Magnetization profile for impurities in graphene nanoribbons

Physical review. B, Condensed matter (Impact Factor: 3.66). 08/2011; 84. DOI: 10.1103/PhysRevB.84.195431
Source: arXiv

ABSTRACT 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.

  • [Show abstract] [Hide abstract]
    ABSTRACT: A form of an indirect Ruderman-Kittel-Kasuya-Yosida (RKKY)-like coupling between magnetic on-site impurities in armchair graphene nanoribbons is studied theoretically. The calculations are based on a tight-binding model for a finite nanoribbon system with periodic boundary conditions. A pronounced Friedel-oscillation-like dependence of the coupling magnitude on the impurity position within the nanoribbon resulting from quantum size effects is found and investigated. In particular, the distance dependence of coupling is analysed. For semiconducting nanoribbons, this dependence is exponential-like, resembling the Bloembergen-Rowland interaction. In particular, for metallic nanoribbons, interesting behaviour is found for finite length systems, in which zero-energy states make an important contribution to the interaction. In such situation, the coupling decay with the distance can be then substantially slower.
  • Source
    [Show abstract] [Hide abstract]
    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.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The stability and electronic properties of the Fe atoms embedded in divacancy defects in graphene nanoribbons (GNR) with zigzag-shaped edges have been studied by first-principles calculations. When Fe is positioned in the middle of the ribbon, it has little effect on the edge C atoms, which reserves the flat edges of graphene nanoribbons. On the other hand, when Fe atom is near the edge, structural distortion takes place resulting in tilted-edge structure with low energies. This indicates that the Fe atoms prefer to occupy divacancy sites near the edges. This is also in consistent with the analyses of electronic structures. Meanwhile, our results reveal that embedding Fe atom in the graphene nanoribbons is an effective method to make the GNR possessing metallic properties.
    Physica B Condensed Matter 05/2014; 441:28–32. · 1.28 Impact Factor

Full-text (2 Sources)

Available from
Jun 5, 2014