Angle-resolved polarized Raman scattering on relaxor ferroelectrics with intermediate random fields

The analysis of the local structure formed by random fields in relaxor ferroelectrics is of technical and fundamental importance in understanding the origin of colossal piezoelectricity. We determined the temperature, electric field, and angular dependences of polarized Raman scattering in Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals. The dependence of the intensity of a Raman active mode on the rotation angle of a polarization plane is measured in a paraelectric cubic phase. These angular dependences are calculated theoretically by assuming the local R3m symmetry to compare the experimental data. The applied electric field in a paraelectric cubic phase suppresses the random fields and therefore the change in the ratio of Raman tensor components from the result at zero field is observed. At a sufficiently higher electric field, the angular variation changes perfectly from its zero field behavior. This indicates the appearance of tetragonal symmetry induced by an electric field.