Probing Defects and Spin-Phonon Coupling in CrSBr via Resonant Raman Scattering

Understanding the stability limitations and defect formation mechanisms in 2D magnets is essen- tial for their utilization in spintronic and memory technologies. Here, we correlate defects in mono- to multilayer CrSBr with their structural and vibrational properties. We use resonant Raman scattering to reveal distinct vibrational defect signatures. In pristine CrSBr, we show that bromine atoms mediate vibrational interlayer coupling, allowing for distinguishing between surface and bulk defect modes. We show that environmental exposure causes drastic degradation in monolayers, with intralayer defects forming more readily in monolayers. Through deliberate ion irradiation, we tune the formation of defect modes, which we show are strongly polarized and resonantly enhanced, reflecting the quasi-1D electronic character of CrSBr. Overall, we present a structural and vibrational study of defective CrSBr, demonstrate the air stability above the monolayer threshold, and provide further insight into the quasi-1D physics present, creating crucial understanding for defect engineering of magnetic textures.