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| Titel |
Lamellar magnetism: its physical basis and rock-magnetic significance |
| VerfasserIn |
K. Fabian, S. A. McEnroe, P. Robinson, V. P. Shcherbakov |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027339
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| Zusammenfassung |
| Lamellar magnetism is a type of magnetic remanence, carried by uncompensated magnetic
moments in monolayers at interfaces between nanoscale exsolution structures of
antiferromagnetic hematite and paramagnetic ilmenite. Lamellar remanence is commonly
found in rocks which have a very low susceptibility, implying a low concentration of
magnetic oxides. Remanence in these rocks is considerably higher than the induced
magnetization, resulting in high Q-ratios which can be larger than 100. During recent years,
lamellar magnetism has advanced from a hypothesis into an experimentally and theoretically
verified theory. The main steps of this development will be outlined in this presentation, and
possible implications for other mineral systems will be discussed. There remain a number of
open questions. Most important for paleomagnetic studies is the acquisition of
lamellar NRM during cooling and the exsolution process. Experiments indicate that
this NRM acquisition is extremely efficient, which poses strong constraints on the
physical processes involved. Studies on several magnetic anomalies have shown
that, when coexisting MD magnetite is present, it increases rather than decreases
coercivity, intensity, and even Q-values. A possible explanation is magnetostatic
coupling between the highly efficient lamellar NRM and the magnetically soft MD
magnetite. |
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