PHYSICA SCRIPTA, cilt.47, sa.3, ss.328-332, 1993 (SCI-Expanded)
A spin-1 Ising model with bilinear (J) and biquadratic (K) exchange interactions in the presence of an external magnetic field is studied using the lowest approximation of the cluster variation method. Beside the stable solutions, metastable and unstable solutions of the system are also found. All these solutions are shown in the two dimensional phase space. The influence of an external magnetic field and the ratio of the coupling parameter alpha = J/K on metastable and unstable solutions are investigated.