Random Field Distribution Function in the Relaxor Ferroelectric Thin Films

Abstract

The calculation of random field distribution function in the relaxor ferroelectrics was performed in the statistical physics framework. The point charges and electric dipoles randomly distributed in Burns reference phase were considered as the main sources of random electric field. The influence of the surfaces was calculated in the model of image charges and dipoles distributed in all the space. The contribution of these real and image sources of random field was taken into account. The characteristic features of calculated random field distribution function namely its half-width and the most probable electric field value were shown to be dependent both on the field sources parameters and on the dielectric permittivity of the surrounding media and ferroelectric material. It was shown that in general case the degree of disorder in the film of a relaxor could be either larger or smaller than in the bulk. Because of this the change of phase diagram with transformation of dipole glass state into ferroglass and vice versa can be expected. The developed theory opens the way of calculation of the disordered ferroelectrics film properties by averaging of the properties, calculated in host phase (Burns reference phase for the relaxors) as functions of electric field.