Spin-Orbit Torque Efficiency in Compensated Ferrimagnetic Cobalt-Terbium Alloys

Abstract: Despite the potential advantages of information storage in antiferromagnetically coupled materials, it remains unclear whether one can control the magnetic moment orientation efficiently because of the cancelled magnetic moment. Here, we report spin-orbit torque induced magnetization switching of ferrimagnetic Co1-xTbx films with perpendicular magnetic anisotropy. Current induced switching is demonstrated in all of the studied film compositions, including those near the magnetization compensation point. The spin-orbit torque induced effective field is further quantified in the domain wall motion regime. A divergent behavior that scales with the inverse of magnetic moment is confirmed close to the compensation point, which is consistent with angular momentum conservation. Moreover, we also quantify the Dzyaloshinskii-Moriya interaction energy in the Ta/Co1-xTbx system and we find that the energy density increases as a function of the Tb concentration. The demonstrated spin-orbit torque switching, in combination with the fast magnetic dynamics and minimal net magnetization of ferrimagnetic alloys, promises spintronic devices that are faster and with higher density than traditional ferromagnetic systems.