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Structural and Magnetic Properties of Ferrihydrite

Published online by Cambridge University Press:  28 February 2024

Q. A. Pankhurst
Affiliation:
Department of Physics, University of Liverpool, Liverpool L69 3BX, England
R. J. Pollard
Affiliation:
Department of Physics, University of Liverpool, Liverpool L69 3BX, England Department of Physics, Monash University, Clayton, Victoria 3168, Australia
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Abstract

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57Fe Mössbauer spectra of two synthetic samples of ferrihydrite, recorded at 4.2 K in applied fields of up to 9 T, have been analysed by a mean-field model. The samples exhibit two and six X-ray diffraction peaks. It is shown that only one ferric ion site is present in the mineral, and that in this site the ions are octahedrally coordinated. The spectra show the presence of different magnetic states: ferrimagnetism in two-line ferrihydrite, and antiferromagnetism in six-line ferrihydrite. The ferrimagnetism in two-line ferrihydrite is analysed in terms of random fluctuations arising from the small numbers of ferric ions per particle, and it is shown that the different magnetic states may arise purely as a result of these fluctuations.

Type
Research Article
Copyright
Copyright © 1992, The Clay Minerals Society

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