Theoretical study of temperature dependence of ferroelectric mode frequency, dielectric constant and loss tangent properties in hydrogen-bonded triglycine sulphate crystal (TGS)

Abstract

Two-sublattice pseudospin lattice coupled mode model [Chaudhuri et.al] with addition of third and fourth order phonon anharmonic interactions terms, external electric field term, direct spin-spin interaction term and extra spin-lattice interactions terms has been considered for investigation of phase transition and dielectric properties of classic TGS crystal. With the help of double-time thermal Green’s Function method [Zubarev] the formulae for ferroelectric mode frequency, shift and width functions as well as dielectric constant have been derived for TGS crystal. In this work symmetric decoupling approximation and other terms have been used in contrast to earlier other authors. Therefore, our results are quite different from others’ results. By fitting model values of various parameters in the expressions, temperature dependences of ferroelectric mode frequency, dielectric constant and loss tangent have been obtained for TGS crystal. Present theoretical results agree with experimental results of Aravazhi et al. We observed that two-sublattice pseudospin lattice coupled model along with other terms using symmetric decoupling scheme explains well ferroelectric and dielectric properties of TGS crystal. Present formulae may also explain properties of similar other crystals.