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Phys. Rev. B 74, 184413 (2006) [8 pages]

Tunable magnetic properties of metal/metal oxide nanoscale coaxial cables

Olga Kazakova,1 Brian Daly,2 and Justin D. Holmes2
1National Physical Laboratory, Teddington, United Kingdom
2Materials Section and Supercritical Fluid Centre, Department of Chemistry, University College Cork, Cork, Ireland

Received 16 June 2006; revised 20 September 2006; published 8 November 2006

We report the synthesis and magnetic characterization of metal/metal oxide one-dimensional heterostructures with a radial geometry—coaxial nanocables. High-density arrays of cobalt and magnetite- (Fe3O4) based nanocables with the diameter of ~100  nm and length of ~60  µm have been synthesized within the pores of anodized aluminum oxide membranes using a supercritical fluid inclusion-phase technique. All investigated heterostructures demonstrate ferrimagnetic/ferromagnetic properties at room temperature. We show that the magnetic properties of cobalt-magnetite nanocables can be tuned by varying the thickness of the sheath and core layers. The exchange bias effect, due to formation of CoO thin layers at the nanocable interfaces, was observed at low temperatures. The strength and manifestation of this effect depends on the structural characteristics and oxidation state of the Co layer. We show that the vast increase of the coercive field (up to 450 times) at low temperatures in samples containing the large fraction of magnetite is caused by a governing influence of the temperature-dependent magnetoelastic term of the anisotropy.

©2006 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevB.74.184413
DOI: 10.1103/PhysRevB.74.184413
PACS: 75.30.Gw; 75.70.Cn; 75.75.+a
  • 75.30.Gw
    Magnetic anisotropy
  • 75.70.Cn
    Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
  • 75.75.+a
    Magnetic properties of nanostructures
  • YEAR: 2006
KEYWORDS: iron compounds, cobalt, ferromagnetic materials, ferrimagnetic materials, coaxial cables, exchange interactions (electron), oxidation, coercive force, magnetoelastic effects, magnetic anisotropy

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