Evolution of the nanopolar order in (1-x)PbFe2/3W1/3O3-xPbTiO3 relaxor investigated by Raman and dielectric study

The multiferroic (1-x)PbFe2/3W1/3O3-xPbTiO(3) solid solution with various compositions in the range xepsilon(0, 1) was investigated. The dielectric data analysed using a Landau-type model allow to obtain the temperature dependence of the local order parameter and show that for high x, the extension of the Curie region and the degree of diffuseness of the phase transition is diminished. This indicates a transition from nanopolar order (relaxor) to long range order (ferroelectric) in this system. The evolution of the infrared and Raman spectra describes the changes of the nanopolar order degree with composition and temperature. Anomalies of the intensity, peak position and bandwidth were found in the Curie range of each composition, proving the changes in the nanopolar order associated with the macroscopic shift of the Curie temperatures determined by dielectric data study.