Observing thermomagnetic stability of nonideal magnetite particles: Good paleomagnetic recorders?

Trevor P. Almeida, Takeshi Kasama, Adrian R. Muxworthy, Wyn Williams, Lesleis Nagy, Rafal E. Dunin-Borkowski

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    The thermomagnetic behavior of remanence-induced magnetite (Fe3O4) particles in the pseudo-single-domain (PSD) size range (similar to 0.1-10 mu m), which dominate the magnetic signature of many rock lithologies, is investigated using off-axis electron holography. Construction of magnetic induction maps allowed for the visualization of the vortex domain state in an individual Fe3O4 grain (similar to 200nm in diameter) as a function of temperature. Acquisition of a series of electron holograms at 100 degrees C intervals during in situ heating up to 700 degrees C demonstrates the vortex state of the Fe3O4 grain, in this instance, remains thermally stable close to its unblocking temperature and exhibits a similar in-plane remanent state upon cooling; i.e., the particle is effectively behaving like a uniaxial single-domain particle to temperatures near T-C. Such particles are thought to be robust magnetic recorders. It is suggested that evidence for PSD behavior should therefore not preclude paleomagnetic investigation.
    Original languageEnglish
    JournalGeophysical Research Letters
    Issue number20
    Pages (from-to)7041-7047
    Number of pages7
    Publication statusPublished - 2014

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