FLUCTUATIONS IN FERROELECTRICS AND DIELECTRIC-PROPERTIES FROM THE FOKKER-PLANCK EQUATION

The Fokker-Planck equation is used to study the dielectric susceptibil ity dispersion in ferroelectrics within the Landau-Ginzburg model. Sub sequent consideration of fluctuations, recently used for calculations in the paraelectric phase, is extended. The results of a more comprehe nsive study including calculations for both the ferroelectric phase an d refined calculations for the ferroelectric phase are presented here. The obtained results allow to explain qualitatively the resonance dis persion close to the critical point, observed in SbSI-type ferroelectr ic crystals. Besides, the diffuse phase transition in relaxer ferroele ctrics and its spontaneous transfer to the first-order phase transitio n is explained within the considered model.