Abstract
A single crystal of the relaxor PbMg1/3Nb2/3O3 is studied by hyper-Raman scattering. The relative scattering intensities obtained for the band near 250 cm-1 in various polarization geometries are fully compatible with hyper-Raman spectroscopy tensor of the F2u zone-center vibrational mode of prototype Pm3¯m Oh 1 cubic perovskite structure. The mode was investigated between room temperature and 775 K, thus covering the range around the Burns temperature Td and the crossover temperature T. At variance with recent anticipations, no softening was observed.