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

Nathan Church, Joshua M. Feinberg, Richard Harrison

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

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.

Original languageEnglish (US)
Article numberQ07Z27
JournalGeochemistry, Geophysics, Geosystems
Volume12
Issue number7
DOIs
StatePublished - Mar 1 2012

Keywords

  • Domain wall
  • FORC
  • Low temperature
  • Pinning
  • Susceptibility
  • Titanomagnetite

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