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Structural, morphological, and magnetic study of nanocrystalline cobalt-copper powders synthesized by the polyol process

Published online by Cambridge University Press:  03 March 2011

G.M. Chow*
Affiliation:
Laboratory for Molecular Interfacial Interactions, Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC 20375
L.K. Kurihara
Affiliation:
Laboratory for Molecular Interfacial Interactions, Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC 20375
K.M. Kemner
Affiliation:
Condensed Matter and Radiation Division, Naval Research Laboratory, Washington, DC 20375
P.E. Schoen
Affiliation:
Laboratory for Molecular Interfacial Interactions, Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC 20375
W.T. Elam
Affiliation:
Condensed Matter and Radiation Division, Naval Research Laboratory, Washington, DC 20375
A. Ervin
Affiliation:
Chemistry Division, Naval Research Laboratory, Washington, DC 20375
S. Keller
Affiliation:
Department of Physics, University of Connecticut, Storrs, Connecticut 06269
Y.D. Zhang
Affiliation:
Department of Physics, University of Connecticut, Storrs, Connecticut 06269
J. Budnick
Affiliation:
Department of Physics, University of Connecticut, Storrs, Connecticut 06269
T. Ambrose
Affiliation:
Department of Physics, Johns Hopkins University, Baltimore, Maryland 21218
*
a)Author to whom correspondence should be addressed.
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Abstract

Nanocrystalline CoxCu100−x (4 ⋚ x ⋚ 49 at. %) powders were prepared by the reduction of metal acetates in a polyol. The structure of powders was characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), extended x-ray absorption fine structure (EXAFS) spectroscopy, solid-state nuclear magnetic resonance (NMR) spectroscopy, and vibrating sample magnetometry (VSM). As-synthesized powders were composites consisting of nanoscale crystallites of face-centered cubic (fcc) Cu and metastable face-centered cubic (fcc) Co. Complementary results of XRD, HRTEM, EXAFS, NMR, and VSM confirmed that there was no metastable alloying between Co and Cu. The NMR data also revealed that there was some hexagonal-closed-packed (hcp) Co in the samples. The powders were agglomerated, and consisted of aggregates of nanoscale crystallites of Co and Cu. Upon annealing, the powders with low Co contents showed an increase in both saturation magnetization and coercivity with increasing temperature. The results suggested that during preparation the nucleation of Cu occurred first, and the Cu crystallites served as nuclei for the formation of Co.

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Articles
Copyright
Copyright © Materials Research Society 1995

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References

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