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| Titel |
Cooling rate dependence of the TRM of SD, PSD and MD particles |
| VerfasserIn |
A. Ferk, R. Leonhardt, K.-U. Hess, S. Koch, D. Krasa, R. Egli, M. Winklhofer, D. B. Dingwell |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063150
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| Zusammenfassung |
| The dependence of thermoremanence (TRM) on cooling rate was investigated experimentally
on six thermally stabilized synthetic magnetites that are sealed in quartz glass tubes and range
in grain size from below 1 μm (single domain, SD) to 12.1 μm (multi domain, MD). Earlier
theoretical and experimental studies suggest that TRM dependence on cooling rate varies
with grain size: For non-interacting SD grains slower cooling was found to lead to larger
TRMs, for MD assemblages lower TRM acquisition after slow cooling has been suggested
and for PSD grains studies have given various results (similar to SD behavior, no cooling
rate dependence at all, opposite to SD behavior). Here, we present cooling rate
experiments with well defined cooling rates over the whole blocking spectrum
that were repeated several times to obtain uncertainty estimates. Rock magnetic
measurements before and after the cooling rate experiments are done to check for alteration.
During heating and cooling of the samples a magnetic field of 50 μT was applied
parallel to the y-axis. The samples were cooled using five different cooling rates
(0.1 to 15K/min; at least 3 repeat measurements). Additionally four samples were
cooled with a very slow cooling rate of 0.05K/min (two repeat measurements). After
each cooling the horizontal component of the magnetization was measured using
a 2G Cryogenic magnetometer. The theoretically predicted log-linear behavior
for SD grains is verified though the magnitude of the effect is smaller than in the
predictions. The same is observed for two samples with pseudo-single domain (PSD)
grains. For two of the MD samples no effect is found while the third one shows
some increase of TRM with slower cooling rate like the SD and PSD samples. |
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