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(59)Co NMR study of the allotropic phase transformation in small ferromagnetic cobalt particles

Speight, R. J. (Richard J.) and Wong, A. and Ellis, P. and Bishop, P. T. and Hyde, T. I. and Bastow, T. J. and Smith, Mark E. (2009) (59)Co NMR study of the allotropic phase transformation in small ferromagnetic cobalt particles. Physical Review B, 79 (5). ISSN 1098-0121

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    Abstract

    To demonstrate the potential of nuclear-magnetic-resonance (NMR) spectroscopy in investigating detailed structural properties in ferromagnetic materials, the allotropic phase transformation of polycrystalline cobalt with mu m particle size (<2 mu m) is characterized by internal-field Co-59 NMR. The Co-59 NMR spectra show distinct resonance bands corresponding to the different Co sites: face-centered cubic (fcc), hexagonal-close packed (hcp), and stacking faults (sfs), in Co metal powder. The hcp -> fcc phase-transition temperature is determined by systematically monitoring the signal intensity of each Co environment in a series of heat-treated Co powders. The potential limits to which absolute quantification of the different sites can be pushed are mentioned, with relative changes in intensity giving unequivocal evidence of the structural evolution. For example, the phase-transition temperature is observed to be 500 +/- 25 degrees C, and above this temperature, the sf Co sites were reduced by more than 10%.

    Item Type: Article
    Journal or Publication Title: Physical Review B
    Additional Information: © 2009 The American Physical Society
    Uncontrolled Keywords: cobalt, ferromagnetic materials, magnetic transitions, NMR spectroscopy, stacking faults
    Subjects: UNSPECIFIED
    Departments: VC's Office
    ID Code: 52834
    Deposited By: ep_importer_pure
    Deposited On: 28 Feb 2012 13:43
    Refereed?: Yes
    Published?: Published
    Last Modified: 17 Sep 2013 08:31
    Identification Number:
    URI: http://eprints.lancs.ac.uk/id/eprint/52834

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