<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>π</mml:mi></mml:math>-Electron Ferromagnetism in Metal-Free Carbon Probed by Soft X-Ray Dichroism

Ohldag, Hendrik; Tyliszczak, Tolek; Höhne, R.; Spemann, D.; Esquinazi, P.; Ungureanu, Mariana; Butz, T.

doi:10.1103/physrevlett.98.187204

Cited by 281 publications

(224 citation statements)

References 19 publications

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“…Ferromagnetism in carbon has been observed near the surface in proton-and carbon ion-irradiated HOPG, where its origin was linked to p-electrons and hydrogen-defect complexes. [14] Ferromagnetism has been predicted theoretically [15] in bulk carbon containing 50 pct sp 2 -and 50 pct sp 3 -hybridized carbon. The structure of this ferromagnetic phase is predicted to be rhombic type (a = 0.2608 nm, b = 0.3961 nm, c = 0.5289 nm with a = b = c = 90°), which is intermediate between the graphite and diamond structure with mass density of 2.9 g cm À3 ).…”

Section: R E T R a C T E D A R T I C L Ementioning

confidence: 99%

RETRACTED ARTICLE: Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

Narayan

2016

Metall Mater Trans A

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We review the discovery of new phases of carbon (Q-carbon) and BN (Q-BN) and address critical issues related to direct conversion of carbon into diamond and hBN into cBN at ambient temperatures and pressures in air without any need for catalyst and the presence of hydrogen. The Q-carbon and Q-BN are formed as a result of quenching from super undercooled state by using high-power nanosecond laser pulses. We discuss the equilibrium phase diagram (P vs T) of carbon, and show that by rapid quenching, kinetics can shift thermodynamic graphite/diamond/liquid carbon triple point from 5000 K/12 GPa to super undercooled carbon at atmospheric pressure in air. Similarly, the hBN-cBN-Liquid triple point is shifted from 3500 K/9.5 GPa to as low as 2800 K and atmospheric pressure. It is shown that nanosecond laser heating of amorphous carbon and nanocrystalline BN on sapphire, glass, and polymer substrates can be confined to melt in a super undercooled state. By quenching this super undercooled state, we have created a new state of carbon (Q-carbon) and BN (Q-BN) from which nanocrystals, microcrystals, nanoneedles, microneedles, and thin films are formed depending upon the nucleation and growth times allowed and the presence of growth template. The large-area epitaxial diamond and cBN films are formed, when appropriate planar matching or lattice matching template is provided for growth from super undercooled liquid. The Q-phases have unique atomic structure and bonding characteristics as determined by high-resolution SEM and backscatter diffraction, HRTEM, STEM-Z, EELS, and Raman spectroscopy, and exhibit new and improved mechanical hardness, electrical conductivity, and chemical and physical properties, including room-temperature ferromagnetism and enhanced field emission. The Q-carbon exhibits robust bulk ferromagnetism with estimated Curie temperature of about 500 K and saturation magnetization value of 20 emu g À1 . We have also deposited diamond on cBN by using a novel pulsed laser evaporation of carbon and obtained cBN/diamond composites, where cBN acts as template for diamond growth. Both diamond and cBN grown from super undercooled liquid can be alloyed with both p-and n-type dopants. This process allows carbon to diamond and hBN to cBN conversions and formation of useful nanostructures and microstructures at ambient temperatures in air at atmospheric pressure on practical and heat-sensitive substrates in a controlled way without need for any catalysts and hydrogen to stabilize sp 3 bonding for diamond and cBN phases.

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Section: R E T R a C T E D A R T I C L Ementioning

confidence: 99%

RETRACTED ARTICLE: Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

Narayan

2016

Metall Mater Trans A

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“…In resent theoretical works was described the vacancies 11 or chemical doping 12 of C 60 as a case of ferromagnetism. Received results qualitatively correspond with experimentally observed magnetism on carbon in proton irradiated graphite 13 and Fe/C multilayers. 14 In [12] was detailed studying distribution on magnetisation on fullerene cage and shown that magnetic moments distributed on shell equivalently.…”

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confidence: 86%

Magnetic Properties of Ni(II) Complexes of (hydrazone)imine 1,2,3-triketones: Intramolecular Exchange Interaction

Shvachko

Starichenko

Королев

et al. 2007

3rd France-Russia Seminar

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We carry out comparative study of electronic structure, magnetic and resonance properties of three novel tetracyclic Ni(II) The magnetic properties of molecular crystals based on nickel complexes are of particular inter est. Bis chelate NiII complexes containing the central NiN 4 fragment, in which the metal atom is in a square planar ligand environment (coordination number is 4), are known to be diamagnetic. 5 In these complexes, the ligand environment can be formed, in particular, by different 1,2 diamines used as the starting organic compounds, which, depending on the synthesis conditions, are either involved in the complex in the initial form or oxidized to give semidiimines or diimines-2,3 The geometry of the resulting metal chelate NiN 4 unit can be controlled by varying the electronic and steric characteristicsof chelate ligands is such systems, thus resulting in considerable deviations from the planar geometry, which can give rise to paramagnetism. On Fig. 1 presented chemical structure of studied complexes. Details of synthesis and geometrical structure of studied complexes reported in [3]. In the complex 1 Ni ion is in four N tetrahedral environment, in the complex 2 Ni ion is also coordinated by four N but they form a plane square, in the complex 3 Ni ions is in tetrahedral environment containing two O and two N. Described differences in local environment of Ni ion produce a different magnetic properties Names 2007, 3rd France-Russia Seminar

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“…Ideal graphene sheet is nonmagnetic, then to use graphene for spintronic applications the major challenge is to make graphene magnetic. In this sense, the experimental observation of magnetic properties in graphene and related materials [4][5][6][7][8] has drawn huge interest, especially considering the applications of these materials in spintronics, quantum information processing and others.…”

Section: Introductionmentioning

confidence: 99%

Interaction between single vacancies in graphene sheet: An ab initio calculation

Scopel¹,

Paz²,

Freitas³

2016

Solid State Communications

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In order to investigate the interaction between single vacancies in a graphene sheet, we have used spin-polarized density functional theory (DFT). Two distinct configurations were considered, either with the two vacancies located in the same sublattice or in different sublattices, and the effect of changing the separation between the vacancies was also studied. Our results show that the ground state of the system is indeed magnetic, but the presence of the vacancies in the same sublattice or in different sublattices and the possible topological configurations can lead to different contributions from the π and σ orbitals to magnetism. On the other hand, our findings reveal that the net magnetic moment of the system with the two vacancies in the same sublattice move towards the value of the magnetic moment per isolated vacancy with the increase of the distance between the vacancies, which is ascribed to the different contributions due to π electrons. Moreover, it is also found that the local magnetic moments for vacancies in the same sublattice are in parallel configuration, while they have different orientations when the vacancies are created in different sublattices. So, our findings have clearly evidenced how difficult it would be to observe experimentally the emergence of magnetic order in graphene-based systems containing randomly created atomic vacancies, since the energy difference between cases of antiferromagnetic and ferromagnetic order decreases quickly with the increase in the distance separating each vacancy pair.

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π-Electron Ferromagnetism in Metal-Free Carbon Probed by Soft X-Ray Dichroism

Cited by 281 publications

References 19 publications

RETRACTED ARTICLE: Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

RETRACTED ARTICLE: Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

Magnetic Properties of Ni(II) Complexes of (hydrazone)imine 1,2,3-triketones: Intramolecular Exchange Interaction

Interaction between single vacancies in graphene sheet: An ab initio calculation

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