A special case of the spin system proposed in the previous paper (i.e., paper I of the same series) is considered, which includes only the Ising term besides the four-spin coupling. In view to describe adequately collinear metamagnets, the thermodynamic properties of this model are investigated....

A two-sublattice spin model is proposed with special four-spin interactions besides the usual exchange terms. The four-spin interaction terms are assumed not to be the even functions of the spin sublattice operators. Thermodynamical properties of this model are investigated in the molecular...