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Science 24 February 1989:
Vol. 243. no. 4894, pp. 1043 - 1047
DOI: 10.1126/science.243.4894.1043
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Articles

Chemico-Viscous Remanent Magnetization in the Fe3O4-yFe2O3 System

ÖZDEN ÖZDEMIR 1 and DAVID J. DUNLOP 1

1 Geophysics Laboratory, Department of Physics, University of Toronto, Toronto, Canada M5S 1A7.

The chemical remanent magnetization (CRM) acquired when single-domain size magnetite (Fe304) oxidizes to maghemite (ggrFe2O3) in a 50-microtesla field at a series of 13 temperatures from 1000 to 6560C is of similar intensity to viscous remanent magnetization (VRM) acquired under the same field and temperature conditions by unoxidized magnetite. The remanences of the oxidized and unoxidized phases also have similar resistances to demagnetization. These similarities imply that the remanence of the oxidized material is a chemico-viscous remanent magnetization (CVRM) having some of the characteristics of both classic growth CRM and thermally activated VRM. At low temperatures in partially oxidized grains, VRM of the magnetite core and growth CRM of the maghemite surface layer contribute about equally to CVRM. Near the Curie point, intensity of CVRM increases to a Hopkinson-type peak. High-temperature CVRM is more resistant to demagnetization than the thermoremanent magnetization (TRM) produced from cooling through the Curie point.

Submitted on October 12, 1988
Accepted on December 22, 1988


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Viscous remanent magnetization of high thermal stability in limestone.
G. J. Borradaile (1999)
Geological Society, London, Special Publications 151, 27-42
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