Correlation between Transition Entropy and the Rhodes-Wohlfarth Ratio in Ferroelectric Materials

A systematic correlation is discovered for a number of ferroelectrics between transition entropy Δ S and the Rhodes-Wohlfarth ratio p c / p s , where p c is the effective dipole moment determined from the Curie-Weiss constant assuming the existence of permanent dipoles, while p s is the saturation moment. The unified theoretical model of ferroelectrics, which is capable of describing essential features of both displacive-type and order-disorder-type ferroelectrics, is shown to reproduce the above correlation strikingly well.