Magnetic Remanence Related to Slow Rotation of Ferromagnetic Material in Alternating Magnetic Fields

The experiments described in this paper show that a permanent remanence can be induced in a ferromagnetic specimen if it is rotating even very slowly, during the slow decrease of an alternating field pervading the specimen. The remanence is antiparallel to the rotation vector, when the rotation axis is perpendicular to the alternating field axis. The result therefore seems incompatible with existing electromagnetic theories for rotating conducting paramagnetic bodies, but the solution for ferromagnetic bodies might still be compatible with Maxwell's equations. Precautions were taken to ensure that the remanence was neither an anhysteretic remanence, nor other spurious remanence. From the practical point of view, the results are relevant to the design of alternating field demagnetization equipment, such as is used by palaeomagnetists to separate various components of magnetization in a single specimen. Without care in design, a spurious remanence could be induced by the ‘tumbling’ of the specimen.