Open AccessMagnetic anisotropy and Verwey transition of magnetosome chains in Magnetospirillum gryphiswaldense
Author(s) -
Gehring Andreas U.,
Fischer Håkon,
Charilaou Michalis,
GarcíaRubio Inés
Publication year - 2011
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2011.05175.x
Subject(s) - magnetosome , magnetocrystalline anisotropy , condensed matter physics , magnetotactic bacteria , anisotropy , materials science , magnetic anisotropy , ferromagnetic resonance , magnetization , magnetite , nuclear magnetic resonance , magnetic field , physics , optics , quantum mechanics , metallurgy
SUMMARY Magnetotactic bacteria (MTB) are characterized by cellular magnetic dipoles formed by the 1‐D assembly of magnetite and/or greigite particles aligned along their magnetic easy axes. This alignment creates strong interaction‐induced shape anisotropy. Ferromagnetic resonance (FMR) spectroscopy is applied to study the changes in anisotropy of the MTB Magnetospirillum gryphiswaldense between room temperature and 10 K. The Verwey transition is found at about 100 K. The characteristic FMR signal of the cellular dipole at room temperature vanishes upon cooling to the isotropic point at T i ≈ 130 K, where the magnetocrystalline anisotropy constant K 1 becomes zero. Monitoring of the FMR response of intact MTB as a function of temperature is taken to discuss theoretically the reduction of the interaction‐induced shape anisotropy in magnetofossils because of diagenetic processes. It is concluded that there is a similarity in the FMR response between magnetofossils at room temperature and intact MTB near T i . This is because the critical effect of the magnetocrystalline anisotropy constant K 1 and of the alignment of magnetic easy axes on the cellular dipole. Low‐temperature FMR results of intact MTB can thus be used as a guideline for detecting magnetofossils in geological environments.