Gyroremanent magnetization produced by specimen rotation between successive alternating field treatments

Summary. On the basis of existing theories of rotational remanent magnetization, it is predicted that a gyroremanent magnetization (GRM) might be induced in an isotropic specimen whose orientation is changed during the interval between successive alternating field treatments. An expression is derived, relating the relative magnitude of GRM to the angular displacement, θ of a specimen about an axis perpendicular to the alternating field axis. The predicted effects were observed for four of the five specimens investigated, and in each case GRM was of comparable magnitude to the corresponding partial rotational remanent magnetization. Hysteresis loop curves and characteristics are all consistent with a main magnetic component comprising magnetite grains. A possible connection between GRM and another form of GRM reported in the case of an anisotropic specimen is suggested. Demagnetization of isotropic (and anisotropic) samples by means of the multi-axis technique might be adversely affected by production of GRM.