Coexistence of the Critical Slowing Down and Glassy Freezing in Relaxor Ferroelectrics

TL;DR

This paper presents a dynamical model for relaxor ferroelectrics that captures the coexistence of critical slowing down and glassy freezing, aligning well with experimental observations in PMN.

Contribution

It introduces a model explicitly accounting for both phenomena in relaxor ferroelectrics and validates it against experimental data.

Findings

Small local freezing degree at high temperatures

Critical slowing down significantly influences system dynamics

Predicted relationship between permittivities matches experiments

Abstract

We have developed a dynamical model for the dielectric response in relaxor ferroelectrics which explicitly takes into account the coexistence of the critical slowing down and glassy freezing. The application of the model to the experiment in PMN allowed for the reconstruction of the nonequilibrium spin glass state order parameter and its comparison with the results of recent NMR experiment (Blinc et al., Phys. Rev. Lett. 83, No. 2 (1999)). It is shown that the degree of the local freezing is rather small even at temperatures where the field-cooled permittivity exceeds the frequency dependent permittivity by an order of magnitude. This observation indicates the significant role of the critical slowing down (accompanying the glass freezing) in the system dynamics. Also the theory predicts an important interrelationship between the frequency dependent permittivity and the zero-field-cooled permittivity, which proved to be consistent with the experiment in PMN (A. Levstik et. al., Phys. Rev. B 57, 11204 (1998)).