Explanation of Onset Ferroelectric Transition and Anomalous Tangent Delta in HBonded Rubidium Dihydrogen Phosphate Crystal

Abstract

The H-bonded ferroelectric and ordered-disordered, type of Rubidium Dihydrogen Phosphate crystal is theoretically investigated. It undergoes a ferroelectric phase transition at 146K. Modified earlier author’s (Ganguli et al, 1980) simple Pseudo Spin Lattice Coupled mode (PLCM) model Hamiltonian by adding some extra interactions term into it, like third-order and fourth-order, phonon anharmonic interactions, direct spin-spin terms, extra spin-lattice terms and four spin coupling terms are added. By using Zuberav’s statistical approach, two times temperature dependent Green function method, and Dyson’s equation in the mean-field approximation (MFA), to obtain the formulae of various quantities like (ε), Ω̃, and tan(δ), Curie’s temperature, and response function (shift and width) as a function of temperature. Thermal variations of above quantities are obtained for Rubidium Dihydrogen Phosphate (RbH2PO4) crystal. A comparison with theoretical findings has been made with the experimental findings reported by (Peercy et al, 1974) which shows good agreement.