Fourth Order Interaction Effects on the Antiferromagnetic Structures. I. fcc Hubbard Model

Abstract

Effects of the fourth order interactions among localized spins are analyzed somewhat in details in the fcc single band Hubbard model near the insulator limit. The longer range Heisenberg type interactions change the stable regions for the spin structures specified by the wave number. The four spin interactions lift the degeneracies of the structures with equivalent wave numbers to make them noncollinear. Discussion on the mixing of the structures with inequivalent wave numbers is given.