Dynamical Properties of Polar Nanoregions of Relaxor Ferroelectric Pb(Ni_1/3Nb_2/3)O₃–0.29PbTiO₃

Abstract

Dynamical properties of the polar nanoregions (PNRs) of a relaxor ferroelectric Pb(Ni 1/3 Nb 2/3 )O 3 –0.29PbTiO 3 single crystal are studied by using Brillouin scattering to elucidate the mechanism of the diffuse phase transition. The temperature dependence of Brillouin scattering shows anomalies at three temperatures: at T d related to the appearance of the PNRs, at T * associated with the growth of the PNRs, and at T f related to the macroscopic structural phase transition; all these temperatures are closely related to the dynamical behavior of the PNRs. The thermal hysteresis around T f in the longitudinal acoustic properties can be interpreted by considering the growth process of the PNRs. From the anomalous acoustic properties, the relaxation time of the polarization fluctuation is evaluated. It is found that the relaxational process responsible for the central peak originates from the polarization fluctuation that is coupled with the longitudinal acoustic mode.