Thermally stable maghemite formed by rapid high temperature oxidation of fine-grained synthetic magnetite

Xiuming Liu*, John Shaw, DunSheng Xia, Jianzhong Jiang, Tim Rolph

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

Abstract

Maghemite (gamma-Fe(2)O(3)) is usually synthesized by magnetite under oxidizing conditions a few hours or a few days under temperature 300 degrees C. This paper introduces maghemite formed by quick heating to 700 degrees C of synthetic fine-grained (pseudo single domain, PSD, dominantly) magnetite. This maghemite shows almost completely reversible thermomagnetic behavior between room temperature and up to 700 degrees C. We used X-ray powder diffraction and Mossbauer spectroscopy to confirm the identity of this maghemite by comparing its magnetic hysteresis, high temperature magnetization and low temperature susceptibility with those of original preheated magnetite. Our study indicates that the thermal stability of maghemite is affected not only by its purity (stoichiometry), but also by its heating temperature and duration. Almost completely thermally stable maghemite can be formed by such rapid, high temperature oxidation of fine PSD magnetite. This implies that not all maghemite is thermally unstable, and that some maghemite, produced in certain heating environments, should be able to carry thermal remanent magnetization.

Original languageEnglish
Title of host publicationMagnetic materials
Subtitle of host publicationresearch, technology and applications
EditorsJacob I. Levine
Place of PublicationNew York
PublisherNova Science Publishers
Pages265-276
Number of pages12
ISBN (Electronic)9781606921456
Publication statusPublished - 2009

Keywords

  • CHINESE LOESS DEPOSITS
  • SUSCEPTIBILITY
  • PEDOGENESIS
  • HYSTERESIS
  • DEPENDENCE
  • MINERALOGY
  • STABILITY
  • ORIGIN
  • SOIL

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