Lattice dynamics and spin–phonon interactions in multiferroic RMn2O5RMn2O5: Shell model calculations

The results of the shell model lattice dynamics calculations of multiferroic RMn2O5RMn2O5 materials (space group Pbam  ) are reported. Theoretical even-parity eigenmode frequencies are compared with those obtained experimentally in polarized Raman scattering experiments for R=Ho,DyR=Ho,Dy. Analysis of displacement patterns allows to identify vibrational modes which facilitate spin–phonon coupling by modulating the Mn–Mn exchange interaction and provides explanation of the observed anomalous temperature behavior of phonons.