Structure and chemical order in nanoparticles

Centre d'Élaboration de Matériaux et d'Études Structurales, CNRS 29 Rue Jeanne Marvig, 31055 Toulouse Cedex 4, France

Received: 29 June 2005
Accepted: 16 January 2006

Abstract

The structure of soft chemistry synthesized (, 0.50, 0.75) particles, 1.7 to large, has been determined by atomic-scale simulations using an interaction model fitted on both ab initio and experimental results. All the measured structural features, strongly different from the ones in the corresponding bulk alloys, have been consistently reproduced. Two major effects, i.e. a strong Co surface segregation and an expansion of the mean bond length, are demonstrated and both are consistent with the drastic enhancement of the magnetization observed in these clusters. Interestingly, the method also provides new insights into interpretation of the experimental results.