The investigation of equilibrium and nonequilibrium phase transition properties of mixed Ising model

The mixed spin ferrimagnetic Ising system with a random crystal field has been investigated by making use of a method which combines equilibrium theory of critical phenomena and theory of irreversible thermodynamics. Firstly, the magnetic properties of sub-lattice magnetizations and order parameters and equilibrium susceptibilities have been investigated under the mean field approximation. Then, kinetic equations of the system have obtained using the Helmholtz free energy production expression. At this point, relaxation times and dynamic susceptibilities of the mixed spin ferrimagnetic Ising system have been obtained with solutions of the kinetic equations. The temperature dependencies of the dynamic order parameter susceptibilities near the phase transition temperatures have been analyzed for limits of low and high frequencies and according to various values of non-diagonal Onsager phenomenological rate coefficient. Finally, the frequency variances of the dynamic total and staggered susceptibilities near the phase transition points are studied by Argand diagrams as well as isothermal double logarithmic plots of magnetic absoption and dispersion factors.