Phonon Contributions to the Anomalous Specific Heat of Triglycine Sulfate near Tc

Abstract
The ferroelectrics of the triglycine sulfate (TGS) family demonstrate an anomalous contribution to the specific heat near Tc whose peak height can not be accounted for in the usual mean field approximation. It is shown for TGS that this anomaly is due to temperature dependent frequencies of optical phonons near the phase transition temperature.