Encyclopedia of Geomagnetism and Paleomagnetism

2007 Edition
| Editors: David Gubbins, Emilio Herrero-Bervera

Microwave Paleomagnetic Technique

  • John Shaw
Reference work entry
DOI: https://doi.org/10.1007/978-1-4020-4423-6_217

The microwave technique is used to determine the strength of the Earth's magnetic field in the past. It is usually applied to igneous rock such as lava and dike or the surrounding material that has been heated by them (baked contact), as well as heated archaeological material (ceramics, fireplaces, etc.). Samples are placed inside a resonant cavity and exposed to microwaves for a few seconds (typically 10 s). The microwave exposure is directly analogous to raising the temperature of the sample in the conventional Thellier technique, the main difference being that when the sample is exposed to microwaves most of the energy is absorbed by the magnetic system whereas in direct heating the entire sample absorbs energy.

By concentrating the energy in the magnetic system the bulk sample is not heated significantly. This reduces the probability of laboratory thermal alteration and provides a more accurate determination of the ancient magnetic field strength.

Microwaves magnons and temperature

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Bibliography

  1. Hill, M.J., and Shaw, J., 2000. Magnetic field intensity study of the 1960 Kilauea lava flow, Hawaii, using the microwave palaeointensity technique. Geophysical Journal International, 142: 487–504.CrossRefGoogle Scholar
  2. Hill, M.J., Gratton, M.N., and Shaw, J., 2002. A comparison of thermal and microwave palaeomagnetic techniques using lava containing laboratory induced remanence. Geophysical Journal International, 151: 157–163.CrossRefGoogle Scholar
  3. Walton, D., Shaw, J., Share, J.A., and Hakes, J., 1992. Microwave demagnetisation. Journal of Applied Physics, 71: 1549–1551.CrossRefGoogle Scholar
  4. Walton, D., Share, J.A., Rolph, T.C., and Shaw, J., 1993. Microwave magnetisation. Geophysical Research Letters, 20: 109–111.Google Scholar

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • John Shaw

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