Study of ferroelectric phenomena and other related properties in NaKC4H4O6•4H2O crystal

We calculated ferroelectric and electrical permittivity properties of H-bonded-type NaKC4H4O6.4H2O crystal within modified two sublattice pseudospin lattice coupled mode model Hamiltonian extended by the phonon anharmonic interactions terms, indirect spin-lattice coupling and direct spin-spin coupling interaction terms along with external electric field terms. The model Hamiltonian is developed by the modification of the semi-microscopic Mitsui's mode model. With the help of double thermal Green's function method and symmetric decoupling scheme, we obtain the theoretical expressions of shift, width, normal mode frequency, Curie temperatures, dielectric permittivity, tangent loss and spontaneous polarization for NaKC4H4O6.4H2O (RS) crystal. The numerical calculation has been obtained by setting different model parameters in derived expressions. The thermal dependence of the above properties has been calculated and theoretical results are well agreed with the experimental results of Ismailzade et al., Jona and Shirane. A comprehensive investigation of thermal variation on phase transitions of ferroelectric normal mode frequency, electrical permittivity, dielectric loss and spontaneous polarization properties of NaKC4H4O6.4H2O (RS) crystal has been obtained.