Structure and magnetism of Co:CoO core-shell nanoclusters

X. Z. Li, X. H. Wei, R. Skomski, D. J. Sellmyer

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
Pages (from-to)789-794
Number of pages6
JournalJournal of Nanoparticle Research
Volume12
Issue number3
DOIs
StatePublished - Mar 1 2010

Fingerprint

Nanoclusters
Magnetism
nanoclusters
Shell
Salts
Rocks
Shell Structure
Transmission electron microscopy
Electron diffraction
Transmission Electron Microscopy
Salt
halites
Granular materials
Exchange interactions
Magnetic variables measurement
Diffraction
Hysteresis loops
Nanostructures
Electron
Magnetic properties

Keywords

  • Core-shell nanoclusters
  • Electron diffraction
  • Electron microscopy
  • Magnetic nanostructures
  • Nanoparticles

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Atomic and Molecular Physics, and Optics
  • Modeling and Simulation
  • Materials Science(all)
  • Condensed Matter Physics

Cite this

Structure and magnetism of Co:CoO core-shell nanoclusters. / Li, X. Z.; Wei, X. H.; Skomski, R.; Sellmyer, D. J.

In: Journal of Nanoparticle Research, Vol. 12, No. 3, 01.03.2010, p. 789-794.

Research output: Contribution to journalArticle

Li, X. Z. ; Wei, X. H. ; Skomski, R. ; Sellmyer, D. J. / Structure and magnetism of Co:CoO core-shell nanoclusters. In: Journal of Nanoparticle Research. 2010 ; Vol. 12, No. 3. pp. 789-794.
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