Magnetic vortex effects on first-order reversal curve (FORC) diagrams for greigite dispersions

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Title: Magnetic vortex effects on first-order reversal curve (FORC) diagrams for greigite dispersions
Authors: Valdez-Grijalva, MA
Muxworthy, AR
Williams, W
ó Conbhui, P
Nagy, L
Roberts, AP
Heslop,, D
Item Type: Journal Article
Abstract: First-order reversal curve (FORC) diagrams are used increasingly in geophysics for magnetic domain state identification. The domain state of a magnetic particle is highly sensitive to particle size, about which FORC diagrams provide valuable information. However, the FORC signal of particles with nonuniform magnetisations, which are the main carrier of natural remanent magnetisations in many systems, is still poorly understood. In this study, the properties of non-interacting, randomly oriented dispersions of greigite (Fe3S4) in the uniform single-domain (SD) to non-uniform single-vortex (SV) size range are investigated via micromagnetic calculations. Signals for SD particles () are found to be in excellent agreement with previous SD coherent-rotation studies. A transitional range from to is identified for which a mixture of SD and SV behaviour produces complex FORC diagrams. Particles have purely SV behaviour with the remanent state for all particles in the ensemble in the SV state. It is found that for SV ensembles the FORC diagram provides a map of vortex nucleation and annihilation fields and that the FORC distribution peak should not be interpreted as the coercivity of the sample, but as a vortex annihilation field on the path to saturation.
Issue Date: 1-Nov-2018
Date of Acceptance: 16-Aug-2018
ISSN: 0012-821X
Publisher: Elsevier
Start Page: 103
End Page: 111
Journal / Book Title: Earth and Planetary Science Letters
Volume: 501
Copyright Statement: © 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (
Sponsor/Funder: Natural Environment Research Council (NERC)
Funder's Grant Number: NE/G004617/1
Keywords: 02 Physical Sciences
04 Earth Sciences
Geochemistry & Geophysics
Publication Status: Published
Online Publication Date: 2018-08-31
Appears in Collections:Faculty of Engineering
Earth Science and Engineering

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