Efficient Spin-Orbit-Torque Switching Assisted by an Effective Perpendicular Field in a Magnetic Trilayer

Creating perpendicular fields by spin-orbit torques (SOTs) is an effective way to realize field-free and highly efficient SOT switching for magnetic films with perpendicular magnetic anisotropy (PMA). Here, (1) using a magnetic trilayer composed of a layer with PMA, a spacer, and a layer with in-plane magnetic anisotropy; and (2) by injecting spin currents with the same polarization into the two magnetic layers, we can generate the desired effective perpendicular field through SOT and further utilize this effective field to assist in field-free SOT switching. The SOT efficiency to produce the perpendicular field reaches $2.1\phantom{\rule{0.2em}{0ex}}\mathrm{Oe}/{10}^{10}\phantom{\rule{0.2em}{0ex}}{\mathrm{Am}}^{\ensuremath{-}2}$. This study can be instructive for designing energy-efficient SOT magnetic random-access memories.