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Magnetic Moment and Band Structure Analysis of Fe, Co, Ni-modified Graphene-nano- ribbon

Magnetic properties and band characteristics of graphene-nano-ribbon (GNR) modified by Fe, Co, and Ni were analyzed by the first principles DFT calculation. Typical unit cell is [C32H2Fe1], [C32H2Co1] and [C32H2Ni1] respectively. The most stable spin state was Sz=4/2 for Fe-modified GNR, whereas Sz=3/2 for Co-case and Sz=2/2 for Ni-case. Atomic magnetic moment of Fe, Co and Ni were 3.63, 2.49 and 1.26 μB, which were reduced values than that of atomic Hund-rule due to magnetic coupling with graphene network. There is a possibility for a ferromagnetic Fe, Co and Ni spin array through an interaction with carbon pi-conjugated spin system. By expanding a unit cell of Co-modified case as [C96H6Co3], ferromagnetic like spin state and ferrimagnetic like one were compared. It was concluded that ferromagnetic state was more stable magnetic state. Band calculations of Co-modified case show half-metal like structure with relatively large band gap (0.55eV) for up-spin, whereas small gap (0.05eV) for down-spin. This suggested a capability of spintronics application like a spin fiter.