Abstract
Summary An analysis of the bulk reaction to alternating field (AF) demagnetization of an assemblage of intrinsically anisotropic grains is performed in order to determine the difference between tumbling and 3-axis AF demagnetization of an isothermal remanent magnetization (IRM). Two models are used to describe the anisotropic behaviour of the individual grains. The first is the Stoner-Wohlfarth theory for non-interacting monodomain grains with uniaxial anisotropy and coherent rotation of magnetization. The second model is that the effective demagnetizing field is that component of the actual demagnetizing field parallel to the easy demagnetization axis of the grain. The second model provides a theoretical explanation for the experimental results obtained by Rimbert. From this a simple method is suggested using IRMs with AF demagnetization for gaining additional information regarding the type of grains in which a magnetization resides. Finally it is suggested that multi-axis AF demagnetizes should be used in order to allow the directional coverage provided by tumbling demagnetizers while avoiding the problem of rotational remanent magnetization (RRM).
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