Magnetotransport of nanoporous nanographite domain network and its oxygen-adsorption effect Original Research Article

Nanographite has localized spins originating from nonbonding π-electron state (edge state) on their edge sites. Nanoporous activated carbon fibers (ACFs), which consist of a 3D disordered network of nanographite metallic domains, show a large positive magnetoresistance at low temperatures. The magnetoresistance is greatly reduced upon magnetic oxygen adsorption. The large oxygen-adsorption effect on the magnetotransport is theoretically explained in terms of the interaction between the electric dipole moment of the edge-state π-electron and the electric quadrupole moment of an adsorbed oxygen molecule. The theoretical calculation reproduces the experimentally reported strength of the exchange interaction between oxygen molecule spin and the edge-state spin, in addition to the behavior of the magnetoresistance.