Field-free switching of a perpendicular magnetic tunnel junction through the interplay of spin-orbit and spin-transfer torques

Magnetization switching in magnetic tunnel junctions using spin-transfer torque and spin-orbit torque is key to the development of future spintronic memories. However, both switching mechanisms suffer from intrinsic limitations. In particular, the switching current in spin-transfer torque devices needs to be lowered, whereas an external magnetic field is required for spin-orbit torque devices to achieve deterministic switching in perpendicular magnetic tunnel junctions. Here, we experimentally demonstrate field-free switching of three-terminal perpendicular-anisotropy magnetic tunnel junction devices through the interaction between spin-orbit and spin-transfer torques. We show that the threshold current density of spin-orbit torque switching can be reduced by increasing the spin-transfer torque current density, and thus an optimal point for low-power perpendicular magnetic tunnel junction switching can be found by tuning the two current densities. Furthermore, and due to this interplay, low-power switching in two-terminal perpendicular magnetic tunnel junctions without an external magnetic field is also achieved.