Optimizing unconventional trilayer SOTs for field-free switching

Abstract

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.