Anomalous behavior of acoustic phonon and central peak in Pb[(In1/2Nb1/2)0.65Ti0.35]O3 single crystal

The temperature dependences of acoustic phonon mode and the central peak have been investigated in Pb[(In1/2Nb1/2)(0.65)Ti-0.35]O-3 single crystal by Brillouin scattering. Longitudinal acoustic phonon begins to show marked softening below the Burns temperature T-B similar to 700 K. The longitudinal acoustic phonon mode exhibits clear anomalies at the cubic-tetragonal phase transition temperature of 540 K and at the tetragonal-rhombohedral one of 460 K. Below 600 K, the relaxation time calculated from the phonon mode agrees well with that of the broad central peak, suggesting a coupling between the local polarization and strain fluctuations of polar nanoregions. This temperature has been identified as another characteristic temperature T* besides T-B, where the formation of long-lived polar nanoregions accompanied by the local strain fields governs the relaxation dynamics. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3058606]