Détail de la notice
Titre du Document
Structure and magnetism of Co:CoO core-shell nanoclusters
Auteur(s)
Li X. Z. ; Wei X. H. ; Skomski R. ; ...
Résumé
Transmission electron microscopy (TEM) and electron diffraction (ED) are used to investigate the nanostructures of two ensembles of Co:CoO core-shell particles. TEM images show that particles of size about 12 nm are almost fully oxidized, while particles with size about 18 nm have a core-shell structure where a Co core is surrounded by a shell of CoO. ED simulation confirms that the larger particles have an fcc-structured Co core and a rock-salt CoO shell structure, while the smaller particles mostly have the rock-salt CoO structure. The core-shell structure is responsible for the unusual magnetic properties of the Co:CoO nanoclusters, especially the occurrence of inverted hysteresis loops (proteresis), but previous research has been indirect, largely based on magnetic measurements and on a cross-comparison with granular materials. Our measurements show that the structures have ferromagnetic fcc Co cores of varying sizes down to 1 nm which are surrounded by antiferromagnetic rock-salt CoO shells. The core radii obtained from the TEM pictures are used to estimate the exchange interactions responsible for proteresis and to pinpoint the core-size window in which proteresis occurs.
Editeur
Springer
Identifiant
ISSN : 1572-896X
Source
Journal of nanoparticle research (Dordrecht. Online) A. 2010, vol. 12, n° 3, pp. 789-794 [6 pages]
Langue
Anglais
Copyright
Springer Science+Business Media B.V., 2010
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