Optical readout of spin-orbit torque acting on magnetic thin films

Spin-orbit torque (SOT) is the leading technology to achieve low-energy magnetization switching for next-generation nonvolatile memory and logic. In SOT, a charge current applied through a channel with strong spin-orbit coupling produces a transverse spin current that applies a torque to switch an adjacent ferromagnetic layer. In addition to transport measurements, optical measurements can provide unique insights into the SOT switching dynamics because light can directly couple to the magnetic state through magneto-optic Kerr effect (MOKE). In this talk, I will discuss recent progress in using magneto-optic Kerr effect (MOKE) microscopy technique to probe SOT manipulation of both conventional metallic ferromagnets and van der Waals magnets. I also will illustrate the pros and cons of optical readout for quantifying SOT efficiency, in comparison with standard transport measurements such as the second-harmonic Hall technique and spin-torque ferromagnetic resonance (ST-FMR).