Critical behaviour in ferroelectrics as studied by nonlinear dielectric effect. Invariants of the electric susceptibility in a biasing field

摘要

The simplest equation of state compatible with the Widom and Griffiths scaling hypothesis have been built for the uniaxial ferroelectrics TGS and MAPCB. The explicit forms have been found of the scaling invariants deduced from the curves of the electric susceptibility measured in a constant biasing field. Smooth and sharp inflection points of the susceptibility curve in the vicinity of the critical temperature have been classified. The invariants and the inflection points have been used to determine critical parameters of TGS and MAPCB.