Room temperature ferromagnetism in partially hydrogenated epitaxial graphene

Xie, Lanfei; Wang, Xiao; Lu, Jiong; Ni, Zhenhua; Luo, Zhiqiang; Mao, Hongying; Wang, Rui; Wang, Yingying; Huang, Han; Qi, Dongchen; Liu, Rong; Yu, Ting; Shen, Zexiang; Wu, Tom; Peng, Haiyang; Özyilmaz, Barbaros; Loh, Kian Ping; Wee, Andrew Thye Shen; Ariando, Ariando; Chen, Wei

doi:10.1063/1.3589970

Cited by 140 publications

(117 citation statements)

References 30 publications

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“…1,7,[36][37][38][39][40][41][42] In particular, there have been several reports of ferromagnetic ordering in graphene and graphite. [36][37][38][39][40][41] However, theoretically, the ferromagnetic ordering in realistic experiments is not well understood. 1 Magnetometry measurements have the advantage of directly measuring the total magnetic moment, but are subject to artifacts.…”

Section: Magnetic Moment Formation and Exchange Fields In Graphementioning

confidence: 99%

Integrating MBE materials with graphene to induce novel spin-based phenomena

Swartz¹,

McCreary²,

Han³

et al. 2013

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Magnetism in graphene is an emerging field that has received much theoretical attention. In particular, there have been exciting predictions for induced magnetism through proximity to a ferromagnetic insulator as well as through localized dopants and defects. Here, we discuss our experimental work using molecular beam epitaxy (MBE) to modify the surface of graphene and induce novel spin-dependent phenomena. First, we investigate the epitaxial growth the ferromagnetic insulator EuO on graphene and discuss possible scenarios for realizing exchange splitting and exchange fields by ferromagnetic insulators. Second, we investigate the properties of magnetic moments in graphene originating from localized p z -orbital defects (i.e. adsorbed hydrogen atoms). The behavior of these magnetic moments is studied using non-local spin transport to directly probe the spin-degree of freedom of the defect-induced states. We also report the presence of enhanced electron g-factors caused by the exchange fields present in the system. Importantly, the exchange field is found to be highly gate dependent, with decreasing g-factors with increasing carrier densities.

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Section: Magnetic Moment Formation and Exchange Fields In Graphementioning

confidence: 99%

Integrating MBE materials with graphene to induce novel spin-based phenomena

Swartz¹,

McCreary²,

Han³

et al. 2013

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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“…For example, adsorbed F atoms produce a significant magnetic moment on the graphene C atoms 11 , as can hydrogenation 12 . Adatoms also influence the electronic properties of graphene 13 , e. g., by shifting the energy of the Dirac point, changing the density of states near that point, and altering electron and hole mobility 9 .…”

mentioning

confidence: 99%

Clustering and magnetic anisotropy of Fe adatoms on graphene

Porter

Stroud

2012

Phys. Rev. B

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Single Fe adatoms and clusters of Fe adatoms on graphene are studied through first-principles calculations using density functional theory (DFT) and spin density functional theory (sDFT).First, we consider computational cells containing various numbers of C atoms and one Fe adatom.We calculate the binding energy, adatom height, and magnetic moment of the adatom above a few high-symmetry positions in the cell. In all cases, the binding energy increases with decreasing cell size, suggesting that clustering of the Fe adatoms is energetically favored. We also calculate the energy of various clusters of two to four Fe atoms on graphene in computational cells of various sizes, using both DFT and sDFT. These calculations again show that, both in DFT and sDFT, the Fe adatoms strongly prefer to form clusters. The energy barrier for an isolated Fe adatom to diffuse from the center of one graphene hexagon is calculated to be 0.49 eV. This barrier is reduced for an Fe atom which is one of a pair of neighboring adatoms. Finally, by including spin-orbit interactions within sDFT, we calculate the magnetic anisotropy energy of a single Fe adatom on graphene. We find that the in-plane anisotropy energy is close to zero, while the out-of-plane anisotropy energy is ∼ DS 2 cos 2 θ where S ∼ 2.0, θ is the angle between the magnetic moment and the perpendicular to the graphene plane, and D ∼ 0.25 meV.

