Random mixture of Ising systems of different spin values

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Abstract
The magnetic properties of the Ising mixture of a site model of A and B atoms, of which the magnetic moments, spins, concentrations and exchange energies are mu A, mu B, SA, SB, pA, pB, JAA, JAB and JBB, are investigated. As examples, mixtures with S=1 and S=1/2, the former of which has the anisotropy D, are studied by the distribution function method in the Bethe approximation. The critical temperature (phase boundary between the paramagnetic (P)-ferromagnetic (F) and paramagnetic-antiferromagnetic (AF) phases), the energy and the zero-field susceptibility in the paramagnetic phase are obtained. They are expressed in terms of generalised Brillouin functions as a natural extension of the S=1/2 Ising model and the classical Heisenberg model.