Thermoremanence and stable memory of single-domain hematites

Details Thermoremanence and stable memory of single-domain hematites Thermoremanence and stable memory of single-domain hematites

Sep 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002georl..29r..24o&link_type=abstract

Geophysical Research Letters, Volume 29, Issue 18, pp. 24-1, CiteID 1877, DOI 10.1029/2002GL015597

Mathematics

Logic

6

Geomagnetism And Paleomagnetism: Magnetic Anomaly Modeling, Geomagnetism And Paleomagnetism: Paleomagnetism Applied To Geologic Processes, Geomagnetism And Paleomagnetism: Rock And Mineral Magnetism, Planetology: Solar System Objects: Mars

Scientific paper

We report thermoremanent magnetization (TRM) intensities and thermal demagnetization behavior of seven samples of single-domain hematite (α Fe2O3) with grain sizes between 0.12 and 0.42 μm, before and after zero-field cycling through the low-temperature Morin transition (TM ~ 240 K). TRM was unaffected by 100 mT alternating field demagnetization and by 600°C thermal demagnetization. Most demagnetization occurred between 625°C and the Néel temperature of 680-690°C. The TRM memory recovered after low-temperature cycling was parallel to the original TRM and equally resistant to thermal demagnetization. TRM and TRM memory of single-domain hematites are mainly due to the hard spin-canted magnetism intrinsic to the crystal structure above the Morin transition, and not to the small and softer defect magnetism that survives below TM. However, the defect magnetism may play a role in renucleating the spin-canted magnetism in a preferred direction during warming through TM. TRM intensities are well predicted by Neél single-domain theory and increase in almost exact proportion to grain size. Although smaller than TRM intensities of multidomain hematites, single-domain TRMs are potent sources of remanent magnetic anomalies, particularly for larger grains (10-15 μm), and are likely to be more stable over geological time than multidomain hematite TRMs.

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