Fast Deterministic Switching in SOT-MRAM with an Additional Magnetic Layer

Magnetoresistive random access memories offer fast switching, high endurance, and long retention. A perpendicular magnetization is required for high memory density. However, spin currents generated by the spin Hall and Rashba-Edelstein effects are only capable of bringing the magnetization in the plane. This hinders any deterministic reversal of perpendicular magnetization as it may relax up or down after the current is turned off.

Deterministic switching of a ferromagnet (FM) on a heavy metal (HM) was achieved when a thin ferromagnet was added below the HM layer [1]. We evaluate the charge and spin transport in a FM/HM/FM structure to reveal additional torques originating from the lower HM/FM interface. Interfacial effects at the HM/FM interfaces are included by considering interfacial scattering from a magnetic exchange and the Rashba spin-orbit coupling-dependent potential [2]. It is demonstrated that in a FM/HM/FM trilayer, additional transversal components of the spin accumulation and the spin current appear. These additional contributions are generated due to the lower FM/HM interface and are absent in an HM/FM bilayer structure. Simulations demonstrate a significant decrease in the switching time of an optimized trilayer compared to that in [1].

1.K. Cai et al., Proc.IEDM, 863 (2022).

2.V.P. Amin and M.D. Stiles, Phys.Rev.B 96, 104419 (2016).