Enhanced field-free current-induced magnetization switching by interlayer exchange coupling with insulating spacer layer

Abstract

We investigated field-free current-induced perpendicular magnetization switching in Pt/Co/AlOx/Co/Ta structures by varying the thickness of an insulating spacer layer. A field-free spin–orbit torque switching is realized through the antiferromagnetic interlayer exchange coupling (IEC) between the bottom and top Co layers or by premagnetizing the top Co layer. Significant variations in magnetic and electrical properties are ascribed to thickness dependent IEC by changing the insulating spacer layer from 1.0 to 1.9 nm. When the thickness of the spacer layer is 1.6 nm, we found the strongest IEC field of about 300 Oe and optimal field-free current-induced magnetization switching. Micromagnetic simulation validates the existence of the Dzyaloshinskii–Moriya interaction (DMI) effect and the chirality of the domain wall configuration in the stack structures, and the field-free deterministic magnetization switching is mainly induced from DMI and IEC fields.