Quasistatic and Pulsed Current-Induced Switching with Spin-Orbit Torques in Ultrathin Films with Perpendicular Magnetic Anisotropy

Spin-orbit interaction derived spin torques provide a means of reversing the magnetization of perpendicularly magnetized ultrathin films with currents that flow in the plane of the layers. A basic and critical question for applications is the speed and efficiency of switching with nanosecond current pulses. Here, we investigate and contrast the quasistatic (slowly swept current) and pulsed current-induced switching characteristics of micrometer scale Hall crosses consisting of very thin ( <1 nm) perpendicularly magnetized CoFeB layers on β-Ta. While complete magnetization reversal occurs at a threshold current density in the quasistatic case, short duration ( ≤ 10 ns) larger amplitude pulses ( ≃ 10 times the quasistatic threshold current) lead to only partial magnetization reversal and domain formation. We associate the partial reversal with the limited time for reversed domain expansion during the pulse.