STABLE, METASTABLE AND UNSTABLE SOLUTIONS OF A SPIN-1 ISING SYSTEM INTHE PRESENCE OF MAGNETIC-FIELDS DUE TO THE DIPOLE AND QUADRUPOLE-MOMENTS

The spm-1 Ising model with bilinear (J) and biquadratic (K) interactio ns is studied for magnetic fields H-S and H-Q representing dipole and quadrupole moments, respectively, by using the lowest approximation of the cluster variation method. The influence of H-S, H-Q, and alpha = J/K on metastable and unstable solutions, which are very important for many theoretical and experimental works, is investigated and it is fo und that metastable and unstable solutions occur at high temperatures when alpha and H-Q increased. However if H-S is increased, metastable and unstable solutions can be found only at low temperatures.