Field-Free Spin-Orbit Torque Switching from Geometrical Domain-Wall Pinning

Spin-orbit torques, which utilize spin currents arising from the spin-orbit coupling, offer a novel method for the electrical switching of the magnetization with perpendicular anisotropy. However, the necessity of an external magnetic field to achieve deterministic switching is an obstacle for realizing practical spin-orbit torque devices with all-electric operation. Here, we report field-free spin-orbit torque switching by exploiting the domain-wall motion in an anti-notched microwire with perpendicular anisotropy, which exhibits multidomain states stabilized by the domain-wall surface tension. The combination of spin-orbit torque, Dzyaloshinskii-Moriya interactions, and domain-wall surface-tension-induced geometrical pinning allows the deterministic control of the domain wall and offers a novel method to achieve a field-free spin-orbit torque switching. Our work demonstrates the proof of concept of a perpendicular memory cell that can be readily adopted in three-terminal magnetic memory.