An Improved Method for Demagnetizing Rocks in Alternating Magnetic Fields

Abstract

A new alternating field demagnetization apparatus is described which produces peak fields of up to 200 milliweber m−2 (2000 gauss). Use is made of a special infinitely variable transformer to raise and lower the current in the demagnetizing solenoid. The apparatus has been made completely automatic which considerably speeds up routine demagnetizing procedures in palaeomagnetic investigations. Some discussion is given of the most suitable tumbling arrangement for the rock specimen and it is suggested that tumbling ratios of either 8:15 or 11:16 have some advantage over those used by other workers.