All-electrical manipulation of magnetization in magnetic tunnel junction via spin–orbit torque

Besides spin-transfer torque, spin–orbit torque (SOT) provides us with another electrical way for developing magnetic random access memory (MRAM) based on magnetic tunnel junctions (MTJs). By using a CoFeB/Ta/CoFeB T-type magnetic structure as a synthetic free layer, we have realized a magnetic-field-free MTJ switchable by SOT. In the T-type structure, an in-plane CoFeB layer is coupled to a perpendicular CoFeB layer via a Ta spacer. The spacer layer not only mediates exchange coupling but also generates strong SOT, which drives sharp switching between the low and high resistance states of the MTJ without any applied magnetic fields. This work could provide an efficient way toward realization of field-free SOT-MRAM or logic devices.