Contribution à l'étude des propriétés de matériaux magnétiques nanostructurés

This manuscript is presenting a years work on soft magnetic materials. Starting from some general considerations on the influence of size on physical systems, will propose a new classification of nanostructured material and its relevence in magntism. In a second step, a critical review of random anisotropy done with intention to show the relevence of shape anisotropy in Finemet type systems. A study of phase transition in FeCo based nanocrystallne materials is presented with emphasis on the role of cristalline fraction. In a third step, properties of soft magnetic composites processed from powder are presented, followed by a discussion on the magnetic structure of nanoparticles based on electron holography experiments. Finally, prospective of this work is presented.