Theoretical investigation of structural phase transition and microwave dielectric properties in triglycine sulphate (TGS) crystal

Abstract

By using the extended two sublattice pseudospin coupled mode (PLCM) model by summing third-order and fourth-order anharmonic interactions as well as extra spin lattice interactions, direct spin-spin interaction and electric field terms is considered for triglycine sulphate crystal (TGS) crystal. With the help of double-time thermal dependent Green’s function method and Dyson’s equation, expressions for soft mode frequency dielectric constant and loss tangent for triglycine sulphate crystal. By fitting the model values in the theoretical expressions, thermal variations of soft mode frequency, dielectric constant and loss tangent are calculated and compare well with the experimental data of Bye <em>et al</em>.