Demagnetization of Layered Ferromagnetic Structures for Magnetically Shielding: Frequency Considerations

This paper provides the background for evaluating the appropriate frequency from measured or manufacturer provided magnetic permeability data. The proper frequency is, among other parameters, a necessary prerequisite for the low residual field demagnetization required for several applications including biomagnetism and particle physics. The paper also presents an interpretation of the material-dependent effects which arise during the demagnetization procedure. The interpretation focuses on magnetic diffusion influenced by magnetic permeability variation accompanying the demagnetization process. Explanations based on energy considerations show how the domain alignment is affected during the demagnetization process. A comparison with the results obtained from an algebraic hysteretic model supports the conclusions.