Magnetization profile for impurities in graphene nanoribbons

Physical Review B (Impact Factor: 3.74). 08/2011; 84. DOI: 10.1103/PhysRevB.84.195431
Source: arXiv


The magnetic properties of graphene-related materials and in particular the
spin-polarised edge states predicted for pristine graphene nanoribbons (GNRs)
with certain edge geometries have received much attention recently due to a
range of possible technological applications. However, the magnetic properties
of pristine GNRs are not predicted to be particularly robust in the presence of
edge disorder. In this work, we examine the magnetic properties of GNRs doped
with transition-metal atoms using a combination of mean-field Hubbard and
Density Functional Theory techniques. The effect of impurity location on the
magnetic moment of such dopants in GNRs is investigated for the two principal
GNR edge geometries - armchair and zigzag. Moment profiles are calculated
across the width of the ribbon for both substitutional and adsorbed impurities
and regular features are observed for zigzag-edged GNRs in particular. Unlike
the case of edge-state induced magnetisation, the moments of magnetic
impurities embedded in GNRs are found to be particularly stable in the presence
of edge disorder. Our results suggest that the magnetic properties of
transition-metal doped GNRs are far more robust than those with moments arising
intrinsically due to edge geometry.

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Available from: Mauro S. Ferreira, Oct 05, 2015
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    • "4e6 for the most stable systems. In a recent investigation on the adsorption of a Mn atom on zigzag GNRs [34] it was found that the magnetic moment of the adatom first decreased monotonically as it moved from the CHS to the LHS, but at the EBS the magnetic moment increased. This was explained as a consequence of the fact that the latter impurity configuration had a less dramatic effect on the magnetic moments of nearby edge sites than the LHS. "
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    ABSTRACT: a b s t r a c t We performed ab initio density-functional calculations to investigate the structural, elec-tronic and magnetic properties of nanostructures comprising single-adatoms of Sc, Ti or V adsorbed on a hydrogen-passivated zigzag graphene nanoribbon (GNR). We also investi-gated the affinity of the resulting doped nanostructures for molecular hydrogen. In all cases, the most stable structures featured the adatom at positions near one of the edges of the GNR. However, whereas in the most stable structures of the systems Sc/GNR and V/GNR the adatom was located above a bay of the zigzag edge, Ti/GNR was found to be most stable when the adatom was at a first-row hole site. Adsorption at sites near one of the ribbon edges reduced drastically the average magnetic moment of the carbon atoms at that edge. On the other hand, the magnetic moments of the adatoms on the GNR, as the electronic character of the doped nanostructures, depended on the adsorption site and on the adatom species, but their absolute values were in all cases, except when Sc was at an edge bay site, greater than those of the corresponding free atoms. Our results showed that, of the three systems investigated in this paper, Ti/GNR (except when Ti is adsorbed at an edge bay site) and V/GNR appear to satisfy the criterion specified by the U. S. Department of Energy for efficient H 2 storage, as far as binding energy is concerned. We discussed in detail the differences be-tween the adsorption of H 2 on the system Ti/GNR and the adsorption of H 2 on Ti-adsorbed carbon nanotubes, which have been proposed as a high-capacity hydrogen storage media.
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    ABSTRACT: The spin-polarized transport properties of nonmagnetic (metallic Al and nonmetallic C) atomic chains adsorbed on zigzag graphene nanoribbons (ZGNRs) are investigated by the density functional theory (DFT) combined with the nonequilibrium Green’s function method. We find that the spin polarization of ZGNRs is sensitive to the adsorption sites and atomic types of the chains. As an Al chain is adsorbed on the middle of ZGNR, no spin-polarized transport arises. As the Al chain is adsorbed on the edge of ZGNR, high spin polarization is produced around the Fermi level. The different transport behaviors are originated from the fact that the edge adsorption of Al chain breaks the magnetization symmetry of two edges while the middle adsorption of Al chain only modifies the magnetizations of two edges equally. More prominent spin polarization is generated as a C chain is adsorbed on the edge of ZGNR. The complete spin polarization emerges not only around the Fermi level but also far from the Fermi level, owing to the edge states and the localized states. These results indicate that one can effectively modulate the spin-polarized transports of ZGNRs through adsorbing different nonmagnetic atomic chains.
    Physics of Condensed Matter 02/2013; 86(2). DOI:10.1140/epjb/e2012-30912-5 · 1.35 Impact Factor
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    ABSTRACT: We propose a class of graphene nanoribbons showing strong intrinsic ferromagnetic behavior due to their asymmetry. Such ribbons are based on a zig-zag edged backbone surmounted by a periodic, triangular notched region of variable size. The electronic properties as a function of the topology are investigated. Interestingly, substitutional doping by boron or nitrogen induces half-metallicity. The most effective doping sites can be inferred from the band structure. Given the present rapid development of bottom-up strategies for the synthesis of atomically precise carbon nanostructures the proposed class of nanoribbons emerges as a real candidate for spintronic applications at ambient temperature.
    Physical review. B, Condensed matter 01/2012; 85(24). DOI:10.1103/PhysRevB.85.245405 · 3.66 Impact Factor
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