Behavior of Optical Phonons near the Diffuse Phase Transition in Relaxor   Ferroelectric PbMg1/3Ta2/3O3
  Raman scattering in relaxor ferroelectric PbMg1/3Ta2/3O3 (PMT) was investigated in the single crystalline form in the temperature range of 20 - 295 K. Anomalous temperature dependence of the integrated intensity and the Raman line contours were found at the diffuse phase transition. A correlation between the anomalies in the integrated intensities and the dispersion of the dielectric response was observed. The distortions of Raman lines with decreasing temperature are discussed. 
S.G. Lushnikov, S.N. Gvasaliya, and R.S. Katiyar