Temperature dependence of ferroelectric mode frequency, dielectric constant and loss tangent in CsH2PO4 and deuterated CsH2PO4 crystals

The pseudo-spin lattice coupled mode model by adding third- and fourth-order phonon anharmonic interactions and extra spin-lattice interaction term has been considered for CsH2PO4 (abbreviated CDP) and deuterated CsH2PO4 (abbreviated DCDP) crystals. Expressions for shift and width of response function, vibrational normal mode frequency, dielectric constant and loss tangent have been evaluated. Double time temperature dependent Green’s function method has been used for derivation. Fitting the values of model parameters in expressions, the temperature dependence of soft mode frequency, dielectric constant and loss tangent have been calculated. Theoretical results are in agreement with experimental results reported by Blinc et al16