The Raman scattering in relaxor ferroelectrics

The Raman spectra of the relaxer ferroelectrics in the single crystals PbMg 1/3Nb2/3O3(PMN), PbMg1/3Ta2/3O3 (PMT), PbZn1/3Nb2/3O3(PZN) and PbNi1/3Nb2/3 O3 (PNN) have been measured in the frequency range up to 1000 cm(-1) and in the temperature range between 100 K and 773 K. it was found that only in t he PZN which exhibits the rhombohedral phase in the low temperature range, the spectra in the X(ZZ)Y and X(ZX)Y geometries are almost the same. We fou nd that there are two modes at 50 cm(-1) and 790 cm(-1) in common in the al l samples investigated.