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Probing the site occupancies of Co-, Ni-, and Mn-substituted biogenic magnetite using XAS and XMCD

Victoria S. Coker, Carolyn I. Pearce, Richard A. D. Pattrick, Gerrit van der Laan, Neil D. Telling, John M. Charnock, Elke Arenholz and Jonathan R. Lloyd
Probing the site occupancies of Co-, Ni-, and Mn-substituted biogenic magnetite using XAS and XMCD
American Mineralogist (July 2008) 93 (7): 1119-1132


Ferrimagnetic nanoparticles have many uses in industry including in magnetic recording media and transformers, however these particles are often expensive to synthesize. In this study, the Fe (super 3+) -reducing bacteria Geobacter sulfurreducens and Shewanella oneidensis were used to synthesize spinel ferrite nanoparticles of the general chemical formula M (sub x) Fe (sub 3-x) O (sub 4) , where M is either Co, Ni, Mn, Zn, or a combination of Mn and Zn. This was done at ambient temperatures through the dissimilatory reduction of Fe (super 3+) -oxyhydroxides containing the appropriate substitutional cations. A combination of L-edge and K-edge X-ray absorption spectroscopy (XAS) and L-edge X-ray magnetic circular dichroism (XMCD) was used to determine the site occupancies, valence, and local structure of the Fe and substitutional cations within the spinels. The Ni and Co ferrites produced using each bacterium were very similar and therefore this study concludes that, despite the difference in reduction mechanism of the bacteria used, the end-product is remarkably unaltered. Nickel ferrites contained only Ni (super 2+) , with at least 80% in O (sub h) coordination. Cobalt ferrites contained only Co (super 2+) but with a significant proportion (up to 45%) in T (sub d) coordination, showing a slight preference for T (sub d) sites. The Mn-ferrites contained Mn (super 2+) only on the O (sub h) sites but a mixture of Mn (super 2+) and Mn (super 3+) on T (sub d) sites when the amount of Mn exceeded 3% (compared to the amount of Fe) or some Zn was also present. This study successfully produced a range of nanoparticulate ferrites that could be produced industrially using relatively environmentally benign methodologies.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 93
Serial Issue: 7
Title: Probing the site occupancies of Co-, Ni-, and Mn-substituted biogenic magnetite using XAS and XMCD
Affiliation: University of Manchester, School of Earth, Atmospheric and Environmental Sciences, Manchester, United Kingdom
Pages: 1119-1132
Published: 200807
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 46
Accession Number: 2008-104144
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
Secondary Affiliation: Daresbury Laboratory, GBR, United KingdomDiamond Light Source, GBR, United KingdomLawrence Berkeley National Laboratory, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200836
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