Year: 2024
Type: article
Abstract: Magnetic hysteresis measurements are routinely made in the Earth and planetary sciences to identify geologically meaningful magnetic recorders, and to study variations in present and past environments. Interpreting magnetic hysteresis data in terms of domain state and paleomagnetic stability are major motivations behind undertaking these measurements, but the interpretations remain fraught with challenges and ambiguities. To shed new light on these ambiguities, we have undertaken a systematic micromagnetic study to quantify the magnetic hysteresis behavior of room‐temperature magnetite as a function of particle size (45–195 nm; equivalent spherical volume diameter) and shape (oblate, prolate and equant); our models span uniformly magnetized single domain (SD) to non‐uniformly magnetized single vortex (SV) states. Within our models the reduced magnetization associated with SV particles marks a clear boundary between SD (≥0.5) and SV (<0.5) magnetite. We further identify particle sizes and shapes with unexpectedly low coercivity and coercivity of remanence. These low coercivity regions correspond to magnetite particles that typically have multiple possible magnetic domain state configurations, which have been previously linked to a zone of unstable magnetic recorders. Of all the hysteresis parameters investigated, transient hysteresis is most sensitive to particles that exhibit such domain state multiplicity. When experimental transient hysteresis is compared to paleointensity behavior, we show that increasing transience corresponds to more curved Arai plots and less accurate paleointensity results. We therefore strongly suggest that transient behavior should be more routinely measured during rock magnetic investigations.
DOI: 10.1029/2024gc011461
Authors: Greig A. Paterson, Roberto Moreno, Adrian R. Muxworthy, Lesleis Nagy, Wyn Williams, Lisa Tauxe
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,890
Awards: Determining ancient magnetic field strengths from the Earth and Solar System, G2290079365, Paleointensity extremes: Dynamic implications and future fields, G2682539759, G2976859837, G3449279021, G3486560075, G3609742038, NSFGEO-NERC: Transforming understanding of paleomagnetic recording: Insights from experimental observations and numerical predictions, G433235953, G5684403828, G6663982800, G7539028823, NSFGEO-NERC: The history of the Earth's magnetic field strength over the last five million years: Filling in the southern hemisphere gap, Thermochemical remanent magnetisations: How do they affect ancient magnetic field intensities from the Earth and Solar System?, VIRGIL: The VIRtual paleomaGnetIc Laboratory, G8228517516, G8384240328, Particles to Planets: Unravelling the history of our magnetic field, G949327431
OpenAlex ID: W4401844005