Magnetic-field-free spin–orbit torque-driven magnetization dynamics in CoFeB/β-W-based nanoelements

Abstract

A full numerical analysis, which takes into account the effects of the spin Hall effect, interfacial Dzyaloshinskii–Moriya interaction, and thermal fluctuations, is carried out in in-plane magnetized CoFeB/MgO/CoFeB/high-resistivity tungsten (β-W) nanoelements. The analysis is focused on the investigation of the underlying mechanisms of magnetic-field-free spin–orbit torque (SOT)-driven magnetization reversal process on subnanosecond time scales. It is found that the magnetization in the free magnetic layer can be electrically toggled between the parallel and antiparallel alignment with respect to the fixed magnetic layer without the assistance of an external magnetic field, in which the out-of-plane canting of the magnetic moments at the element edges plays a significant role in the nucleation and subsequent expansion of the reversed magnetization. Furthermore, the thermally activated magnetization process combined with the SOT effect is found to significantly reduce the effective energy barrier to the magnetization reversal and alter the details of the SOT-driven magnetization process in nanomagnets.