Anomalous field-induced effects in the sound velocity in lead magnesium niobate probed by micro-Brillouin scattering

Field-induced changes in Brillouin scattering spectra of the PbMg1/3Nb2/3O3 relaxor ferroelectric have been examined in the vicinity of a diffuse phase transition under a dc electric field oriented along the [111] direction. It has been established that the transition into an electric-field-induced ferroelectric phase is accompanied by a step-like anomaly in the sound velocity of the quasilongitudinal acoustic phonon (QLA) propagating along the [110] direction. The changes in QLA phonon velocity at the ferroelectric phase transition were found to be either reversible or irreversible in different regions of the induced ferroelectric phase. The experimental results are compared with E-T phase diagrams. (C) 2004 American Institute of Physics.