Etude expérimentale et modélisation de la structure de nanoparticules magnétiques : des particules isolées aux assemblages

Abstract : The combination of size and alloying effects in bimetallic nanoparticles is known to enhance their properties or even generate new ones. The present study was motivated by the occurrence of such effects in nanometric size particles of cobalt-rhodium alloy. More precisely, it is dedicated to the analysis of their fine structure and its evolution with composition and synthesis conditions, likely to explain their magnetic properties. The experimental study was carried out using a large combination of techniques, the major contribution being given by high-resolution electron microscopy and wide angle X-ray scattering. Evidence has thus been given for a sudden increase of the mean metal-metal bond length as soon as some rhodium is present in the particle. This particular behaviour, combined with different results obtained by element selective techniques like EXAFS, suggests the presence of some cobalt segregation at the surface. The theoretical study is based on a semi-empirical N-body potential. Monte Carlo Metropolis calculations confirm the main structural results and above all the strong tendency for cobalt to segregate at the particle surface. Finally, in the last part of this work, we focus on the structural study of cobalt-alloys particles, with controlled morphology and assembling, dedicated to microelectronics.
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Contributor : Marie-Claire Fromen <>
Submitted on : Tuesday, November 4, 2003 - 4:27:20 PM
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Marie-Claire Fromen. Etude expérimentale et modélisation de la structure de nanoparticules magnétiques : des particules isolées aux assemblages. Physique [physics]. INSA de Toulouse, 2003. Français. ⟨tel-00003695⟩

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