Magnetization dynamics enabling reliable nanosecond-timescale switching through the spin Hall effect

We have recently reported that spin Hall torque can drive magnetic switching that is simultaneously fast and reliable (\textless 10$^{\mathrm{-5}}$ write error rates with 2 ns pulses) in 3-terminal magnetic tunnel junctions (3T-MTJs) with in-plane magnetization [1]. This is in contrast to switching of in-plane 2-terminal MTJs by conventional spin transfer torque (STT), where there are 10's of ns latency times. Here we present a comprehensive elucidation of the switching dynamics in 3T-MTJs obtained through fast-pulse measurements in a variety of material stacks and detailed micromagnetic simulations. We demonstrate that the interaction between the self-generated Oersted field in 3T-MTJs and the micromagnetics of the free layer can lead to reliable sub-nanosecond reversal. We further show through simulations that an artificially reversed Oersted field, which corresponds to the field-like component of spin torque in 2-terminal STT-switched MTJs, leads to undesirable pre-switching dynamics that are highly reminiscent of the latency times in literature. These results establish the in-plane 3T-MTJ as an attractive memory element for applications that do not require ultra-high density, due to its high magnetoresistance read signal, low impedance write path, and fast reliable switching. [1] S. V. Aradhya et al., Nano Lett., 2016, 16 (10), 5987.