The role of hydrogen in room-temperature ferromagnetism at graphite surfaces

Ohldag, Hendrik; Esquinazi, P.; Arenholz, Elke; Spemann, D.; Rothermel, Martin; Setzer, A.; Butz, T.

doi:10.1088/1367-2630/12/12/123012

Cited by 123 publications

(128 citation statements)

References 28 publications

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“…It is generally accepted that chemisorption of a single hydrogen atom leads to the appearance of a defect-induced magnetic moment on the graphene sheet, along with a large structural distortion [19][20][21]. Recently, Ohldag et al [24] have discussed the role of hydrogen in room-temperature ferromagnetism at graphite surfaces from an x-ray dichroism analysis.…”

Section: Introductionmentioning

confidence: 99%

Diffusion of hydrogen in graphite: a molecular dynamics simulation

Herrero¹,

Ramı́rez²

2010

J. Phys. D: Appl. Phys.

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Diffusion of atomic and molecular hydrogen in the interstitial space between graphite sheets has been studied by molecular dynamics simulations. Interatomic interactions were modeled by a tight-binding potential fitted to density-functional calculations. Atomic hydrogen is found to be bounded to C atoms, and its diffusion consists in jumping from a C atom to a neighboring one, with an activation energy of about 0.4 eV. Molecular hydrogen is less attached to the host sheets and diffuses faster than isolated H. At temperatures lower than 500 K, H 2 diffuses with an activation energy of 89 meV, whereas at higher T its diffusion is enhanced by longer jumps of the molecule as well as by correlations between successive hops, yielding an effective activation energy of 190 meV.

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Section: Introductionmentioning

confidence: 99%

Diffusion of hydrogen in graphite: a molecular dynamics simulation

Herrero¹,

Ramı́rez²

2010

J. Phys. D: Appl. Phys.

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“…Ion irradiation can be used to introduce structural defects in graphene and other carbon allotropes 16 , and provides a versatile tool for manipulating their physical properties 7,[17][18][19][20][21][22] For this purpose, proton irradiation, in particular, attracts much interest due to the observed irradiation-induced magnetism in graphite and graphene [23][24][25][26][27][28][29] , which was attributed to defects, e.g., vacancies and H species 24 . However, an atomic-resolved determination, e.g.…”

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confidence: 99%

“…It is still unclear whether defects can be generated at a higher proton energy. Moreover, to mimic proton irradiation in various experiments 23,28,29 where fast H + ions with kinetic energy ranging from a few hundred keV to a few MeV were used, it would be very valuable to extend the simulations to that energy range and also explore the effect of the charge state of the projectile.…”

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confidence: 99%

Simulation of high-energy ion collisions with graphene fragments

et al. 2012

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The collision of energetic ions and graphene fragments is studied in the framework of real-space finite-difference time-dependent density functional theory (TDDFT) coupled with classical molecular dynamics for nuclei. The amount of energy transferred from the projectile to the target is calculated to explore the defect formation mechanisms as a function of the projectile's energy. It is found that creation of defects in graphene due to the interaction of a fast proton with valence electrons is unlikely. In the case of projectiles with higher charges the transferred energy increases significantly, leading to higher probability of bond breaking.

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“…2 Carbon allotropes show diamagnetism, 3 paramagnetism, 4 ferromagnetism, [5][6][7] and antiferromagnetism 8 whereby a carbon sample may show a magnetization consisting of a mixture of the previous effects. For example, point defects in graphene laminates 9 induce additional spin-half paramagnetisms to basal diamagnetisms.…”

Section: Introductionmentioning

confidence: 99%

“…In highly ordered pyrolytic graphite (HOPG) samples irradiated by protons, ferromagnetic order was found using magnetization measurements 6 and x-ray dichroism method. 7 However, HOPG samples irradiated by neutrons, 11 where point defects are close enough to create long-ranged ferromagnetic ordering, showed free spin paramagnetisms.…”

Section: Introductionmentioning

confidence: 99%

Magnetic properties of graphene nanodisk and nanocone powders at low temperatures

et al. 2015

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Our aim is the study of magnetization phenomena of carbon powders consisting of graphene nanocones and nanodisks. Magnetization measurements were carried out using a superconducting quantum interference devices in magnetic fields −5 < B < 5 T for temperatures in the range 0.5 ≤ T < 300 K. We have observed that magnetization M depends on temperature T as a power law M ∝ T −α where the scaling exponent α = 0.79 ± 0.04 was determined. We found that the magnetization consists of a diamagnetic background and a paramagnetic contribution of localized spins. Considering saturation magnetization M S in the free spin magnetization model and diamagnetic susceptibility χ D for independent of temperature T we found that the effective spin value S increases from S = 1/2 at temperature T > 20 K to S = 3 at low temperatures 0.5 ≤ T ≤ 20 K.2

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The role of hydrogen in room-temperature ferromagnetism at graphite surfaces

Cited by 123 publications

References 28 publications

Diffusion of hydrogen in graphite: a molecular dynamics simulation

Diffusion of hydrogen in graphite: a molecular dynamics simulation

Simulation of high-energy ion collisions with graphene fragments

Magnetic properties of graphene nanodisk and nanocone powders at low temperatures

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