Impact of the spin-phonon interaction on the phonon properties of multiferroic hexagonal RMnO₃ thin films.

The phonon properties of multiferroic hexagonal RMnO₃ thin films are studied based on a microscopic model including anharmonic spin-phonon interactions. We obtain an anomaly near the magnetic phase transition temperature T(N) which can be attributed to the magnetoelectric nature of RMnO₃ and a strong spin-phonon interaction. The size and surface effects on the phonon properties are discussed. It is demonstrated that the phonon energies can be larger or smaller for different substrates or doping ions, whereas their damping is always enhanced. The influence of an external magnetic field on the phonon properties is observed.