Microscopic parameters of the van der Waals CrSBr antiferromagnet from microwave absorption experiments

Microwave absorption experiments employing a phase-sensitive external resistive detection are performed for a topical van der Waals antiferromagnet CrSBr. The magnetic-field dependence of two resonance modes is measured in an applied field parallel to the three principal crystallographic directions, revealing anisotropies, magnetic transitions, and a strong magnon-magnon coupling in this material. To account for the observed results, we formulate a microscopic spin model with a bi-axial single-ion anisotropy and interplane exchange. Theoretical calculations give an excellent description of full magnon spectra enabling us to precisely determine microscopic interaction parameters for CrSBr.