| Graphene, a single layer of carbon atoms arranged in a honeycomb-like lattice structure, is a unique 2-dimensional non-magnetic semiconductor with zero gap. Graphene has excellent electronic, thermal and mechanical properties, therefore it has wide applications for the high-performance nano-electronic devices, composite materials, field emission materials, gas sensors and energy sources etc.In this paper, we have investigated the electronic structures and magnetism for the Fe monolayer/graphene hybrid structure by using the full-potential lin-earized augmented plane wave (FLAPW) method combining with the generalized gradient approximation (GGA). We considered three kind of structures for the Fe monolayer/graphene hybrid structure, i.e., the Fe monolayer adsorbed on graphene surface (Fe/G), Fe monolayer was sandwiched between the two graphene layers (G/Fe/G), graphene was sandwiched between the two Fe monolayer (Fe/G/Fe). We have obtained the optimized lattice constants between the Fe monolayer and graphene through the variations of total energy with the distance between Fe mono-layer and graphene. The calculated optimized lattice constants of Fe/G, G/Fe/G arid Fe/G/Fe structures are 1.662 A,1.889 A and 2.408 A, respectively, and the magnetic moments of Fe atoms are 2.555μB,2.605μB and 3.106μB, while the carbon atoms of graphene have induced magnetic moments of -0.039μB,-0.005μB and 0.007μB, respectively. Among the three structures, the magnetic moments of Fe atoms come mainly from the 3d electrons, while the contributions of s, p electrons are small. Magnetic moments of carbon atoms come mainly from the 2p electrons, There is hybridization of sp-d orbitals between the C and Fe atoms. As shown in the energy band diagram, one can see that in the energy band of spin up states, the location of Driac point, positioned on K point at Graghene, not changed in the Fe/G structures; while it locates in the Fermi level above in the energy band of spin down states. And in the energy band of spin up states, the location of Fermi level on K point in the G/Fe/G structures has the same characteristic as Driac point at Graghene; while it moves toward above the Fermi level in the energy band of spin down states. In the energy band of spin up states, the location of Driac point, positioned on K point at Graghene, locates in the Fermi level below in the Fe/G/Fe structures; while it locates in the Fermi level location in the energy band of spin down states. It can be seen from the charge density figure that strong covalent bond is created between C atoms of graphene, it also can be found from the charge density that there is significant charge focus phenomenon between C and Fe atoms, which implies strong interactions between C and Fe atoms. |
