Theoretical prediction of synthesis methods to create magnetic nanographite

We propose that to modify zigzag edges of nanographite structures by hydrogenation, fluorination or oxidation is a method to create magnetic materials made only from light elements. These reactions and methylene addition are compared with each other in several aspects by considering a graphene ribbon having mono-hydrogenated zigzag edges as a starting material. A local-spin-density approximation was applied to the electronic band-structure calculation of nanographite ribbon structures and stability of each ribbon was tested by the first-principles manner. Among possible reactions for graphene ribbon, hydrogenation produces the largest magnetic moment per a carbon atom. Since the hydrogenation is exothermic, however, fluorination has advantage, where the reaction is endothermic. The possible maximum moment is 1/3 of that for the ideal hydrogenationed graphene ribbon. A graphene ribbon with an oxidized zigzag edge and a monohydrogenated zigzag edge possesses a partially spin-polarized flat band similar to the fluorinated ribbon. A magnetic moment appears at the monohydrogenated zigzag edge but not at the oxidized edge. No evidence of spin polarization, however, has been found for a methylene-substituted graphene ribbon.