Direct Optical Probing of the Magnetic Properties of the Layered Antiferromagnet CrPS₄

The unusual magnetic properties of van der Waals-type antiferromagnetic semiconductors such as transition metal thiophosphates make them highly attractive for spintronics and optoelectronics. However, a link between the magnetic and optical properties of these materials, required for practical applications, has not yet been established. A combined experimental and theoretical study of magnetic, optical, and structural properties of CrPS₄ samples is reported. It is found that the magnetic-field-dependent circular polarization degree of the photoluminescence is a direct measure of the net magnetization of CrPS₄. Complementary Raman scattering measured as a function of magnetic field and temperature enables the determination of the magnetic susceptibility curve of the material. Experimental results are supported by density functional theory calculations that take as input the lattice parameters determined from temperature-dependent X-ray diffraction measurements. This allows the impact of spin ordering on the spectral position of Raman transitions in CrPS₄ to be explained, as well as the anomalous temperature shifts of some of them. The presented method for all-optical determination of magnetic properties is highly promising for studies of spin ordering and magnetic phase transitions in single- or few-layer samples of magnetic layered materials, for which a poor signal-to-noise ratio precludes reliable neutron scattering or magnetometry measurements.