Size effects in the thin films of order - disorder ferroelectrics subject to the depolarization field

TL;DR

This paper investigates size effects in thin films of order-disorder ferroelectrics considering depolarization fields, revealing how film thickness influences phase transition and polarization behavior.

Contribution

It introduces a mean field model accounting for depolarization fields to describe size effects in order-disorder ferroelectric films, including critical size and temperature calculations.

Findings

Critical size and temperature depend on film thickness and depolarization field.

All dipoles order at T=0 for h>hc, regardless of thickness.

Displacement-type ferroelectrics have larger critical thickness and sharper polarization profiles.

Abstract

The films of order-disorder type ferroelectrics were considered in the mean field approximation taking into account depolarization field. It was shown that size effects in this system could be described on the base of bulk system equation of state with Curie temperature dependent on the film thickness. The critical size hc and critical temperature Tc of phase transition from ferroelectric to paraelectric phase was calculated allowing for the depolarization field contribution. The comparison of the polarization dependence on the film thickness, temperature and electric field for the films of order-disorder and displacement type ferroelectrics is performed. In particular it was shown that all the dipoles become ordered at T=0 independently on the film thickness for h>hc contrary to the displacement type ferroelectrics. Critical thickness appeared larger and polarization distribution sharper for the displacement type ferroelectrics than for order-disorder type ferroelectrics.