Optimizing unconventional trilayer SOTs for field-free switching

The symmetry and magnitude of unconventional spin–orbit torques in ferromagnet/heavy metal/ferromagnet trilayers are investigated. Several spin-generating mechanisms are considered such as the anomalous Hall effect, anisotropic magnetoresistance, the Rashba-Edelstein effect, and the spin Hall effect. Optimal material thicknesses and magnetization configurations for maximizing out-of-plane spin torques for breaking the bilayer symmetry are presented. Furthermore, field-free switching simulations of a perpendicular SOT-MRAM utilizing the optimized trilayer torques are demonstrated, showing improved switching currents compared to another reported trilayer-based device. • We investigate unconventional SOTs in trilayers to identify optimal configurations for achieving field-free switching of perpendicularly magnetized FMs. • The dependence of the out-of-plane SOTs on the FePt magnetization direction, reveals a strong angular dependence of the torque. • The simulation results of our proposed SOT-MTJ configuration suggest a drastic decrease in the required switching current.