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“…In this context, considerable effort has recently been directed to rendering graphene ferromagnetic via chemical modification. Thus far, ferromagnetic order in graphene has been attained through covalent functionalization, involving the linkage of radical species like the spin-bearing carbon atom of an organic molecule or hydrogen atoms to the graphene layer [5][6][7][8][9][10][11][12][13][14][15][16][17] . Along these lines, functionalization of epitaxial graphene by aryl radicals has been reported to yield disordered magnetism, comprising a mixture of ferromagnetic, superparamagnetic and antiferromagnetic regions 18 .…”

mentioning

confidence: 99%

Interface-Induced Room-Temperature Ferromagnetism in Hydrogenated Epitaxial Graphene

et al. 2013

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Due to the predominantly surface character of graphene, it is highly suitable for functionalization with external atoms and/or molecules leading to a plethora of new and interesting phenomena. Here we show ferromagnetic properties of hydrogenfunctionalized epitaxial graphene on SiC. Ferromagnetism in such a material is not directly evident as it is inherently composed of only non-magnetic constituents. Our results nevertheless show strong ferromagnetism, which cannot be explained by simple magnetic impurities. The ferromagnetism is unique to hydrogenated epitaxial graphene on SiC, where interactions with the interfacial buffer layer play a crucial role. We argue that the origin of the observed ferromagnetism is governed by electron correlation effects of the narrow Si-dangling-bond (Si-DB) states in the buffer layer exchangecoupled to localized states in the hydrogenated graphene layer. This forms a quasithree-dimensional ferromagnet with a Curie temperature higher than 300 K.Owing to its capability of ballistic transport over micrometer distances 1 , as well as its very long spin relaxation time and spin relaxation length 2, 3 , graphene represents a close-to-ideal material for spintronic applications 4 . In this context, considerable effort has recently been directed to rendering graphene ferromagnetic via chemical modification. Thus far, ferromagnetic order in graphene has been attained through covalent functionalization, involving the linkage of radical species like the spin-bearing carbon atom of an organic molecule or hydrogen atoms to the graphene layer [5][6][7][8][9][10][11][12][13][14][15][16][17] . Along these lines, functionalization of epitaxial graphene by aryl radicals has been reported to yield disordered magnetism, comprising a mixture of ferromagnetic, superparamagnetic and antiferromagnetic regions 18 .With the aid of combined atomic and magnetic force microscopy, it could be proven that these randomly dispersed regions are constituted by the attached moieties. This lack of a periodic functionalization pattern of the graphene sheet prevents the achievement of long range ferromagnetic order, thus limiting the use of such samples in spintronic devices.Furthermore, room temperature ferromagnetism has been detected in partially hydrogenated epitaxial graphene grown on silicon carbide (SiC), and attributed to hydrogen monomers bonded to the graphene sheet 12 . Despite these accomplishments, however, both the mechanism underlying the ferromagnetic ordering, and the role played by the SiC substrate used for the epitaxial graphene growth, has not yet been clarified. Here, we experimentally demonstrate that spin ordering within hydrogenated epitaxial graphene critically depends on the presence of the underlying buffer layer. In addition, it is shown that the created magnetic 3 areas are distributed over the entire graphene sheet, thus enabling to effectively tune the overall magnetization through the density of attached hydrogen atoms.To explore the ferromagnetism in epitaxial graphene, we use samples ...

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Room temperature ferromagnetism in partially hydrogenated epitaxial graphene

Cited by 140 publications

References 30 publications

Integrating MBE materials with graphene to induce novel spin-based phenomena

Integrating MBE materials with graphene to induce novel spin-based phenomena

Clustering and magnetic anisotropy of Fe adatoms on graphene

Interface-Induced Room-Temperature Ferromagnetism in Hydrogenated Epitaxial Graphene

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