UNCONVENTIONAL ELECTRONIC AND MAGNETIC STRUCTURES OF EDGE STATES IN NANOGRAPHENE

The electronic structure of nanographene depends crucially on its edge shape. The periphery of an arbitrary shaped nanographene sheet is described in terms of a combination of zigzag and armchair edges. In zigzag edges, nonbonding π-electron state (edge state) is created in spite of the absence of such state in armchair edges according to theoretical and experimental works [1-3]. Therefore, the zigzag edges are chemically active due to the presence of edge state located at the Fermi level. Furthermore, the localized spins of edge state contribute to make nanographene magnetic. We investigated the magnetic properties of nanographene and nanographite, the latter of which is stacked nanographene sheets, and their guest adsorption effect using nanographene-based nanoporous carbon (activated carbon fibers (ACF)) [4,5]. ACFs consist of a 3D disordered network of nanographite domains, each of which is a stack of 3-4 nanographene sheets with a mean intra-sheet size of ca.2 nm. The magnetism of an individual nanographene sheet is described as ferrimagnetic structure with a net non-zero magnetic moment created by the cooperation of strong ferromagnetic intra-zigzag-edge (J0) and less strong ferromagnetic/antiferromagnetic (J1) inter-zigzag-edge interactions acting between the edge-state spins. Then an individual nanographite domain, in which the edge-state spins o