Antiferroelectric thin films phase diagrams

Abstract

In this article the size effects of phase transitions and polar properties of the thin antiferroelectric films are considered. We modified the 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. It is 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 PbZrO₃ thin films.

Keywords:

• Antiferroelectrics
• Size effect
• Depolarization field
• Thin films