Magnetism of Nanometer-Scale Graphite with Edge or Topological Defects

Abstract

Abstract Magnetic structure is studied for several π-networks of graphite-like structures with edge and/or topological defects using the tight-binding model (the Hückel model). Zigzag-edged graphite have 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 hexagons) in graphite modifies the band structure, some of which have a flat lowest 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.