Temperature Evolution of Atomic Dynamics in Chemically Ordered Lead Scandium Niobate Studied by Inelastic Neutron Scattering

Preliminary results of inelastic neutron scattering in chemically ordered Pb(Sc 1/2 Nb 1 / 2 )O 3 (PSN) are reported. It is shown that neutron spectra, obtained around 220 node in $\left[ {1\bar 10} \right]$ direction, are characterised by intense central peak and broad phonon resonances at all studied temperatures. It has been found that TO in-plane polarised phonons do not demonstrate any softening. On the contrary, clear growth of TO phonon energy was detected for all temperatures. Intensity of the central peak continuously grows on cooling. Observed critical dynamics scenario completely differs from the expected one for relaxor or ferroelectric material. We believe our observations could bring new insights in the understanding of the microscopic origin of the relaxor phenomena.