Phenomenological Theory of Antiferroelectric Transition. I. Second-Order Transition

TLDR: In this article, the second-order linear antiferroelectrics were modelled as a function of polar and antipolar variables, each of which is proportional to sum and difference of polarizations of two sublattices respectively, and it contains dimensionless temperature and external field as parameters.

Abstract: Kittel's free energy expression as normalized to involve only dimensionless variables, and manipulated to explain behaviors of second-order linear antiferroelectrics. It is a function of polar and antipolar variables, each of which are proportional to sum and difference of polarizations of two sublattices respectively, and it contains dimensionless temperature and external field as parameters. Free energy maps as functions of the two variables were computed at various values of two parameters. They visualize stability of states and how induced transition occurs under the external field. Stabilities of states were examined analytically, and restrictions on the two parameters for stability were obtained. Below the transition point antiferroelectric state is always more stable than polar state. Under external field, the well-known double hysteresis loop was explained satisfactorily considering stability of the state on two branches of polarization vs. field. Critical field for induced transition was also cal...