Revisiting the analytical solution of spin-orbit torque switched nanoscale perpendicular ferromagnets

The scaling of magnetic memory into nanometer size calls for a theoretical model to accurately predict the switching current. Previous models show a large discrepancy with experiments in studying the spin-orbit torque switching of the perpendicular magnet. In this work, we observed that the trajectory of magnetization shows a smooth transition during the switching. This contradicts the magnetization dynamics proposed in previous models, which suggest that magnetization first aligns with the spin polarization (\ensuremath{\sigma}) before switching can occur. We demonstrate that aligning magnetization to \ensuremath{\sigma} requires a very large current, resulting in the unsatisfactory fitting between the previous models and experiments. In contrast, the smooth transition permits a lower switching current. Guided by this refined physical picture, we pinpoint the reversal of precession chirality as a pivotal factor for achieving deterministic switching. This insight contributes to the development of an analytical model that shows good alignment with the experimental data. We offer a clearer understanding of the current-induced magnetization switching process, which will benefit the advancements in spin-orbit torque magnetic random-access memory.