Fourth Order Interaction Effects on the Antiferromagnetic Structures. II. A Phenomenological Model for NiS2

Possible fourth order interactions among localized spins in an orbital-degenerate case ( S >1/2) are discussed as an expansion from the Mott insulator limit, with reference to a model for the electronic structure of NiS 2 . Then a phenomenological model to study the antiferromagnetic structure of NiS 2 is presented.