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Conference paperMuxworthy AR, 2015,
How well does Preisach Theory predict Pseudo-Single-Domain Behavior? (poster)
, AGU Fall 2015 -
Conference paperAbubakar R, Muxworthy AR, Sephton M, et al., 2015,
Mapping Petroluem Migration Pathways Using Magnetics and Seismic Interpretations (poster)
, AGU Fall 2015 -
Journal articleMuxworthy AR, 2015,
Investigation of magnetic particulate matter inside animals' lung tissue: preliminary results
, STUDIA GEOPHYSICA ET GEODAETICA, Vol: 59, Pages: 628-634, ISSN: 0039-3169- Author Web Link
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- Citations: 2
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Journal articleAlmeida TP, Muxworthy AR, Kasama T, et al., 2015,
Effect of maghemization on the magnetic properties of nonstoichiometric pseudo-single-domain magnetite particles
, Geochemistry Geophysics Geosystems, Vol: 16, Pages: 2969-2979, ISSN: 1525-2027The effect of maghemization on the magnetic properties of magnetite (Fe3O4) grains in the pseudo-single-domain (PSD) size range is investigated as a function of annealing temperature. X-ray diffraction and transmission electron microscopy confirms the precursor grains as Fe3O4 ranging from ~ 150 nm to ~ 250 nm in diameter, whilst Mössbauer spectrometry suggests the grains are initially near-stoichiometric. The Fe3O4 grains are heated to increasing reaction temperatures of 120 – 220 ºC to investigate their oxidation to maghemite (γ-Fe2O3). High-angle annular dark field imaging and localized electron energy loss spectroscopy reveals slightly oxidized Fe3O4 grains, heated to 140 ºC, exhibit higher oxygen content at the surface. Off-axis electron holography allows for construction of magnetic induction maps of individual Fe3O4 and γ-Fe2O3 grains, revealing their PSD (vortex) nature, which is supported by magnetic hysteresis measurements, including first order reversal curve analysis. The coercivity of the grains is shown to increase with reaction temperature up to 180 ºC, but subsequently decreases after heating above 200 ºC; this magnetic behavior is attributed to the growth of a γ-Fe2O3 shell with magnetic properties distinct from the Fe3O4 core. It is suggested there is exchange coupling between these separate components that results in a vortex state with reduced vorticity. Once fully oxidized to γ-Fe2O3, the domain states revert back to vortices with slightly reduced coercivity. It is argued that due to a core/shell coupling mechanism during maghemization, the directional magnetic information will still be correct, however, the intensity information will not be retained.
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Conference paperShah J, Muxworthy AR, Russell SS, et al., 2015,
USING MICRO-CT TO MAP METEORITIC MAGNETISM.
, 78th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, ISSN: 1086-9379 -
Conference paperShah J, Muxworthy AR, Almeida TP, et al., 2015,
VISUALIZING THE MAGNETIC BEHAVIOR OF CHONDRULE DUSTY OLIVINE USING ELECTRON HOLOGRAPHY.
, 78th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, ISSN: 1086-9379 -
Conference paperMuxworthy AR, Bland PA, Collins G, et al., 2015,
MAGNETIC FABRICS IN ALLENDE: IMPLICATIONS FOR MAGNETIC REMANENCE ACQUISITION.
, 78th Annual Meeting of the Meteoritical-Society, Publisher: WILEY, ISSN: 1086-9379 -
Conference paperDi Chiara A, Muxworthy AR, Trindade R, 2015,
Palaeointensity of Proterozoic magmatic rocks from South America using the Preisach method, preliminary results
, IUGG 2015 -
Conference paperBerndt T, Muxworthy AR, Paterson G, et al., 2015,
Temperature and grain size dependence of the attempt time t0 for fine magnetic particles
, IUGG 2015 -
Conference paperBerndt T, Muxworthy AR, 2015,
Viscous remanent magnetization dating of cataclysmic floods in Iceland
, IUGG 2015 -
Journal articleMuxworthy AR, Williams W, 2015,
Critical single-domain grain sizes in elongated iron particles: implications for meteoritic and lunar magnetism
, Geophysical Journal International, Vol: 202, Pages: 578-583, ISSN: 1365-246XKamacite particles (Fe–Ni, Ni < 5 per cent), are very common in extra-terrestrial materials, such as meteorites. It is normally assumed that for kamacite particles to be reliable recorders of magnetic fields, they need to be magnetically uniform (single domain, SD) and thermally stable. Larger particles subdivide into non-uniform multidomain (MD) magnetic structures that produce weaker magnetic signals, while small SD particles become magnetically unstable due to thermal fluctuations and exhibit superparamagnetic behaviour. In this paper we determine the first micromagnetic calculation of the stable SD range domain-state phase diagram for metallic iron; previous calculations were analytical. There is a significant increase in the critical size for the SD/MD threshold size, for example, for cube-shaped iron particles, the critical SD/MD threshold has now been estimated to be 25 nm, compared to 17 nm for previous estimates. The larger critical SD/MD threshold size for iron, agrees better with previously published nanometric observations of domain state for FeNi particles, then early analytical models.
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Conference paperDøssing A, Muxworthy AR, Mac Niocaill C, et al., 2015,
Geomagnetic secular variation during 6-0.5 Ma: Paleomagnetic results from Eastern Iceland
, IUGG 2015 -
Conference paperMuxworthy AR, Heslop D, 2015,
Recovering Ancient Magnetic Field Intensities From Rocks Using FORC Measurements (poster)
, HMM2015 -
Journal articleDodd SC, Mac Niocaill C, Muxworthy AR, 2015,
Long duration (>4 Ma) and steady-state volcanic activity in the early Cretaceous Parana-Etendeka Large Igneous Province: New palaeomagnetic data from Namibia
, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 414, Pages: 16-29, ISSN: 0012-821X- Author Web Link
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- Citations: 51
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Journal articleDodd SC, Muxworthy AR, Mac Niocaill C, 2015,
Paleointensity determinations from the Etendeka province, Namibia, support a low-magnetic field strength leading up to the Cretaceous normal superchron
, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, Vol: 16, Pages: 785-797, ISSN: 1525-2027- Author Web Link
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- Citations: 7
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