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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 paperBerndt T, Muxworthy AR, 2015,
Viscous remanent magnetization dating of cataclysmic floods in Iceland
, IUGG 2015 -
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 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: 59
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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: 9
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Journal articleMuxworthy AR, Williams J, Heslop D, 2015,
Testing the use of viscous remanent magnetisation to date flood events
, Frontiers in Earth Science, Vol: 3Using erratics associated with large flood events, this paper assesses whether their viscous remanent magnetisation (VRM) can be used to date the flood events. We tested this method using flood erratics from three large events: (1) the Late Pleistocene Bonneville mega-flood in Idaho, USA, (~14–18 ka), (2) the 1918 A.D. Mt. Katla, Iceland, eruption and associated jökulhaup (meltwater flood) at Mýrdalssandur, and (3) the Markarfljót jökulhaup due to an earlier eruption of Mt. Katla (~2.5 ka). We measured 236 specimens, 66 of which yielded clear identifiable and measurable viscous magnetisation signals from erratics with clustered VRM directions. From the VRM unblocking temperatures, age estimates were made. The age estimate for the most recent event (Mýrdalssandur) worked well, with a median estimated age of 80 years (with individual erratic estimates distributed between 61–105 years) compared to the known age of 91 years. The ages of the other two events were over-estimated. The estimates for Markarfljót [15 ka (7–33 ka)] were based on the results of just one erratic. For the Bonneville flood the estimates were too old, however, this locality had the largest uncertainty in the ambient temperature used in the age determination; the VRM acquired is strongly dependent on the ambient temperature, the older the event the greater the uncertainty. Southern Idaho currently has hot summers, with average summer maximum temperatures of ~31°C, but a mean annual temperature of only ~ 9°C. It is suggested that the VRM dating method works best for recent events (<2–3 ka) where the ambient temperature history can be constrained.
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Conference paperBerndt T, Muxworthy AR, 2015,
Temperature and grain size dependence of the attempt time \tau_{0} for fine magnetic particles (poster)
, Magnetic Interactions 2015 -
Conference paperSupakulopas R, Muxworthy AR, Døssing A, et al., 2015,
The magnetic properties and palaeodirections of basalts in Iceland: preparation to test the geocentric axial dipole hypothesis (GAD) (poster)
, Magnetic Interactions 2015 -
Conference paperBalikova D, Maidment S, Muxworthy AR, 2015,
The age of the Morrison Formation (Western Interior, USA): A Magnetostratigraphic Approach (poster)
, Magnetic Interactions 2015 -
Conference paperMuxworthy AR, Almeida T, Williams W, et al., 2015,
Observing remanence structures in sub- micron magnetite at high-temperatures
, Magnetic Interactions 2015 -
Conference paperShah J, Muxworthy AR, Genge M, 2015,
A micro-CT approach to the paleomagnetic conglomerate test
, Magnetic Interactions 2015 -
Conference paperValdez Grijalva M, Muxworthy AR, Williams W, 2015,
Micromagnetics of individual greigite SD and PSD grains
, Magnetic Interactions 2015
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