Phase Transitions and Fundamental Ferroelectric Dispersion in DMAAl$\text{}_{1-x}$$Cr_{x}S$ Crystals

This paper presents the results of investigations of the temperature dependence of heat capacity and dielectric dispersion in the vicinity of ferroelectric-ferroelastic phase transition of dimethylammonium metal sulphate hexahydrate crystals DMAAl$\text{}_{1-x}$$Cr_{x}S$. In particular, it is shown that the isomorphous substitution of metal ion noticeably changes the temperature of phase transition and parameters of the fundamental ferroelectric dispersion observed around $T_{c1}$. These changes are explained in terms of clusters sizes and dynamics in the framework of order-disorder type phase transition mechanism.