CoO antiferromagnetic (AFM) spins can be switched into the direction orthogonal to the applied field. We find the SMR signal is comprised of two components related to either the switching of CoO AFM N\'eel order or the applied strong field effect. Both SMR components show a ``positive'' angular dependence with ${R}_{\ensuremath{\parallel}}>{R}_{\ensuremath{\perp}}$, while ${R}_{\ensuremath{\parallel}}\phantom{\rule{4pt}{0ex}}({R}_{\ensuremath{\perp}})$ is defined as the resistance with the applied in-plane field parallel (perpendicular) to the current. The observed positive SMR is mainly attributed to the uncompensated spins at the Pt/CoO interface, instead of the CoO AFM spins. Our study may attract a great deal of interest to understand the complicated SMR effect in AFM spintronics materials.