Field-free spin-orbit torque switching in orthogonal magnetization configuration with interlayer DMI and tilted perpendicular magnetic anisotropy axes

Spin-orbit torque (SOT) has garnered significant attention for its ability to drive rapid and efficient magnetization switching, making it a promising candidate for future non-volatile memory solutions such as SOTmagnetic random access memory (MRAM). However, conventional SOT-driven magnetization switching typically requires an in-plane magnetic field to assist the process, posing practical challenges for its widespread application. Recently, the approach of using interlayer antiferromagnetic coupling and a tilted perpendicular magnetic anisotropy (PMA) axis to achieve field-free SOT switching in T-type structures has been studied. Building upon the foundational research, we report a novel approach to achieve field-free switching. We consider a configuration of orthogonal magnetizations comprising a perpendicular layer with a tilted magnetic anisotropy easy axis and an in-plane layer, coupled through interlayer Dzyaloshinskii-Moriya interaction (DMI). Through dynamical simulations, we observe four different magnetization precession behaviors occurring in two magnetic layers, which depend on the interlayer DMI strength, the tilt angle of the PMA axes, and the current. With a small current, the magnetization of the PMA layer cannot be switched. Applying an appropriate current, the perpendicular layer can coherently switch in a one-step or two-step switching mode with the in-plane layer without the need for external assisting fields. And it can be controlled by adjusting the interlayer DMI and the tilt of the PMA axes. This novel scheme presents a potential pathway towards practical applications of SOT devices in the future.