Disorder and relaxation mode in the lattice dynamics of the PbMg1/3Nb2/3O3 relaxor ferroelectric -: art. no. 092105

The low-energy part of vibration spectrum in PbMg1/3Nb2/3O3 (PMN) relaxor ferroelectric was studied by inelastic neutron scattering. We observed the coexistence of a resolution-limited central peak with strong quasielastic scattering. The line width of the quasielastic component follows a Gamma(0)+Dq(2) dependence. We find that Gamma(0) is temperature dependent. The relaxation time follows the Arrhenius law well. The presence of a relaxation mode associated with quasielastic scattering in PMN indicates that order-disorder behavior plays an important role in the dynamics of diffuse phase transitions.