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 DELTA-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.