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Kopelevich, Y.; Esquinazi, P.; Torres, J. H. S.; Moehlecke, S.

doi:10.1023/a:1004637814008

Cited by 261 publications

(232 citation statements)

References 17 publications

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“…These hysteresis loops are typical of FM materials and are similar to those observed before [1] in HOPG graphite samples. The FM behavior of both HOPG and C-S persists well above the room temperature [1,2].…”

supporting

confidence: 84%

“…The superconducting state coexists with the ferromagnetism of pure graphite, and a continuous crossover from superconducting to ferromagnetic-like behavior could be achieved by increasing the magnetic field or the temperature. The angular dependence of the magnetic moment m(α) provides evidence for an interaction between the ferromagnetic and the superconducting order parameters.An interplay between ferromagnetic (FM) and superconducting (SC) behavior of graphite and related systems has recently been observed [1,2] and theoretically analyzed [3,4]. In particular, it has been demonstrated that the SC of graphite-sulfur (C-S) composites occurring within some sort of "grains" or domains [5,2] is highly anisotropic and associated with the graphite planes [2].…”

mentioning

confidence: 99%

“…In particular, it has been demonstrated that the SC of graphite-sulfur (C-S) composites occurring within some sort of "grains" or domains [5,2] is highly anisotropic and associated with the graphite planes [2]. The SC domains coexist with the FM of pure graphite [1], and a continuous crossover from SC to FM-like behavior could be achieved increasing either the applied magnetic field H or the temperature T.Here we focus our attention on the highly anisotropic nature of the SC state of the C-S composites, which was explored by means of the angular dependence of the sample magnetic moment m(α, T, H), where α is the angle between the applied magnetic field H and the largest sample surface. The main conclusion of this work is that SC and FM order parameters interact in such a way that the FM component of m(α, T, H) is rotated by 90 • below the SC transition temperature T c (H).…”

mentioning

confidence: 99%

“…An interplay between ferromagnetic (FM) and superconducting (SC) behavior of graphite and related systems has recently been observed [1,2] and theoretically analyzed [3,4]. In particular, it has been demonstrated that the SC of graphite-sulfur (C-S) composites occurring within some sort of "grains" or domains [5,2] is highly anisotropic and associated with the graphite planes [2].…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Local superconductivity and ferromagnetism interplay in graphite-sulfur composites

Moehlecke¹,

Kopelevich²,

Maple³

2003

Braz. J. Phys.

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The superconductivity of graphite-sulfur composites is highly anisotropic and associated with the graphite planes. The superconducting state coexists with the ferromagnetism of pure graphite, and a continuous crossover from superconducting to ferromagnetic-like behavior could be achieved by increasing the magnetic field or the temperature. The angular dependence of the magnetic moment m(α) provides evidence for an interaction between the ferromagnetic and the superconducting order parameters.An interplay between ferromagnetic (FM) and superconducting (SC) behavior of graphite and related systems has recently been observed [1,2] and theoretically analyzed [3,4]. In particular, it has been demonstrated that the SC of graphite-sulfur (C-S) composites occurring within some sort of "grains" or domains [5,2] is highly anisotropic and associated with the graphite planes [2]. The SC domains coexist with the FM of pure graphite [1], and a continuous crossover from SC to FM-like behavior could be achieved increasing either the applied magnetic field H or the temperature T.Here we focus our attention on the highly anisotropic nature of the SC state of the C-S composites, which was explored by means of the angular dependence of the sample magnetic moment m(α, T, H), where α is the angle between the applied magnetic field H and the largest sample surface. The main conclusion of this work is that SC and FM order parameters interact in such a way that the FM component of m(α, T, H) is rotated by 90 • below the SC transition temperature T c (H).The here studied graphite-sulfur sample was thoroughly characterized in Ref. [2]. In summary, the C-S sample was prepared using graphite rods from Carbon of America Ultra Carbon, AGKSP grade, ultra "F" purity (99.9995%) (AlfaAesar, # 40766) and sulfur chunks from American Smelting and Refining Co. that are spectrographically pure (99.999+ %). A pressed pellet (φ = 6 mm, ∼7000 lb) of graphite was prepared by pressing graphite powder, the graphite powder was produced by cutting and grinding the graphite rod on the edge and side area of a new and clean circular diamond saw blade. The graphite pellet was encapsulated with sulfur chunks (mass ratio ∼ 1:1) in quartz tube under 1/2 atmosphere of argon and heat treated in a tube furnace at 400 • C for one hour and then slowly cooled (4 • C/h) to room temperature. X-ray diffraction measurements (θ-2θ geometry and rocking curves) of the reacted sample yielded a spectrum with only the superposition of the (00 ) diffraction peaks of graphite with the orthorhombic peaks of sulfur with no extra peak due to a compound, second phase or impurity. The c-axis lattice parameter (c = 6.72Å) of the sample is equal to the pristine graphite powder pellet, which testifies against sulfur intercalation. The diffraction pattern also shows a strong (00 ) preferred orientation, which was confirmed by rocking curve scans that give a ∆θ = 6 • (FWHM) for the (002) peak, due to the highly anisotropic (plate-like) shape of the graphite grains. The sample (∼ 5 × 2.5 × 1.7m...

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supporting

confidence: 84%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Local superconductivity and ferromagnetism interplay in graphite-sulfur composites

Moehlecke¹,

Kopelevich²,

Maple³

2003

Braz. J. Phys.

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Can Carbon Be Ferromagnetic?

Höhne¹,

Esquinazi

2002

Adv. Mater.

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In pure carbon materials, such as fullerenes and highly oriented pyrolytic graphite (HOPG), novel magnetic and electrical properties have recently been discovered. In particular, the discovery of weak ferromagnetism in rhombohedral C60 polymers (Rh‐C60) has attracted the attention of the scientific community and the press. In this paper, the ferromagnetic correlations found in HOPG and Rh‐C60 are commented upon.

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Magnetic Carbon

Esquinazi

2007

Handbook of Magnetism and Advanced Magnetic Materials

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Landau–Lifshitz–Gilbert dynamics is investigated for uniformly magnetized particles subject to constant, pulsed, and circularly polarized applied fields. The Landau–Lifshitz–Gilbert equation is treated as a nonlinear dynamical system on the unit sphere. The equilibria and the phase portraits of this dynamical system, the nature of conservative (precessional) dynamics, and the nature of dissipation are discussed. Conservative Landau–Lifshitz dynamics is studied in detail and analytical expressions are derived for this dynamics in terms of elliptic functions. Then the problem of magnetization switching is studied in detail. Damping and precessional switchings of magnetization in spheroidal particles are discussed for rectangular field pulses, and expressions for critical fields and pulse durations are derived. The phenomenon of ringing, which occurs as the final stage of magnetization switching, is analytically studied using the averaging technique. The final section is devoted to the study of Landau–Lifshitz–Gilbert dynamics in uniformly magnetized particles with rotationally invariant properties, subject to a circularly polarized external field. By using geometric and topological considerations, exact uniform‐mode solutions of the full nonlinear dynamics are obtained for arbitrary values of the excitation conditions. The stability of these solutions is investigated and the conditions leading to periodic or quasiperiodic motions of the magnetization are established. Finally the problem of ferromagnetic resonance is treated using the developed analytical techniques.

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Cited by 261 publications

References 17 publications

Local superconductivity and ferromagnetism interplay in graphite-sulfur composites

Local superconductivity and ferromagnetism interplay in graphite-sulfur composites

Can Carbon Be Ferromagnetic?

Magnetic Carbon

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