Magnetic domain states investigated by nonlinear optical spectroscopy in a van der Waals A-type antiferromagnet

Bulk CrSBr is a semiconducting van der Waals magnet that develops A-type in-plane antiferromagnetism (AFM) below T_c = 132 K. It has drawn tremendous attention recently due to its unique properties featuring various magnetic states, tightly bound excitons, long-live magnons, strong magneto-electric and exciton-magnon coupling, as well as its tunability of spin texture through external stimuli such as electric gating and tensile strain. In light of the strong magnetic fluctuations observed near T_c, the formation of AFM domain states below T_c are expected to be intriguing but remain understudied partially due to the lack of effective experimental probes for in-plane AFM. In this presentation, we show our recent effort of investigating magnetism in CrSBr using the interference second harmonic generation rotation ansiostropy (SHG RA) measurements. We will show that two distinct magnetic domain states that are related by a time-reversal operation are observed, and furthermore, that these domain states can be switched between each other through thermal cycles. In addition, we will show the experimental evidence of clear magneto-elastic coupling that the lattice responds critically when the magnetism develops. Finally, we will comment on the impact of such domain states on the excitons in CrSBr.