Direct visualization of the thermomagnetic behaviour of pseudo-single-domain magnetite particles

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Title: Direct visualization of the thermomagnetic behaviour of pseudo-single-domain magnetite particles
Authors: Almeida, T
Muxworthy, AR
Kovacs, A
Williams, W
Brown, PD
Dunin-Borkowski, RE
Item Type: Conference Paper
Abstract: The study of the paleomagnetic signal recorded by rocks allows scientists to understand Earths past magnetic field and the formation of the geodynamo. The magnetic recording fidelity of this signal is dependent on the magnetic domain state it adopts. The most prevalent example found in nature is the pseudo-single-domain (PSD) structure, yet its recording fidelity is poorly understood. Here, the thermoremanent behavior of PSD magnetite (Fe3O4) particles, which dominate the magnetic signatures of many rock lithologies, is investigated using electron holography. This study provides spatially resolved magnetic information from individual Fe3O4 grains as a function of temperature, which has been previously inaccessible. A small exemplar Fe3O4 grain (~150 nm) exhibits dynamic movement of its magnetic vortex structure above 400°C, recovering its original state upon cooling, whereas a larger exemplar Fe3O4 grain (~250 nm) is shown to retain its vortex state on heating to 550°C, close to the Curie temperature of 580°C. Hence, we demonstrate that Fe3O4 grains containing vortex structures are indeed reliable recorders of paleodirectional and paleointensity information, and the presence of PSD magnetic signals does not preclude the successful recovery of paleomagnetic signals.
Issue Date: 15-Apr-2016
Date of Acceptance: 23-Mar-2016
ISSN: 2375-2548
Publisher: American Association for the Advancement of Science
Journal / Book Title: Science Advances
Volume: 2
Issue: 4
Copyright Statement: Copyright © 2016, The Authors This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited.
Sponsor/Funder: Natural Environment Research Council (NERC)
Funder's Grant Number: NE/J020508/1
Keywords: Palaeomagnetism
in situ transmission electron microscopy
off-axis electron holography
pseudo–single-domain states
thermo-remanent magnetisation
thermomagnetic behavior
Publication Status: Published
Open Access location:
Appears in Collections:Earth Science and Engineering

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