Structural study of bimetallic CoxRh1-x nanoparticles: Size and composition effects

M. C. Fromen, P. Lecante, M. J. Casanove, G. Bayle Guiliemaud, D. Zitoun, C. Amiens, B. Chaudret, M. Respaud, R. E. Benfield

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

The structure of ultrafine bimetallic CoxRh1-x nanoparticles synthesized in mild conditions by codecomposition of organometallic precursors in the presence of a polymer or a ligand has been studied using high-resolution electron microscopy and wide-angle x-ray scattering techniques. While pure rhodium particles exhibit the main structural features of a face centered cubic (fcc), alloying with cobalt induces a progressive loss of periodicities, leading in high-cobalt-content particles to a polytetrahedral structure close to the one already encountered in pure-cobalt particles. When increasing the synthesis temperature, the polytetrahedral structure remains remarkably stable, while particles with higher rhodium content clearly evolve towards perfect fcc. Increasing the size of the particles up to 5-6 nm stabilizes the structural phases encountered in the phase diagram of the bulk alloy. Different element-sensitive techniques, x-ray absorption spectroscopy (XANES and EXAFS) and energy-filtering transmission electron microscopy, have also been implemented in order to get chemical information. Evidence is given for a cobalt surface segregation in these bimetallic particles, highly favorable for magnetic-moment enhancement.

Original languageEnglish
Article number235416
Pages (from-to)235416-1-235416-9
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume69
Issue number23
DOIs
StatePublished - Jun 2004
Externally publishedYes

Bibliographical note

Funding Information:
The authors acknowledge the European Synchrotron Radiation Facility for provision of synchrotron radiation facilities and we would like to thank Dr. V. Honkimaki for assistance in using beamline ID15B. They also acknowledge financial support through the IHP-Contract No. HPRI-CT-1999-00040∕2001-00140 of the European Commission for the measurements on beamline at Hasylab, and the assistance of Dr. P. Kappen and Dr. J. Wienold in using this beamline.

Funding

The authors acknowledge the European Synchrotron Radiation Facility for provision of synchrotron radiation facilities and we would like to thank Dr. V. Honkimaki for assistance in using beamline ID15B. They also acknowledge financial support through the IHP-Contract No. HPRI-CT-1999-00040∕2001-00140 of the European Commission for the measurements on beamline at Hasylab, and the assistance of Dr. P. Kappen and Dr. J. Wienold in using this beamline.

FundersFunder number
European Commission

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