Enhanced spin-orbit torque switching in perpendicular multilayers via interfacial oxygen tunability

Spin-orbit torque (SOT) offers a promising pathway to electrically manipulate magnetization in perpendicular multilayers, but the ultrahigh current density required for SOT switching limits its applications. Here, we report that field-free SOT switching is achieved in perpendicular Ta/CoFeB/MgO multilayers by inserting ultrathin Mg or Hf layers. A critical current density of 1.18 × 107 A/cm2 is obtained in Ta/CoFeB/Mg(0.1 nm)/MgO multilayers for field-free SOT switching, which is 42% lower than that in the Ta/CoFeB/MgO sample. The results demonstrate that the enhanced SOT switching efficiency is determined by a modified Rashba interface induced by interfacial orbital hybridization due to the presence of an ultrathin inserted layer. Furthermore, SOT exhibits a significant dependence on the interfacial structure, especially the interfacial oxygen content. Our findings provide an effective insight into the interfacial manipulation of SOT-based spintronic devices.