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About IIG Observatory Instruments and Facilities

Alternating Field (AF) Demagnetizer

Instrument Details
Name: AF Demagnetizer
Made: Molspin Ltd, UK.

Peak Field : up to 1000 Oe and 1500 Oe
Sensitivity : 1.2V

A weak alternating field is applied to the specimen, causing the magnetization of grains of low coercivity to follow the applied field. As this field is reduced, the magnetization of the particles left in random positions, i.e., in the direction of the 'easy' axes. As many thousands of grains will be affected, even over a short field range, the magnetization of such particles becomes effectively randomized if the 'easy' axes are randomly oriented, leaving only the remanence of the particles with coercivities greater than that of the applied field, with the remanence of the specimen measured after each increment, allow the coercivity spectra to be analyzed very finely up to maximum applied field of the instrument (150 mT).

This instrument is used in palaeomagnetic investigations to demagnetize the rock specimens and thus to remove the unwanted viscous and/or secondary components to isolate the ChRM directions.

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