Random Electric Field Instabilities of Relaxor Ferroelectrics

TL;DR

This paper investigates how quenched random electric fields caused by compositional disorder affect phase transitions in relaxor ferroelectrics, revealing that even weak disorder prevents long-range order and leads to a unique correlated polarization state.

Contribution

It introduces a microscopic model and statistical mechanical analysis showing that weak compositional disorder inhibits long-range ferroelectric order in relaxors.

Findings

Weak disorder prevents long-range ferroelectric order.

A random field state with anisotropic, power-law polarization correlations emerges.

Model reproduces key experimental observations in PbMg$_{1/3}$Nb$_{2/3}$O$_3$-PbTiO$_3$.

Abstract

Relaxor ferroelectrics are complex oxide materials which are rather unique to study the effects of compositional disorder on phase transitions. Here, we study the effects of quenched cubic random electric fields on the lattice instabilities that lead to a ferroelectric transition and show that, within a microscopic model and a statistical mechanical solution, even weak compositional disorder can prohibit the development of long-range order and that a random field state with anisotropic and power-law correlations of polarization emerges from the combined effect of their characteristic dipole forces and their inherent charge disorder. We compare and reproduce several key experimental observations in the well- studied relaxor PbMg$_{1/3}$Nb$_{2/3}$O$_3$-PbTiO$_3$.