TY - JOUR
T1 - Off-axis electron holography of magnetotactic bacteria
T2 - Magnetic microstructure of strains MV-1 and MS-1
AU - Dunin-Borkowski, R. E.
AU - McCartney, Martha
AU - Pósfai, M.
AU - Frankel, R. B.
AU - Bazylinski, D. A.
AU - Buseck, P. R.
PY - 2001
Y1 - 2001
N2 - 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 (Fe3O4) that are ∼ 50nm 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 5x10-16Am2 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.
AB - 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 (Fe3O4) that are ∼ 50nm 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 5x10-16Am2 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.
KW - Biologically controlled mineralization
KW - Magnetite nanocrystals
KW - Magnetotactic bacteria
KW - Off-axis electron holography
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U2 - 10.1127/0935-1221/2001/0013-0671
DO - 10.1127/0935-1221/2001/0013-0671
M3 - Article
AN - SCOPUS:0034916448
SN - 0935-1221
VL - 13
SP - 671
EP - 684
JO - European Journal of Mineralogy
JF - European Journal of Mineralogy
IS - 4
ER -