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.
Bibliographical noteFunding Information:
The authors gratefully acknowledge the National Natural Science Foundation of China (Grant Nos 61571023, 61627813), the International Collaboration Project B16001, and the National Key Technology Program of China 2017ZX01032101 for their financial support of this work. The device fabrication was carried out at the University of Minnesota Nanofabrication Centre, which receives partial support from the NSF through the NNIN program. J.-P.W. is acknowledges the Robert F. Hartmann Endowed Chair Professorship.
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