We report a large enhancement of spin–orbit torque (SOT) in perpendicular Ta/CoFeB/MgO multilayers with interfacial H+ and O2– ion manipulations. By controlling both H+ and O2– ions at the CoFeB/MgO interface, the switching current density (Jc) is almost half of that for the single O2– ion manipulated sample. Through harmonic measurements, we have found that both dampinglike effective field HD and fieldlike effective field HF are increased for the H+ and O2– ion manipulated samples. Interfacial structural results indicate that the H+ and O2– ion manipulations modulate the interfacial chemistry at the CoFeB/MgO interface, which suppresses the spin reflection and improves the spin absorption in the CoFeB layer. Our results can effectively improve the SOT and provide an effective way to modulate SOT.

The spin–orbit-torque (SOT) consists of dampinglike torque (DLT) and fieldlike torque (FLT), where the combined effects of these two torques need further consideration for efficient SOT switching. Here, the tunable correlation between the DLT and FLT is investigated in Pt/Co/HfO2 multilayers with different annealing temperatures (Ta). With increasing Ta, the FLT decreases monotonously, while both the sign and the magnitude of DLT are changed. Interfacial analysis results reveal that the tunable correlation of them is strongly dependent on the interfacial electron structure between the Co and HfO2 layer. The interfacial charge transfer between the Co, O, and Hf atoms could modify interfacial spin–orbit coupling and the crystal electric field (ECEF), which promotes the interface-generated SOT. This work demonstrates an effective method to tune the correlation of the two SOT components, a desirable feature which will be beneficial for the design of SOT-based devices.

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