Origin of Raman Scattering and Ferroelectricity in Oxidic Perovskites

Abstract

The second-order Raman scattering and the temperature dependence of the ferroelectric soft mode in $\mathrm{AB}{\mathrm{O}}_{3}$ perovskites are explained quantitatively in terms of a nonlinear shell model by assuming an anisotropy in the oxygen polarizability. This model yields a new explanation for the origin of ferroelectricity in perovskites.