Ultrahigh Spin-Orbit Torque Efficiency at Spin Reorientation Transition State in Pt/Co Multilayer

Current-induced spin-orbit torques (SOTs) in heavy metal/ferromagnet (HM/FM) systems have attracted considerable attention due to the efficient manipulation of the magnetization [1]. To accelerate the application of the SOT spintronic devices into the next generation logic computing and beyond, intensive efforts have been made to explore new materials and mechanisms of SOT. Of particular technological promises are the HMs with a large spin Hall angle θ SH. Pt/Co bilayers/alloys present ultralow resistivity at ~30 μΩ cm [2], and an enhanced interfacial spin transparency, and thereby strengthen efficiency of the damping-like spin-orbit torque arising from the spin Hall effect in Pt [3]. Researchers concluded that Pt/Co multilayers show great potential for improving the thermal stability and efficient writability. However, it remains undetermined as to how the ferromagnetic thin layer Co modulates the SOTs from HM Pt layers.