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GEOREF RECORD

Off-axis electron holography of magnetotactic bacteria; magnetic microstructure of strains MV-1 and MS-1

Rafal E. Dunin-Borowski, Martha R. McCartney, Mihaly Posfai, Richard B. Frankel, Dennis A. Bazylinski and Peter R. Buseck
Off-axis electron holography of magnetotactic bacteria; magnetic microstructure of strains MV-1 and MS-1 (in Biogenic iron minerals, Mihaly Posfai (prefacer))
European Journal of Mineralogy (August 2001) 13 (4): 671-684

Abstract

Off-axis electron holography in the transmission electron microscope is used to characterize the magnetic microstructure of magnetotactic bacteria. The practical details of the technique are illustrated through the examination of single cells of strains MV-1 and MS-1, which contain crystals of magnetite (Fe (sub 3) O (sub 4) ) that are approximately 50 nm in size and are arranged in chains. Electron holography allows the magnetic domain structures within the nanocrystals to be visualized directly at close to the nanometer scale. The crystals are shown to be single magnetic domains. The magnetization directions of small crystals that would be superparamagnetic if they were isolated are found to be constrained by magnetic interactions with adjacent, larger crystals in the chains. Magnetization reversal processes are followed in situ, allowing a coercive field of between 30 and 45 mT to be measured for the MV-1 cell. To within experimental error, the remanent magnetizations of the chains are found to be equal to the saturation magnetization of magnetite (0.60T). A new approach is used to determine that the magnetic moments of the chains are 7 and 5X10 (super -16) Am (super 2) for the 1600-nm long MV-1 and 1200-nm long MS-1 chains examined, respectively. The degree to which the observed magnetic domain structure is reproducible between successive measurements is also addressed.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 13
Serial Issue: 4
Title: Off-axis electron holography of magnetotactic bacteria; magnetic microstructure of strains MV-1 and MS-1
Title: Biogenic iron minerals
Affiliation: University of Cambridge, Department of Minerals Science and Metallurgy, Cambridge, United Kingdom
Affiliation: University of Veszprem, Hungary
Pages: 671-684
Published: 200108
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
Meeting name: Biogenic iron minerals symposium and workshop
Meeting location: Tihany, HUN, Hungary
Meeting date: 20000520May 20-23, 2000
References: 40
Accession Number: 2001-065621
Categories: Mineralogy of non-silicates
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus.
Secondary Affiliation: Arizona State University, USA, United StatesUniversity of Veszprem, HUN, HungaryCalifornia Polytechnic State University, USA, United StatesIowa State University, USA, United States
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute.
Update Code: 200120
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