Short-term viscous effects on measurements of remanance

Summary. The magnetic remanence of some rock specimens, when measured in mu-metal shielded magnetometers, appear to include a rapidly acquired (<3-5 s), but slow decaying (> 100 s) component that has a characteristic direction for each magnetometer, which seems to be related to the sequence of specimen positions during measurement. This spurious remanence can be mistaken for a stable, linear, geologically meaningful magnetic vector. The effect can be partially reduced by passing a small current through a coil wound around the mu-metal opening, and largely, but not completely, eliminated by placing the magnetometer in field-free space.