A central peak in light scattering from the relaxor-type ferroelectric Na 1/2Bi 1/2TiO 3
Abstract
A complex perovskite-type single crystal Na 1/2Bi 1/2TiO 3 (NBT) has been studied by Raman scattering. A broad central component has been revealed to analyze the temperature dependence of its intensity and width for the first time. The central component has features of a relaxation mode with the highest intensity in the intertransition region, so it arises from a critical light scattering on fluctuations of two coupled order parameters. The correlations between the central component behaviour, acoustic anomalies and dielectric response as well as their relation to a model with competing interactions are discussed. It is suggested that the broad central peak component in light scattering is characteristic of the relaxor-type ferroelectrics with a sequence of phase transformation irrespective of whether transitions are really observed as in NBT or whether transitions are frustrated under normal conditions as in PbMg 1/3Nb 2/3O 3 (PMN).