Probing Short‐Range Correlations in the van der Waals Magnet CrSBr by Small‐Angle Neutron Scattering

Abstract

The layered metamagnet CrSBr offers a rich interplay between magnetic, optical, and electrical properties that can be extended down to the two‐dimensional (2D) limit. Despite the extensive research regarding the long‐range magnetic order in magnetic van der Waals materials, short‐range correlations have been loosely investigated. By using small‐angle neutron scattering (SANS) the formation of short‐range magnetic regions in CrSBr with correlation lengths that increase upon cooling up to ≈3 nm at the antiferromagnetic ordering temperature (T N  ≈ 140 K) is shown. Interestingly, these ferromagnetic correlations start developing below 200 K, i.e., well above T N. Below T N, these correlations rapidly decrease and are negligible at low‐temperatures. The experimental results are well‐reproduced by an effective spin Hamiltonian, which pinpoints that the short‐range correlations in CrSBr are intrinsic to the monolayer limit, and discard the appearance of any frustrated phase in CrSBr at low‐temperatures within the experimental window between 2 and 200 nm. Overall, the obtained results are compatible with a spin freezing scenario of the magnetic fluctuations in CrSBr and highlight SANS as a powerful technique for characterizing the rich physical phenomenology beyond the long‐range order paradigm offered by van der Waals magnets.