The observation of glassy polarization behavior in crystalline ferroelectric materials

We summarize some of our recent measurements of the temperature dependence of the optic index of refraction, n(T), in several different classes of ferroelectrics. The common thread between these different materials is that in all of them the translational symmetry is strongly broken. Far above the usual ferroelectric transition temperature Tc up to a temperature Td, we show that the crystals possess a local, randomly oriented, nonreversible polarization. Using a simple model for this behavior, we can account for it qualitatively and in some systems quantitively understand Td. We believe this model contains the basic physical understanding of ferroelectrics that have a diffusive phase transition.