Nonpairwise Magnetic Interactions in Fe and Implications for Short-Range Order above T c

Electronic-structure calculations show that the magnetic interactions between atoms in Fe have strong nonpairwise dependence. The nearest-neighbour coupling, J 1 , dominates and is much weaker for small perturbations around the ferromagnetic state than in the opposite limit of a disordered local moment configuration. This is consistent with substantial short-range order above T c .