Contribution to the Theory of Paraelectric Relaxation near the Curie Point
Progress of theoretical physics
305 Anomalous critical behavior associated with the order-disorder type ferroelectric transition is investigated. By introducing the concept of effective correlation length, the theory of Glarum and Cole for the dielectric relaxation is extended to the critical region. It is noted that the radius of the semi-microscopic sphere, introduced in their theory, has to be greater than the effective correlation length and hence is strongly temperature dependent near the Curie point. The relaxation of
... The relaxation of the polarization of the semi-microscopic sphere shows two characteristic features, the critical slowing-down and the nonlinearity. lt is this nonlinear effect which in the present theory accounts for the anomalous polydispersive behavior of the dielectric relaxation near the Curie point. For an actual calculation, a simple model is introduced in which the size of the semi-microscopic sphere is taken to be equal to the effective correlation length and in which the smaller scale local fluctuations are treated as rapid random fluctuations. Using this model, the dynamic susceptibility is calculated and is shown to exhibit a behavior which is in some respects similar to that observed in experiment.