Issue
Europhys. Lett.
Volume 73, Number 6, March 2006
Page(s) 885 - 891
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
DOI http://dx.doi.org/10.1209/epl/i2005-10469-3
Published online 01 February 2006
Europhys. Lett., 73 (6), pp. 885-891 (2006)
DOI: 10.1209/epl/i2005-10469-3

Structure and chemical order in $\chem{Co\tx{-}Rh}$ nanoparticles

M. C. Fromen, J. Morillo, M. J. Casanove and P. Lecante

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


received 29 June 2005; accepted in final form 16 January 2006
published online 1 February 2006

Abstract
The $300\un{K}$ structure of soft chemistry synthesized $\chem{Co_{\it x} Rh_{1-{\it x}}}$ (x = 0.25, 0.50, 0.75) particles, 1.7 to $2.5\un{nm}$ 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.

PACS
61.46.Df - Nanoparticles.
61.10.Eq - X-ray scattering (including small-angle scattering).
61.43.Bn - Structural modeling: serial-addition models, computer simulation.

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