The edge state of nanographene and the magnetism of the edge-state spins

Enoki, Toshiaki; Takai, Kazuyuki

doi:10.1016/j.ssc.2009.02.054

Cited by 126 publications

(96 citation statements)

References 56 publications

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“…This is analogous with the distinction between Kekule and nonKekule polycyclic hydrocarbon molecules. 17 These theoretical predictions have been confirmed experimentally via scanning tunneling microscopy and scanning tunneling spectroscopy.…”

Section: Introductionmentioning

confidence: 69%

“…1,2 In particular, the unconventional magnetism in graphene based nanostructures is interesting, which may be utilized for spintronics applications. [3][4][5][6][7] Such graphene nanostructures have been fabricated experimentally, [8][9][10][11][12][13][14][15] and interestingly magnetism has been reported in nanographene, 16,17 disordered graphite, 18,19 and grain boundaries in highly oriented pyrolytic graphite. 20 The electronic structure of graphene nanostructure is different from the infinite graphene due to the edge effect.…”

Section: Introductionmentioning

confidence: 99%

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Manipulation of edge magnetism in hexagonal graphene nanoflakes

Kabir

Saha‐Dasgupta

2014

Phys. Rev. B

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We explore possible ways to manipulate the intrinsic edge magnetism in hexagonal graphene nanoflake with zigzag edges, using density functional theory supplemented with on-site Coulomb interaction. The effect of carrier doping, chemical modification at the edge, and finite temperature on the edge magnetism has been studied. The magnetic phase diagram with varied carrier doping, and on-site Coulomb interaction is found to be complex. In addition to the intrinsic antiferromagnetic solution, as predicted for charge neutral hexagonal nanoflake, fully polarized ferromagnetic, and mixed phase solutions are obtained depending on the doped carrier concentration, and on-site Coulomb interaction. The complexity arises due to the competing nature of local Coulomb interaction and carrier doping, favoring antiferromagnetic and ferromagnetic coupling, respectively. Chemical modification of the edge atoms by hydrogen leads to partial quenching of local moments, giving rise to a richer phase diagram consisting of antiferromagnetic, ferromagnetic, mixed, and nonmagnetic phases. We further report the influence of temperature on the long-range magnetic ordering at the edge using ab initio molecular dynamics. In agreement with the recent experimental observations, we find that temperature can also alter the magnetic state of neutral nanoflake, which is otherwise antiferromagnetic at zero temperature. These findings will have important implications in controlling magnetism in graphene based low dimensional structures for technological purpose, and in understanding varied experimental reports.

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Section: Introductionmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Manipulation of edge magnetism in hexagonal graphene nanoflakes

Kabir

Saha‐Dasgupta

2014

Phys. Rev. B

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“…Sharper peaks appear in all samples, with linewidth close to that for sigma dangling bond spins observed in nanoporous carbon materials (B0.1 mT) 41 . On the other hand, the broader peak, which is only observed in ba-GO, has a linewidth similar to that of localized spins originating from the edge of nanographene (B1 mT) 42,43 . The p-electron radical at the edges of graphene is delocalized along the edges to some extent, and exhibits fast spin-lattice relaxation through interaction with the adjacent p-electron system, giving rise to a broad linewidth in ESR.…”

Section: Figure 3 | Characterization Of Go and Ba-go Powder (A) Thermentioning

confidence: 89%

Probing the catalytic activity of porous graphene oxide and the origin of this behaviour

et al. 2012

Self Cite

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Graphene oxide, a two-dimensional aromatic scaffold decorated by oxygen-containing functional groups, possesses rich chemical properties and may present a green alternative to precious metal catalysts. Graphene oxide-based carbocatalysis has recently been demonstrated for aerobic oxidative reactions. However, its widespread application is hindered by the need for high catalyst loadings. Here we report a simple chemical treatment that can create and enlarge the defects in graphene oxide and impart on it enhanced catalytic activities for the oxidative coupling of amines to imines (up to 98% yield at 5 wt% catalyst loading, under solvent-free, open-air conditions). This study examines the origin of the enhanced catalytic activity, which can be linked to the synergistic effect of carboxylic acid groups and unpaired electrons at the edge defects. The discovery of a simple chemical processing step to synthesize highly active graphene oxide allows the premise of industrial-scale carbocatalysis to be explored.

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“…We experimentally reported it at the hydrogen (H)-terminated pore edges of low-defect graphene nanomeshes (GNMs: Figure 1(a)) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], which were fabricated using non-lithographic method (i.e., nanoporous alumina templates as etching masks [11]), by observing the ferromagnetism (i.e., ferromagnetic GNMs (FM-FNMs)) [1][2][3][4][5][6][7][8][9], the distribution of the polarized edge spins by magnetic force microscope [10], and some spin-based phenomena [10][11][12][13][14][15]. The spin polarization appeared because of the low-defect zigzag atomic structure of the pore edges [1][2][3][4][5][6][7] formed by edge reconstruction caused by critical-temperature annealing [12][13][14] and the assembly of narrow interpore regions (e.g., 10 ~ 20 nm width) corresponding to H-terminated zigzag graphene nanoribbons (GNRs: one-dimensional strip lines of graphene with edges on both longitudinal sides; Figure ...…”

Section: Introductionmentioning

confidence: 99%

Electronic Properties of Nanopore Edges of Ferromagnetic Graphene Nanomeshes at High Carrier Densities under Ionic-Liquid Gating

Hashimoto¹,

Kamikawa²,

Yagi³

et al. 2014

MSA

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Graphene edges with a zigzag-type atomic structure can theoretically produce spontaneous spin polarization despite being a critical-metal-free material. We have demonstrated this in graphene nanomeshes (GNMs) with honeycomb-like arrays of low-defect hexagonal nanopores by observing room-temperature ferromagnetism and spin-based phenomena arising from the zigzag-pore edges. Here, we apply extremely high electric fields to the ferromagnetic (FM) GNMs using an ionic-liquid gate. A large on/off-ratio for hole current is observed for even small applied ionic-liquid gate voltages (V ig ). Observations of the magnetoresistance behavior reveal high carrier densities of ~10 13 cm −2 at large V ig values. We find a maximum conductance peak in the high −V ig region and its separation into two peaks upon applying a side-gate (in-plane external) voltage (V ex ). It is discussed that localized edge-π band with excess-density electrons induced by V ig and its spin splitting for majority and minority of spins by V ex (half-metallicity model) lead to these phenomena. The results must realize critical-element-free novel spintronic devices.

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The edge state of nanographene and the magnetism of the edge-state spins

Cited by 126 publications

References 56 publications

Manipulation of edge magnetism in hexagonal graphene nanoflakes

Manipulation of edge magnetism in hexagonal graphene nanoflakes

Probing the catalytic activity of porous graphene oxide and the origin of this behaviour

Electronic Properties of Nanopore Edges of Ferromagnetic Graphene Nanomeshes at High Carrier Densities under Ionic-Liquid Gating

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