Anti-Ferroelectric Thin Films Phase Diagrams

TL;DR

This paper investigates size effects on phase transitions and polar properties of antiferroelectric thin films, providing a theoretical framework that explains experimental observations of hysteresis loop transformations.

Contribution

It introduces a modified phenomenological model with analytical expressions for thickness-dependent coefficients, explaining phase behavior in thin antiferroelectric films.

Findings

Double hysteresis loop transforms into single with decreasing film thickness.

Theoretical results align with experimental data on PbZrO3 thin films.

Derived analytical expressions for free energy coefficients.

Abstract

In the paper we consider size effects of phase transitions and polar properties of the thin antiferroelectric films. We modified phenomenological approach proposed by Kittel. The Euler-Lagrange equations were solved by direct variational method. The free energy with renormalized coefficients depending on the film thickness has been derived. The approximate analytical expression for the coefficients dependence on film thickness, temperature, polarization gradient coefficient and extrapolation lengths were obtained. We have shown how the anti-ferroelectric double hysteresis loop transforms into the ferroelectric single one under the film thickness decrease. Proposed theoretical consideration explains the experimental results obtained in antiferroelectric PbZrO_3 thin films.