Temperature Dependence of Dielectric Constant and Loss Tangent in Methyl Ammonium Aluminium Alum

Abstract

The ferroelectric phase transition of MASD alum was studied by model of pseudospinlattice coupled mode which has been modified by including cubic and quartic phonon anharmonic interaction terms. With the help of double-time temperature dependent Green's function method and modified Hamiltonian, expressions for dielectric constant, soft mode frequency and loss tangent has been evaluated. By fitting model values of physical quantities in the theoretical expressions, temperature dependence of dielectrc, soft mode frequency and loss tangent have been obtained and compared with literature values which shows a good agreement.