Abstract
Hyper-Raman scattering is used to investigate the vibrations in two prototypical relaxors, PbMg(1/3)Nb(2/3)O(3) and PbMg(1/3)Ta(2/3)O(3) (PMT). First-order scattering from polar modes is clearly observed. Most of the triply-degenerate cubic vibrations are split into doublets and their frequencies compare very well to that of PbTiO(3) in its tetragonal phase. Their shape and scattering intensities are sensitive to the local chemical ordering and ferroelectric distortions. For example, the tendency toward 1: 1 local ordering on the B-site in PMT is clearly evidenced. These results demonstrate the strong potentiality of hyper-Raman scattering as structural probe of complex perovskites.