Field-free spin–orbit switching of canted magnetization in Pt/Co/Ru/RuO2(101) multilayers

Achieving field-free current-induced switching of perpendicular magnetization is crucial for the advancement of spin–orbit torque magnetic random access memory technology. In our study on the Pt/Co/Ru/RuO2(101) system, we have demonstrated field-free switching via current injection along the RuO2[010] axis. We found that the system features a tilted easy axis, deviating from the out-of-plane orientation toward the RuO2[1¯01] direction. The application of current perpendicular to this tilted axis generates a significant out-of-plane effective field, enabling field-free magnetization switching. Our findings also suggest that fine-tuning the thickness of the Ru layer to change the tilt angle can substantially reduce the critical switching current density. This work offers a promising approach for controlling the tilting magnetization, which is vital for the development of RuO2-based magnetic devices.