Disorder and relaxation mode in the lattice dynamics of PbMg$_{1/3}$Nb$_{2/3}$O$_3$ relaxor ferroelectric

TL;DR

This study investigates the lattice dynamics of PbMg$_{1/3}$Nb$_{2/3}$O$_3$ relaxor ferroelectric using inelastic neutron scattering, revealing a relaxation mode linked to order-disorder behavior affecting diffuse phase transitions.

Contribution

It provides new insights into the relaxation modes and order-disorder dynamics in relaxor ferroelectrics through neutron scattering analysis.

Findings

Observation of coexistence of central peak and quasielastic scattering.

Quasielastic linewidth follows a temperature-dependent $ ext{Gamma}_0 + Dq^2$ law.

Relaxation time obeys Arrhenius law, indicating thermally activated dynamics.

Abstract

The low-energy part of vibration spectrum in PbMg$_{1/3}$Nb$_{2/3}$O$_3$ 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 quasi-elastic scattering in PMN indicates that order-disorder behaviour plays an important r\^ole in the dynamics of diffuse phase transitions.