Sub-nanosecond in-plane magnetization switching induced by field-like spin-orbit torques from ferromagnets

Abstract: Spin-orbit torques (SOTs) generated in SOT-material/ferromagnet structures are classified as damping-like (DL) and field-like (FL) torques for current-driven magnetization switching. It is well known that both DL- and FL-SOTs originate from the SOT-material and DL-SOT dominates the current-driven switching process while FL-SOT contributes limitedly, resulting in an incubation time (several nanoseconds) during collinear magnetization switching with the spin polarization because of the DL attributes. Here we report a FL-SOT originated from the ferromagnet, different from the origin of DL-SOT, and demonstrate that it dominates the collinear magnetization switching. We show that the FL-SOT and resultant collinear switching can be modulated, one order of magnitude and sign reversal, by controlling the ferromagnet. Because of no incubation time and higher charge-to-spin efficiencies in the FL switching, we further show that the switching time can be down to 200 ps with one order lower critical switching current density compared to DL switching. These results indicate that the FL switching may provide a practical solution for magnetic memory in speed-priority cache applications.