Theoretical study of dielectric susceptibility in ferroelectric thin films

Based on a pseudospin-phonon interaction model dielectric susceptibility in ferroelectric thin films was studied by using double-time Green's function s method. The dielectric susceptibility peak shifts up to higher temperatur e with increasing the pseudospin-phonon coupling. Critical pseudospin-phono n couplings were obtained. Below the critical coupling Curie temperature fo r the film is lower than that for the bulk and the transition temperature f or the film decreases with decreasing the film thickness: above the critica l coupling Curie temperature for the film is higher than that for the bulk and the transition temperature for the film increases with decreasing the f ilm thickness. (C) 2001 Elsevier Science B.V. All rights reserved.