Relaxor behavior and morphotropic phase boundary in a simple model

TL;DR

This paper introduces a simple model combining long-range dipole interactions and compositional disorder to explain the enhanced dielectric response near the morphotropic phase boundary, highlighting the role of local polarization rotation.

Contribution

The study presents a novel model that captures the dielectric enhancement near MPB through phase competition and local polarization dynamics, validated by Monte Carlo simulations.

Findings

Ferroelectric boundary phase appears at optimal disorder levels.

Large, flexible ferroelectric domains form in the boundary phase.

Huge dielectric response results from local polarization rotation.

Abstract

A simple model to reproduce strong enhancement of dielectric response near the morphotropic phase boundary (MPB) is proposed. This model consists of long-range dipole-dipole interaction and compositional chemical disorder incorporated by the variation in lengths of dipole moments. By applying Monte Carlo simulation, we show that there appears a ferroelectric boundary phase between two types of antiferroelectric phases at an optimal strength of randomness. In the boundary phase, ferroelectric domain becomes remarkably large and flexible to external electric fields, leading to huge dielectric response. This observation indicates that huge dielectric response near the MPB originates from {\it local} polarization rotation under suppressed anisotropy by phase competition.