Tricritical point behavior and quadrupole interactions in ferroelectrics

Abstract

It is shown that the generalization of the effective field expression to take into account in adition to dipolar, quadrupolar, octopolar and higher order multipolar terms, leads to a more general equation of state which describes better the dependence of polarization on temperature and external electric field. The cases of hydrogenated and deuterated members of the TGS family are examined.