Room-temperature high spin-orbit torque due to quantum confinement in sputtered BiSe films.

The spin-orbit torque (SOT) that arises from materials with large spin-orbit coupling promises a path for ultralow power and fast magnetic-based storage and computational devices. We investigated the SOT from magnetron-sputtered BiSe thin films in BiSe/CoFeB heterostructures by using d.c. planar Hall and spin-torque ferromagnetic resonance (ST-FMR) methods. Remarkably, the spin torque efficiency (θ) was determined to be as large as 18.62 ± 0.13 and 8.67 ± 1.08 using the d.c. planar Hall and ST-FMR methods, respectively. Moreover, switching of the perpendicular CoFeB multilayers using the SOT from the BiSe was observed at room temperature with a low critical magnetization switching current density of 4.3 × 10 A cm. Quantum transport simulations using a realistic sp tight-binding model suggests that the high SOT in sputtered BiSe is due to the quantum confinement effect with a charge-to-spin conversion efficiency that enhances with reduced size and dimensionality. The demonstrated θ, ease of growth of the films on a silicon substrate and successful growth and switching of perpendicular CoFeB multilayers on BiSe films provide an avenue for the use of BiSe as a spin density generator in SOT-based memory and logic devices.