The electronic structure of graphene is described in terms of massless Dirac fermion moving on the two-dimensional (2D) honeycomb bipartite lattice. When a graphene sheet is cut into nanofragment (nanographene) having open edges, the electronic structure is strongly modified depending on the geometry of the edges created; zigzag edge and armchair edge. In the zigzag edge, nonbonding edge state of π-electron origin is created as a consequence of broken symmetry in the pseudo-spin of the Dirac fermion, in spite of the absence of such state in the armchair edge. The edge state which has a large local density of states in the zigzag edge region is strongly spin polarized, and the presence of localized spins of edge states makes nanographene magnetic. Here the strong ferromagnetic interaction between the edge-state spins in a zigzag edge is responsible for carbon-based ferromagnetism. We present the magnetic properties of nanographene with the employment of nanographene-based activated carbon fibers. The magnetic and electronic properties are investigated using experiments of magnetic susceptibility, ESR and near edge X-ray absorption fine structure.
展开▼
