The vortex state in geologic materials: a micromagnetic perspective

Lascu, I., Einsle, J. F. , Ball, M. R. and Harrison, R. J. (2018) The vortex state in geologic materials: a micromagnetic perspective. Journal of Geophysical Research: Solid Earth, 123(9), pp. 7285-7304. (doi: 10.1029/2018JB015909)

205241.pdf - Published Version



A wide variety of Earth and planetary materials are very good recorders of paleomagnetic information. However, most magnetic grains in these materials are not in the stable single domain grain size range but are larger and in nonuniform vortex magnetization states. We provide a detailed account of vortex phenomena in geologic materials by simulating first‐order reversal curves (FORCs) via finite‐element micromagnetic modeling of magnetite nanoparticles with realistic morphologies. The particles have been reconstructed from focused ion beam nanotomography of magnetite‐bearing obsidian and accommodate single and multiple vortex structures. Single vortex (SV) grains have fingerprints with contributions to both the transient and transient‐free zones of FORC diagrams. A fundamental feature of the SV fingerprint is a central ridge, representing a distribution of negative saturation vortex annihilation fields. SV irreversible events at multiple field values along different FORC branches determine the asymmetry in the upper and lower lobes of generic bulk FORC diagrams of natural materials with grains predominantly in the vortex state. Multivortex (MV) FORC signatures are modeled here for the first time. MV grains contribute mostly to the transient‐free zone of a FORC diagram, averaging out to create a broad central peak. The intensity of the central peak is higher than that of the lobes, implying that MV particles are more abundant than SV particles in geologic materials with vortex state fingerprints. The abundance of MV particles, as well as their single domain‐like properties point to MV grains being the main natural remanent magnetization carriers in geologic materials.

Item Type:Articles
Additional Information:This research has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007‐2013)/ERC grant agreement 320750.
Glasgow Author(s) Enlighten ID:Einsle, Dr Joshua Franz
Authors: Lascu, I., Einsle, J. F., Ball, M. R., and Harrison, R. J.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences > Earth Sciences
Journal Name:Journal of Geophysical Research: Solid Earth
ISSN (Online):2169-9356
Published Online:23 August 2018
Copyright Holders:Copyright © 2018 American Geophysical Union
First Published:First published in Journal of Geophysical Research: Solid Earth 123(9)7285-7304
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

University Staff: Request a correction | Enlighten Editors: Update this record