Coherent Subnanosecond Switching of Perpendicular Magnetization by the Fieldlike Spin-Orbit Torque without an External Magnetic Field

We theoretically study the influence of a predominant fieldlike spin-orbit torque on the magnetization switching of small devices with a uniform magnetization. We show that for a certain range of ratios (0.23-0.55) of the Slonczewski torque to the fieldlike torque, it is possible to deterministically switch the magnetization without requiring any external assist field. A precise control of the pulse length is not necessary, but the pulse edge sharpness is critical. The proposed switching scheme is numerically verified by micromagnetic simulations to be effective in devices. Switching without any external assist field is of great interest for the application of spin-orbit torques to magnetic memories.