Ferromagnetism in oriented graphite samples

Esquinazi, P.; Setzer, A.; Höhne, R.; Semmelhack, C.; Kopelevich, Y.; Spemann, D.; Butz, T.; Kohlstrunk, B.; Lösche, Mathias

doi:10.1103/physrevb.66.024429

Cited by 381 publications

(327 citation statements)

References 36 publications

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“…Therefore, such measurements are performed on solutions of graphene processed by various techniques, including unzipping carbon nanotubes whose grow very often requires ferromagnetic catalyst. Therefore, the observation of room temperature ferromagnetism in graphene ribbons 107 should be revised under the light of the recently work 108 discussing artifacts for analogous claims for highly oriented pyrolitic graphite 109 .…”

Section: A Zigzag Edge States and Edge Magnetismmentioning

confidence: 99%

Edge states in graphene-like systems

2015

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The edges of graphene and graphene like systems can host localized states with evanescent wave function with properties radically different from those of the Dirac electrons in bulk. This happens in a variety of situations, that are reviewed here. First, zigzag edges host a set of localized non dispersive state at the Dirac energy. At half filling, it is expected that these states are prone to ferromagnetic instability, causing a very interesting type of edge ferromagnetism. Second, graphene under the influence of external perturbations can host a variety of topological insulating phases, including the conventional Quantum Hall effect, the Quantum Anomalous Hall (QAH) and the Quantum Spin Hall phase, in all of which phases conduction can only take place through topologically protected edge states. Here we provide an unified vision of the properties of all these edge states, examined under the light of the same one orbital tight-binding model. We consider the combined action of interactions, spin orbit coupling and magnetic field, which produces a wealth of different physical phenomena. We briefly address what has been actually observed experimentally.

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Section: A Zigzag Edge States and Edge Magnetismmentioning

confidence: 99%

Edge states in graphene-like systems

2015

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“…Scanning tunneling microscopy (STM) measurements have been performed at linear step edges at the surface of highly oriented pyrolytic graphite (HOPG). 11,12 So far, the (…”

Section: Introductionmentioning

confidence: 99%

“…11,12 Here, we investigated the LDOS in the vinicity of linear step edges of both the zigzag and armchair types with STM/STS. A Brief Report of the STS observation of the graphite edge state has been already made elsewhere.…”

Section: Introductionmentioning

confidence: 99%

Scanning tunneling microscopy and spectroscopy of the electronic local density of states of graphite surfaces near monoatomic step edges

et al. 2006

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We measured the electronic local density of states (LDOS) of graphite surfaces near monoatomic step edges, which consist of either the zigzag or armchair edge, with the scanning tunneling microscopy (STM) and spectroscopy (STS) techniques. The STM data reveal that the (and honeycomb superstructures coexist over a length scale of 3−4 nm from both the edges. By comparing with density-functional derived nonorthogonal tight-binding calculations, we show that the coexistence is due to a slight admixing of the two types of edges at the graphite surfaces. In the STS measurements, a clear peak in the LDOS at negative bias voltages from −100 to −20 mV was observed near the zigzag edges, while such a peak was not observed near the armchair edges. We concluded that this peak corresponds to the graphite "edge state" theoretically predicted by Fujita et al. [J. Phys. Soc. Jpn. 65, 1920] with a tight-binding model for graphene ribbons. The existence of the edge state only at the zigzag type edge was also confirmed by our first-principles calculations with different edge terminations.

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“…A number of recent experiments suggest that pure graphite behaves as a highly correlated electron system [1]. In particular it shows a metalinsulator transition in magnetic fields and insulating behavior in the direction perpendicular to the planes in different samples [1,2,3,4,5,6,7,8]. Recent results show ferromagnetic behavior [9], enhanced by proton bombardment [10], what opens up a new way to the creation of organic magnets [11].…”

mentioning

confidence: 99%

Local defects and ferromagnetism in graphene layers

et al. 2005

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We study the changes in the electronic structure induced by lattice defects in graphene planes. In many cases, lattice distortions give rise to localized states at the Fermi level. Electron-electron interactions lead to the existence of local moments. The RKKY interaction between these moments is always ferromagnetic, due to the semimetallic properties of graphene.PACS numbers: 75.10. Jm, 75.10.Lp, 75.30.Ds Introduction. A number of recent experiments suggest that pure graphite behaves as a highly correlated electron system [1]. In particular it shows a metalinsulator transition in magnetic fields and insulating behavior in the direction perpendicular to the planes in different samples [1,2,3,4,5,6,7,8]. Recent results show ferromagnetic behavior [9], enhanced by proton bombardment [10], what opens up a new way to the creation of organic magnets [11]. In this paper we study the formation of local moments near simple defects. It is shown that many tyoes of lattice distortions, like cracks and vacancies, can induce localized states at the Fermi level, leading to the existence of local moments. The RKKY interaction between these moments is always ferromagnetic due to the semimetallic properties of graphite. Hence, the RKKY interaction does not lead to frustration and spin glass features.The model. The conduction band of graphite is well described by a tight binding model which includes the π orbitals which are perpendicular to the graphite planes at each C atom [12]. If the interplane hopping is neglected, this model describes a semimetal, with zero density of states at the Fermi energy, and where the Fermi surface is reduced to two inequivalent K-points located at the corner of the hexagonal Brillouin Zone. The low-energy excitations with momenta in the vicinity of the Fermi points have a linear dispersion and can be described by a continuum model which reduces to the Dirac equation in two dimensions [12,13,14,15,16]. The Hamiltonian density of the system is

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Ferromagnetism in oriented graphite samples

Cited by 381 publications

References 36 publications

Edge states in graphene-like systems

Edge states in graphene-like systems

Scanning tunneling microscopy and spectroscopy of the electronic local density of states of graphite surfaces near monoatomic step edges

Local defects and ferromagnetism in graphene layers

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