Interplay between Optical Emission and Magnetism in the van der Waals Magnetic Semiconductor CrSBr in the Two-Dimensional Limit

The van der Waals semiconductor metamagnet CrSBr offersan idealplatform for studying the interplay between optical and magnetic propertiesin the two-dimensional limit. Here, we carried out an exhaustive opticalcharacterization of this material by means of temperature- and magnetic-field-dependentphotoluminescence (PL) on flakes of different thicknesses down tothe monolayer. We found a characteristic emission peak that is quenchedupon switching the ferromagnetic layers from an antiparallel to aparallel configuration and exhibits a temperature dependence differentfrom that of the peaks commonly ascribed to excitons. The contributionof this peak to the PL is boosted around 30-40 K, coincidingwith the hidden order magnetic transition temperature. Our findingsreveal the connection between the optical and magnetic propertiesvia the ionization of magnetic donor vacancies. This behavior enablesa useful tool for the optical reading of the magnetic states in atomicallythin layers of CrSBr and shows the potential of the design of 2D heterostructureswith magnetic and excitonic properties.