Magnetism of nanometer-scale graphite with edge or topological defects

Magnetic structure is studied for several pi-networks of graphite-like structures with edge and/or topological defects using the tight-binding model (the Huckel model). Zigzag-edged graphite bare edge states, which form a partly flat band at the Fermi energy. Short range repulsion (the Hubbard U) is enough to induce huge magnetic moments coming from spin polarization of localized electrons on the edge. While, introduction of azupyrene defect (two pentagons and two heptagons instead of four hesagons) in graphite modifies the band structure, some of which have a flat lon-est excitation band. We propose a series of one-dimensional polymers with a flat band, which is exactly shown to be ferromagnetic for electron doping up to the half-filling of this band, so long as the system is well described by the Hubbard model.