A graphene nanoribbon with zigzag edges has a gapped magnetic ground state with an antiferromagnetic interedge superexchange interaction. We present a theory based on asymptotic properties of the Dirac-model ribbon wave function which predicts W-2 and W-1 ribbon-width dependencies for the superexchange interaction strength and the charge gap, respectively. We find that, unlike the case of conve...

In preparing this note, we have examined many textbooks of magnetism where the mechanism of the superexchange interaction is discussed. We realize that it may be difficult for readers (in particular graduate students and undergraduate students studying on the magnetism) to understand the physics on the superexchange interactions from these textbooks, partly because of the limited space of the t...

A new hexagonal bipyramidal Ni8 cluster is reported and its magnetic behaviour is analyzed. The molecular structure consists of a hexagonal wheel capped by two additional apical Ni(2+) ions. This structure supports ferromagnetic superexchange interactions between adjacent Ni(2+) ions in the wheel and an antiferromagnetic superexchange interaction between the wheel and apical Ni(2+) ions.