Field-free and sub-ns magnetization switching of magnetic tunnel junctions by combining spin-transfer torque and spin-orbit torque

We investigate the magnetization switching via a combination of spin-transfer torque (STT) and spin-orbit torque (SOT). STT and SOT are simultaneously induced by a pulsed current flowing through an in-plane easy-axis magnetic tunnel junction and an underneath Ta/W channel. SOT allows the magnetization to be switched with the sub-ns pulse down to 200 ps and STT eliminates the necessity of an external field. The switching current is much smaller than the case driven solely by STT in the short pulse regime. We also compare the threshold current between two structures having orthogonal (Type Y) and collinear (Type X) magnetic easy axes to the longitudinal direction of the channel and find that the Type X achieves smaller switching current by a factor of 1/4 at 200 ps.