Spin-Orbit-Torque Switching of Ferrimagnets by Terahertz Electrical Pulses

Abstract

In conventional spintronic devices, ferromagnetic materials are used, which have a magnetization dynamics timescale of around nanoseconds, setting a limit for the switching speed. Increasing the magnetization switching speed has been one of the major challenges for spintronic research. In this work we take advantage of the ultrafast magnetic dynamics in ferrimagnetic materials instead of ferromagnets, and we use femtosecond laser pulses and a plasmonic photoconductive switch to create THz electrical pulses for ferrimagnetic switching by spin-orbit torque. By anomalous Hall and magneto-optic Kerr effect (MOKE) measurement, we demonstrate the robust THz-electrical-pulse-driven magnetization switching of ferrimagnetic $\mathrm{Gd}\text{\ensuremath{-}}\mathrm{Fe}\text{\ensuremath{-}}\mathrm{Co}$. The time-resolved MOKE shows more than 50-GHz magnetic resonance frequency of $\mathrm{Gd}\text{\ensuremath{-}}\mathrm{Fe}\text{\ensuremath{-}}\mathrm{Co}$, indicating faster than 20-ps magnetic dynamics. X-ray magnetic circular dichroism demonstrates the antiferromagnetically coupled $\mathrm{Fe}$ and $\mathrm{Gd}$ sublattices. Our work provides a promising route to realize ultrafast operation speed for nonvolatile magnetic memory and logic applications.