Raman signatures of spin-phonon coupling in a self-intercalated van der Waals magnet Mn3Si2Te6

We report the results of Raman spectroscopy on a self-intercalated van der Waals ferrimagnet Mn3Si2Te6. Using polarization-resolved Raman spectroscopy, we identify twelve phonon modes with Eg and A1g symmetries, in agreement with the first principle calculations. Below the ferrimagnetic transition temperature Tc∼ 78 K, we observed a significant deviation of the phonon frequency from the anharmonic model, accompanied by a strong line broadening, indicating a substantial spin-phonon coupling in Mn3Si2Te6. Among twelve phonon modes, this spin-phonon coupling is found to be strong mostly in the out-of-plane vibrational modes. These results highlight the dominant role of the interlayer superexchange interaction in determining the magnetic properties, reflecting the self-intercalated van der Waals structure of Mn3Si2Te6.