X-ray magnetic circular dichrosm provides strong evidence for tetrahedral iron in ferrihydrite

Yohan Guyodo, Philippe Sainctavit, Marie Anne Arrio, Claire Carvallo, R. Lee Penn, Jasmine J. Erbs, Brady S. Forsberg, Guillaume Morin, Fabien Maillot, France Lagroix, Pierre Bonville, Fabrice Wilhelm, Andrei Rogalev

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31 Scopus citations

Abstract

Ferrihydrite is an important iron oxyhydroxide for earth and environmental sciences, biology, and technology. Nevertheless, its mineral structure remains a matter of debate. The stumbling block is whether a significant amount of tetrahedrally coordinated iron is present. Here we present the first X-ray magnetic circular dichrosm (XMCD) measurements performed on a well characterized synthetic sample of 6-line ferrihydrite, at both K and L2,3 energy edges of iron. XMCD results demonstrate unambiguously the presence of tetrahedrally coordinated Fe(III) in the mineral structure, in quantities compatible with the latest extended X-ray absorption fine structure (EXAFS) analyses suggesting a concentration of 20-30%. Moreover, we find an antiferromagnetic coupling between tetrahedral and octahedral sublattices, with the octahedral sublattice parallel to the external magnetic field.

Original languageEnglish (US)
Article numberQ06Z44
JournalGeochemistry, Geophysics, Geosystems
Volume13
Issue number6
DOIs
StatePublished - Jun 1 2012

Keywords

  • XMCD
  • ferrihydrite
  • magnetic properties

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