Magneto-Raman Study of Magnon-Phonon Coupling in Two-Dimensional Ising Antiferromagnetic FePS₃

Recently, the coupling between magnons (quanta of spin waves) and phonons (quanta of lattice vibrations) in two-dimensional (2D) antiferromagnet FePS₃ offers a myriad of applications ranging from spintronic devices to quantum information technologies. However, the reported magnon-phonon coupling in the FePS₃ flake using Raman measurements requires an ultrahigh magnetic field up to 30 T. Here, we investigate the magnon-phonon coupling in FePS₃ by near-resonant magneto-Raman spectroscopy under a relatively small magnetic field (|H₀| ≤ 9 T). Under near-resonant excitation, we find more pronounced coupling effects that are absent in non-resonant excitation: three optical phonons sensitive to the applied magnetic field are resolved, two of which show a frequency anti-crossing coupling with magnon, while the other coupled phonon exhibits only a polarization-coupled character without frequency anti-crossing. Besides, our polarized Raman results also show the polarization transferring between coupled magnon-phonon modes. On the basis of a modified theoretical model, we can well explain the measured Raman spectra.