Magneto-Raman Spectroscopy of Spin Waves in Bulk NiPS₃

NiPS₃ is a van der Waals XY-type antiferromagnet with a Neel temperature of ~155 K. We performed polarization-resolved magneto-Raman measurements on bulk NiPS₃ to probe its spin wave properties. Magnetic field was applied along the a and b crystal axes and perpendicular to the ab plane. We observe two spin wave modes at 9 and 43 cm^-1. The behaviors of these two spin wave modes are different when field is applied along different axes. The magnetic field dependence of the spin wave modes are reproduced in our theoretical calculation. Our results reveal the intriguing spin excitation properties in NiPS₃.