Lattice dynamics of Sr2TiO4

Lattice dynamics of Sr2TiO4 is investigated by means of inelastic neutron scattering and Raman scattering experiments. The phonon density of states is experimentally determined by inelastic neutron scattering experiment and all the peaks except the one at 88 cm-1 can be attributed to some optical modes, whereas the peak at 88 cm-1 is probably due to the acoustic phonons at the zone boundary. Raman scattering experiments done at low temperature reveal that the explicit contribution to the anharmonicity from the thermal population of the vibrational levels should be stronger for the high energy A1g mode at about 570 cm-1 than for the other Raman active modes. This contribution increases anomalously with the temperature due to a quartic anharmonic contribution