Effect of band structure on ferromagnetism*

We extend Nagaoka's study of the ferromagnetism of nearly half-filled bands in the infinite-repulsion limit of the Hubbard model by including next-nearest-neighbor tight-binding overlap matrix elements K2. Particles can now get past one another, even in one dimension. We find corroboration of Nagaoka's results, viz., either possibility or impossibility of ferromagnetism depending on the relative sign and magnitude of K2.