The statistical mechanics of spin-1 Ising model with AFM/AFM interactions on a bilayer Bethe lattice

The spin-1 Ising model is studied for the case of antiferromagnetic (AFM)/AFM interactions on the bilayer Bethe lattice by using the pairwise approach for several values of the coordination numbers q = 3, 4 and 6 when the layers are linked with the external magnetic fields. The ground state (GS) phase diagrams, thermal variations of the order-parameters and the response functions are studied in detail to obtain the phase diagrams of the model. It was found that the system gives only one Neel temperature, T(N), for q = 3. Two T(N)'s and first-order phase transition temperature, T(t), thus tricritical point, are found and the existence of two T(N)'s leads to the reentrant behavior when q = 4 and 6 for some given system parameters. (C) 2009 ElsevierB.V. All rights reserved.