First order ferroelectric phase transition phenomenon in alkali-phosphate crystal by using Green’s function approach

Abstract

In this paper, first order phase transition phenomenon in CsH2AsO4 crystal has been theoretically investigated. With the help of a simple PLCM modified model presently Hamiltonian, with the consideration of four body interaction SizSjzSkzSlz, cubic, and quartic phonon anharmonic interactions, and another all possible interactions are added into it. The contribution of pseudo spin parameter <Sz> and <Sx> are also introduced here which accounts for the spontaneous polarisation. It is shown that soft mode frequency, and phase transition phenomenon such as, permittivity, loss tangent, and Cochran’s mode frequency in the vicinity of Curie’s temperature at about 145.5K due to anharmonicity within the crystal. Observed the obtained theoretical consequences of above parameters are in well resembles with the experimental results of earlier authors.