Anomalous behavior of the acoustic phonon velocity and elastic constants of relaxor ferroelectric PbMg1/3Ta2/3O3

Abstract

The behavior of longitudinal acoustic (LA) and transverse acoustic (TA) phonons in a cubic relaxor PbMg1/3Ta2/3O3 (PMT) ferroelectric has been investigated by Brillouin light scattering. Analysis of the temperature dependences of phonon velocity in the temperature range from 50 to 870K has revealed anomalies in the vicinity of the Burns temperature (T B≈570K) for LA phonons and a wide frequency-dependent minimum of the velocities of LA and TA phonons in the same temperature region as the dielectric response anomaly. Using experimental data, temperature dependences of the C11 and C44 elastic constants have been calculated. The elastic constants have been found to be frequency-independent in the gigahertz range. The results obtained are discussed in the framework of modern ideas on the crystalline lattice dynamics of relaxor ferroelectrics. © 2007 IOP Publishing Ltd.