Lattice Dynamics and Spontaneous Polarization Calculation of Disorder Solid Solution Thin Ferroelectric Films

Abstract

In the framework of nonempirical model of polarizable ions, lattice dynamics and polarization for solid solution thin ferroelectric films PbB′_1/2B^″ _1/2O₃ (B′ = Sc, Ga, In, Lu; B^″ = Nb, Ta) were calculated. The thickness of films was varied from 3 to 41 layers and PbO <B>O₂ terminations of film were considered. It was found, those unstable polar modes are existing in spectra of all compounds for every thickness and eigenvectors of this mode has different character for different terminations. The frequency of “soft” polar mode tends to its corresponding value in bulk crystal with increasing of film thickness. In phase, distorted by eigenvector of this mode, the film thickness dependence of spontaneous polarization was calculated. Also it was found that layer-by-layer polarization profile for films with different terminations are differing.

Acknowledgment

This work is supported by the Russian Foundation of Basic Research (No 06-02-16091) and by Grant of President of RF “Leading Science School” (NS-1011.2008.2)