Temperature dependence of soft mode frequency, dielectric constant and loss tangent in PbHPO₄ crystal in presence of electric field

Abstract

An extended two sublattice pseudospin lattice coupled mode model by adding third and fourth-order phonon anharmonic interactions terms as well as external electric field term has been considered for lead hydrogen phosphate crystal and its isomorphs. With the help of double-time temperature dependent Green’s function method, theoretically, expressions for shift, width, soft mode frequency, dielectric constant and loss tangent are derived. By fitting model values in the theoretical expressions, temperature and electric field dependence of soft mode frequency, dielectric constant and loss tangent is calculated for PbHPO₄ crystal in presence of electric field. The theoretical results compared with experimental results of Smutny and Fousek [<i style="">Ferroelectrics</i>, 21 (1978) 385] show good agreements.