Dielectric hysteresis loops of first-order ferroelectric bilayers and antiferroelectrics

Abstract

We consider a ferroelectric bilayer or superlattice with an antiferroelectric interface coupling between two materials which have first-order phase transitions in the bulk. The system is described by a Landau free-energy expression including a bilinear coupling. A detailed discussion is given for the case when the component materials are the same. For equal thicknesses the free energy is the same as for a bulk first-order antiferroelectric. For this, analytical expressions are given for the supercooling, thermodynamic and superheating critical temperatures. Dielectric hysteresis loops are calculated numerically, and it is shown that they can be classified according to a simple scheme. A qualitative discussion is given of the effect of including biquadratic interface coupling. For a general thickness ratio in the bilayer, an analytical result is found for the supercooling temperature and the other two are calculated numerically. Typical dielectric hysteresis loops are shown, and a classification scheme is presented.