Spin-Phonon Coupling and Magnetic Ordering in Layered CrPS4.

Magnetism in van der Waals (vdW) materials offers a platform for exploring dimensionality-tuned magnetic ordering and distinct spin-phonon coupling. Among such materials, CrPS4 stands out as an air-stable A-type antiferromagnet with a Néel temperature of 36 K. Here, we investigate the evolution of phonon modes influenced by magnetic ordering in CrPS4 across varying temperatures and layer thicknesses by using Raman spectroscopy, supported by theoretical calculations. Due to weak interlayer coupling, the thickness-dependent changes in phonon frequencies are negligible (<0.5 cm-1). Notably, anomalous temperature-dependent behavior of the nominally non-magnetic P-S rocking mode reveals its coupling to Cr-S-Cr super-exchange pathways, indicating a strong spin-phonon interaction in CrPS4. The observed magnetic order and spin-phonon interactions remain robust across different thicknesses, with coupling strengths comparable to those of other vdW magnets. Magneto-crystalline anisotropy, metamagnetic transitions, and strong spin-phonon coupling highlight CrPS4 as a promising candidate for integration into vdW heterostructures, offering potential for next-generation magnetic device applications.