External-Field-Free Spin Hall Switching of Perpendicular Magnetic Nanopillar with a Dipole-Coupled Composite Structure

Spin Hall effect (SHE)-induced reversal of perpendicular magnetization has attracted significant interest, due to its potential for low-power memory and logic devices. However, the switching requires an assisted in-plane magnetic field, which hampers its practical applications. Here, a new approach for external-field-free spin Hall switching of a perpendicular nanomagnet is introduced. This approach utilizes a local dipolar field arising from an in-plane biasing layer to assist the switching. Robust switching of a 285 x 95 nm(2) perpendicular CoFeB nanomagnet is demonstrated in the absence of any external magnetic field. Micromagnetic simulation is performed to illustrate the magnetic dynamics of the switching process. Large in-plane compensation field of 135 Oe is obtained in the composite nanodevices, reflecting a strong symmetry-breaking behavior. Compared with other proposed methods for external-field-free spin Hall switching, the dipole-coupled composite structure is compatible with a wide range of spin Hall systems and perpendicular magnetic tunnel junctions, paving a way towards practical spin-orbit torque-based memory and logic applications.