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Hamid KACHKACHI


Maître de Conférences - Associate Professor

Habilité à Diriger des Recherches

Moving to the University of Perpignan (September 1, 2008)
as Full Professor (CNU 28)

Groupe d'Etude de la Matière Condensée
Université de Versailles Saint Quentin

Bât. Fermat, 45 avenue des Etats-Unis
78035 Versailles cedex, France
33/0 1 39 25 46 93,
33/0 1 39 25 46 52,
Hamid Kachkachi
"I have so often been through these periods of strain that I have become accustomed to the fact that most of the calamities that we anticipate really never occur"
D.D. Eisenhauer

"Créer - voilà la grande délivrance de la souffrance, voilà ce qui rend la vie légère. Mais pour qu'existe celui qui crée il faut beaucoup de souffrance et de métamorphose"
F. Nietzsche

THEORETICAL PHYSICS
Magnetism of Nano-scale Systems

Quantum field theory, statistical physics, critical phenomena, and applications to magnetism and nanomagnetism

"The task is not so much to see what nobody has seen yet, but to think what nobody has thought yet about what everybody sees", A. Schopenhauer

Magnetic properties of small magnetic systems



(articles accessible at http://arxiv.org/cond-mat )

    Small magnetic particles have been of much interest owing to their technological applications, mainly in the area of information storage. From the experimental and theoretical point of view, these systems are very interesting for they show superparamagnetism at high temperature and exponentially slow relaxation rates at low temperature due to anisotropy barriers. Although in most of theoretical approaches to the dynamics of a small magnetic particle the latter is considered as a single magnetic moment, deviations from this simple picture become crucial with the reduction of the system size. In magnetic nanoparticles, the contribution of the surface to the thermodynamic properties becomes comparable with the bulk contribution, and the magnetisation and other characteristics may become spatially inhomogeneous.

    The latter situation is realised due to additional thermal disordering near the surface at elevated temperatures or due to the breaking of symmetry of the crystal field for surface spins, which results in a strong surface anisotropy. Another manifestation of the symmetry breaking at the surface is the possible unquenching of the orbital moments of surface spins, which may be responsible for a significant increase of the particle's magnetic moment, e.g. in 3d (transition) elements.

" There's Plenty of Room at the Bottom", R.P. Feynman