Picosecond spin-orbit torque switching of ferrimagnets

Spintronics provides an efficient platform for realizing non-volatile memory and logic devices. In these systems, data is stored in the magnetization of magnetic materials, and magnetization is switched in the writing process. In conventional spintronic devices, ferromagnetic materials are used which have a magnetization dynamics timescale of around the nanoseconds, setting a limit for the switching speed. Increasing the magnetization switching speed has been one of the challenges in spintronic research. In this work we take advantage of the ultrafast magnetization dynamics in ferrimagnetic materials instead of ferromagnets, and we use femtosecond laser pulses and a photoconductive Auston switch to create picosecond current pulses for switching the ferrimagnet. By anomalous Hall and magneto-optic Kerr (MOKE) measurement, we demonstrate the robust picosecond SOT driven magnetization switching of ferrimagnetic GdFeCo. The time-resolved MOKE shows more than 50 GHz magnetic resonance frequency of GdFeCo, indicating faster than 20 ps spin dynamics and tens of picosecond SOT switching speed. Our work provides a promising route to realize picosecond operation speed for non-volatile magnetic memory and logic applications.