Encyclopedia of Geomagnetism and Paleomagnetism

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

Magnetization, Viscous Remanent (VRM)

  • David J. Dunlop
Reference work entry
DOI: https://doi.org/10.1007/978-1-4020-4423-6_200

Introduction

Viscous magnetization is the gradual change of magnetization with time in an applied magnetic field H. Brief exposure of a ferromagnetic material to a field results in isothermal remanent magnetization (IRM). The additional remanence produced by a longer field exposure is viscous remanent magnetization (VRM). The longer the exposure time t, the stronger is the VRM.

Viscous remagnetization is the time‐dependent change of VRM or other remanences, such as thermoremanent magnetization (TRM), depositional remanent magnetization (DRM), or chemical remanent magnetization (CRM), in response to a change in the direction or strength of H. In nature, such field changes are due to secular variation, excursions, polarity transitions, or plate motion. In laboratory experiments, but never in nature, samples may be exposed to zero field and the viscous decay of their magnetization measured.

The natural remanent magnetization (NRM) of rocks, sediments, and soils usually includes a VRM...

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© Springer-Verlag 2007

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  • David J. Dunlop

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