Evolution of the Critical Behavior in Pure and Deuterated Ferroelectric Crystals of the TGS Family

Abstract

Experimental data of spontaneous polarization in pure and deuterated crystals of the triglycine sulfate (TGS) family have been obtained by means of pyroelectric charge measurements. The critical exponent β, that indicates the temperature dependence of the spontaneous polarization P _S ∝ (T _C −T)^β, decreases with deuteration in triglycine sulfate (TGS) family crystals, specially in the case of deuterated triglycine selenate (DTGSe). Monte Carlo simulations of the equivalent neighbour Ising model are performed to analyse to what extent the experimental behaviour can be explained by a change in the interaction range between dipoles. From the simulations we find a possible way to explain the experimental results based on a short range dominated dipole interaction. However fitting to experimental results is not perfect, so we propose some other possible mechanisms like an increase in the degree of freedom of individual dipoles.