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158 results on '"Pascard, H."'

2. Magnetization reversal by uniform rotation (Stoner-Wohlfarth model) in f.c.c. cobalt nanoparticles

Author

Wernsdorfer, W., Thirion, C., Demoncy, N., Pascard, H., and Mailly, D.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

The combination of high sensitive superconducting quantum interference device (SQUID) with high quality nanoparticles allowed to check the simplest classical model describing the magnetisation reversal by uniform rotation which were proposed more than 50 years ago by Neel, Stoner and Wohlfarth. The micrometer sized SQUIDs were elaborated by electron beam lithography and the nanoparticles were synthesised by arc-discharge. The measured angular dependence of switching fields of nearly all f.c.c. Co nanoparticles revealed a dominating uniaxial magnetic anisotropy. This result suggests that twin boundaries and stacking faults strongly alter the cubic magnetocrystalline anisotropy leading to dominating uniaxial anisotropy. However, few particles were sufficiently "perfect" in order to show a more complex switching field surface and a field path dependence of the switching field which is the important signature of the cubic magnetocrystalline anisotropy., Comment: 9 pages, 10 figures; conference proceeding: 1st Joint European Magnetic Symposia (JEMS'01), Grenoble (France), 28th August - 1st September, 2001

Published
2001
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10. Magnetization reversal in individual nanoparticles - macroscopic quantum tunneling of magnetization

Author

Wernsdorfer, W., Orozco, E. Bonet, Barbara, B., Benoit, A., Mailly, D., Demoncy, N., Pascard, H., Kubo, O., and Nakano, H.

Subjects
Superconducting quantum interference devices -- Usage, Magnetization -- Research, Tunneling (Physics) -- Analysis, Business, Electronics, Electronics and electrical industries
Abstract

The combination of highly sensitive Superconducting Quantum Interference Device (SQUID) with high quality nanoparticles allowed us to check for the first time simple classical models proposed nearly 50 years ago by Neel, Stoner and Wohlfarth. For nanoparticles containing about [10.sup.5] to [10.sup.6] [[Mu].sub.B] the quantitative agreement with the Neel-Brown theory of thermal activated magnetization reversal allowed us to identify unambiguously the magnetization reversal mechanism as uniform rotation. In the case of insulating barium ferrite nanoparticles containing about [10.sup.5] [[Mu].sub.B] and below 0.4 K, strong deviations from this model are found which are quantitatively in agreement with the predictions of the theory of macroscopic quantum tunneling of magnetization in the low dissipation regime. Index Terms - Single domain nanoparticles, magnetization reversal in unison, Neel - Brown theory, macroscopic quantum tunneling of magnetization.

Published
1998

11. Relation between metal electronic structure and morphology of metal compounds inside carbon nanotubes

Author

Guerret-Piecourt, C., Bouar, Y. Le, Loiseau, A., and Pascard, H.

Subjects
Nanotechnology -- Research, Metals -- Analysis, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

An arc-discharge technique of filling carbon nanotubes with metals and their compounds helps determine the materials appropriate to yield distinct nanocomposite materials upon filling carbon nanotubes. The presence of an incomplete electronic shell in the most stable ionic state of the metal increases the susceptibility for the formation of continuous nanowires throughout the tubes. Interactions between growth of the nanotube and that of the filling contributes to the formation of a distinct helical filling morphology.

Published
1994

14. Ferromagnetic resonance damping in garnets: comparison between saturated and unsaturated states

Author

Taffary, T., Autissier, D., Boust, F., and Pascard, H.

Subjects
Damping (Mechanics) -- Research, Garnet -- Research, Magnetism -- Research, Business, Electronics, Electronics and electrical industries
Abstract

The influence of magnetic state (saturated or unsaturated states) on the ferromagnetic resonance damping in relaxing rare earth substituted [Y.sub.1-x]R[E.sub.x][Gd.sub.2][Fe.sub.5][O.sub.12] garnets (with RE = Dy Ho, Tb and x = 0;0.15;0.3;0.6) has been studied. The damping parameter [Alpha], as defined by Landau-Lifshitz equation, has been determined either by FMR at 10GHz ([[Alpha].sub.sat] for saturated state) or by measurement of the frequency dependence of the complex initial permeability in the 0.1GHz-10GHz band ([[Alpha].sub.unsat] for unsaturated state). in the saturated state the introduction of relaxing rare earth is found to increase significantly [[Alpha].sub.sat] values by more than one order of magnitude. On the contrary, although [[Alpha].sub.unsat] values also increase with rare earth concentration they stay in the same order of magnitude. It appears that [[Alpha].sub.unsat] is controlled either by the magnetic disorder introduced via the domain and domain wall structure or by the rare earth concentration. Index Terms - damping, gyromagnetism, garnets

Published
1998

15. Mesoscopic effects in magnetism: submicron to nanometer size single particle measurements

Author

Wernsdorfer, W., Orozco, E. Bonet, Barbara, B., Hasselbach, K., Benoit, A., Mailly, D., Doudin, B., Meier, J., Wegrowe, J.E., Ansermet, J.-Ph., Demoncy, N., Pascard, H., Loiseau, A., Francois, L., Duxin, N., and Pileni, M.P.

Subjects
Thin films -- Magnetic properties, Magnetization -- Measurement, Ferromagnetism -- Analysis, Crystals -- Magnetic properties, Domain structure -- Analysis, Ferromagnetic materials -- Analysis, Physics
Published
1997

23. Tracks in YIG induced by MeV C$_{60}$ ions

Author

Jensen, J., Dunlop, A., Della Negra, S., Pascard, H., Institut de Physique Nucléaire d'Orsay (IPNO), and Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract

NIM

Published
1998

30. Boron nitride nanotubes

Author

Loiseau, A., primary, Willaime, F., additional, Demoncy, N., additional, Schramchenko, N., additional, Hug, G., additional, Colliex, C., additional, and Pascard, H., additional

Published
1998
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