Structure and magnetism of disordered carbon

Akhukov, Mikhail A.; Katsnelson, M. I.; Fasolino, A.

doi:10.1088/0953-8984/25/25/255301

Cited by 3 publications

(3 citation statements)

References 52 publications

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“…From this viewpoint the CNT matrix is of special interest. Defectless carbon based materials are diamagnetic, while by introducing different kinds of defects and disorder in them, one sees paramagnetic or even ferromagnetic behavior [14][15][16][17]. However, in carbon based materials saturation magnetization M sat is not large enough for practical applications of magnetic carbon devices.…”

Section: Introductionmentioning

confidence: 99%

Manifestation of coherent magnetic anisotropy in a carbon nanotube matrix with low ferromagnetic nanoparticle content

et al. 2015

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Section: Introductionmentioning

confidence: 99%

Manifestation of coherent magnetic anisotropy in a carbon nanotube matrix with low ferromagnetic nanoparticle content

et al. 2015

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“…In amorphous carbon/activated carbon fibers there are two theories as to the origin of magnetic spins: the disorder creates a glassy-like magnetism which can be attributed to free/non-bonded π electrons such as dangling bonds [20] or the mixing of sp 2 and sp 3 carbon atoms which are dependent on atomic configurations [20][21][22]. In both cases the mechanism by which magnetism can arise is similar: disorder creates electrons with unpaired spins.…”

Section: -Magnetism In Disordered Carbonmentioning

confidence: 99%

“…Considering the similarities of the carbon nanofoams with pyrolysis treated amorphous carbon, it is surprising these samples do not show ferromagnetic interactions. In the carbon nanofoam, the small (6-7 graphitic rings) sp 2 regions are isolated and it is believed this makes spins difficult to align [20,21]. However, no direct experimental correlation between the magnetism and the graphite structures has been made, making definitive statements regarding how magnetism arises from disorder impossible.…”

Section: -Magnetism In Disordered Carbonmentioning

confidence: 99%

Exploring defects and induced magnetism in epitaxial graphene films

Mazza¹

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Graphene has been demonstrated to have unique properties not only in its virgin state but also by altering its environment through rotations in bilayer graphene, doping, and creating heterostructures with other 2D materials, which all lead to different functional behaviors. Another avenue to altering graphene is by using defects to generate p-orbital magnetism, which is of interest both to fundamental physics and potential application in new classes of spintronic devices. Indeed, atomic hydrogen creating sp3 defects attached to the graphene surface as well as vacancies in graphene have been shown to induce magnetism, while high energy (MeV) proton irradiation has been shown to produce ferromagnetism at room-temperature in graphite. However, detailed investigations of these systems are absent so that little is known about the density and configuration of defects, the role of interfaces, or how these relate to magnetism. In this thesis studies of single-layer graphene revealed that atomic deuteration indeed does lead to reversible chemisorption. However, it is found that atomic deuterium treatment of many-layer epitaxially grown graphene on C-face 4H-SiC (EG/SiC) only affects the surface graphene layer and the buried graphene/SiC interface. While this result did not present magnetism from the interface or graphene, x-ray reflectivity and cross-sectional transmission electron microscopy demonstrated a change of the buried graphene/SiC interface which resembles a delamination of graphene from the substrate. In some cases, multiple atomic treatments lead to complete delamination of the graphene film. Motivated by the results of atomic hydrogenation (deuteration), interlayer incorporation of hydrogen was achieved by accelerating ions to implant them between graphene sheets using low (100s of eV) energy hydrogen ion implantation. We focus on addressing the role of the damage from implantation in the magnetism which we observe in our samples. The use of polarized neutron reflectivity and x-ray scattering aims to uniquely address the relationship of strain, structural damage or chemisorption, and magnetism in many layer epitaxial graphene. We find that via tailoring the ion distribution (and range) to the sample we can reliably predict the structural and magnetic changes driven by implantation.

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THEMIS 2.0: A self-consistent model for dust extinction, emission, and polarisation

Ysard,

Jones,

Guillet

et al. 2024

A&A

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Recent observational constraints in emission, extinction, and polarisation have at least partially invalidated most of the astronomical standard grain models for the diffuse interstellar medium. Moreover, laboratory measurements on interstellar silicate analogues have shown quite significant differences with the optical properties used in these standard models. To address these issues, our objective is twofold: (i) to update the optical properties of silicates and (ii) to develop The Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS) to allow the calculation of polarised extinction and emission. Based on optical constants measured in the laboratory from $5 to 1 mm for amorphous silicates and on observational constraints in mid-IR extinction and X-ray scattering, we defined new optical constants for the THEMIS silicates. Absorption and scattering efficiencies for spheroidal grains using these properties were subsequently derived with the discrete dipole approximation. These new optical properties make it possible to explain the dust emission and extinction, both total and polarised. It is noteworthy that the model is not yet pushed to its limits since it does not require the perfect alignment of all grains to explain the observations and it therefore has the potential to accommodate the highest polarisation levels inferred from extinction measurements. Moreover, the dispersion of the optical properties of the different silicates measured in the laboratory naturally explain the variations in both the total and polarised emission and extinction observed in the diffuse interstellar medium. A single, invariant model calibrated on one single set of observations is obsolete for explaining contemporary observations. We are proposing a completely flexible dust model based entirely on laboratory measurements that has the potential to make major advances in understanding the exact nature of interstellar grains and how they evolve as a function of their radiative and dynamic environment. Even if challenging, this is also relevant for future cosmic microwave background (CMB) missions that will aim to perform precise measurements of the CMB spectral distortions and polarisation.

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Structure and magnetism of disordered carbon

Cited by 3 publications

References 52 publications

Manifestation of coherent magnetic anisotropy in a carbon nanotube matrix with low ferromagnetic nanoparticle content

Manifestation of coherent magnetic anisotropy in a carbon nanotube matrix with low ferromagnetic nanoparticle content

Exploring defects and induced magnetism in epitaxial graphene films

THEMIS 2.0: A self-consistent model for dust extinction, emission, and polarisation

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