Superexchange Interaction

Abstract

In linear MXM system, where M is transition metal and X is bridge-anion, the magnetic interaction is often antiferromagnetic. In Kanamori-Goodenough rule, the magnetic interaction can be predicted based on slight charge transfer from ligand anion to transition metal. As the magnetic interaction occurs between transition metal atoms via ligand anion, it is called “superexchange interaction”. In this chapter, superexchange interaction is reconsidered, from the viewpoint of molecular orbital theory. In fact, there are two direct interactions between transition metal and ligand anion. One is charge transfer, and the other is orbital overlap. Kanamori-Goodenough rule is revised (“superexchange rule”). In MnFMn, Mn₄F₄ and KMn₈F₁₂ models, the mechanism of superexchange interaction is explained according to superexchange rule. In Cu₂F₂ model, slight σ-type superexchange interaction occurs in bent CuFCu. Finally, two-atom bridge superexchange interaction is explained in MnCNMn model.