Low-temperature domain wall pinning in titanomagnetite: Quantitative modeling of multidomain first-order reversal curve diagrams and AC susceptibility

Church, Nathan and Feinberg, Joshua M. and Harrison, Richard J. (2011) Low-temperature domain wall pinning in titanomagnetite: Quantitative modeling of multidomain first-order reversal curve diagrams and AC susceptibility. G3 Geochemistry Geophysics Geosystems, 12. Q07Z27. ISSN 1525-2027 DOI 10.1029/2011GC003538

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Abstract

Domain wall pinning in titanomagnetite has been investigated at low temperatures using first-order reversal curve (FORC) diagrams, AC magnetic susceptibility, and Lorentz transmission electron microscopy. A discontinuous transition from a low-coercivity extrinsic pinning regime to a high-coercivity intrinsic pinning regime is evident in low-temperature FORC diagrams on cooling from 100 to 50 K. Intrinsic pinning is characterized by a “crescent moon” FORC distribution with narrow coercivity distribution centered on 10–20 mT. This crescent-shaped FORC distribution is reproduced using a modification of Néel's (1955) one-dimensional theory of domain wall pinning in a random field. The pinning transition coincides with a thermally activated relaxation process (activation energy 0.13 ± 0.01 eV), attributed to electron hopping. The relaxation and intrinsic pinning are explained as a magnetoelastic aftereffect caused by enhancement of magnetocrystalline anisotropy due to rearrangement and localization of Fe2+−Fe3+ cations within the domain walls. This study provides experimental verification that Néel's theory is an appropriate quantitative framework for the analysis of FORC diagrams in multidomain titanomagnetite and suggests a potential method for the quantitative unmixing of multidomain signals from FORC diagrams in rock and environmental magnetic studies.

Item Type: Article
Uncontrolled Keywords: 2011AREP; IA63;
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: G3 Geochemistry Geophysics Geosystems
Volume: 12
Page Range: Q07Z27
Identification Number: 10.1029/2011GC003538
Depositing User: Sarah Humbert
Date Deposited: 21 Oct 2011 16:58
Last Modified: 23 Jul 2013 10:02
URI: http://eprints.esc.cam.ac.uk/id/eprint/2209

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