Raman studies of magneto-phonon coupling in Co₂SiO₄

Raman spectroscopy, which is sensitive to both lattice vibrations and magnetic excitations, is employed to investigate magneto-phonon coupling in Co₂SiO₄, an orthorhombic antiferromagnet with a Néel temperature T_N ~ 50 K. The majority of observed Raman modes are assigned to phonons, with frequencies and polarization selection rules in quantitative agreement with density functional theory (DFT) calculations. Several modes of Ag and Bg​ symmetry exhibit pronounced linewidth narrowing and frequency shifts below T_N. Analysis of these temperature-dependent signatures in conjunction with mode eigenvectors provides microscopic insight into the magneto-elastic interactions. On the other hand, a subset of higher-energy modes displays significant deviations from DFT predictions, presumably due to strong interactions, complicating symmetry classification and peak assignment. While similar peaks were reported to violate selection rules in the Fe-based analog of this structure, the temperature-dependence we observed across T_N provided an experimental anchor for comparing several scenarios. Moreover, a splitting of a Bg​ mode emerges in the antiferromagnetic phase, with one branch potentially attributable to a magnetic excitation.