Magnetic Anisotropy of the Demagnetized State

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Abstract
An isotropic polycrystalline substance, demagnetized in a slowly decreasing alternating field, is in general magnetically anisotropic. The magnetization curve J(H) in a given direction will depend on the angle between H and the direction of demagnetization. We have compared the two magnetization curves for φ=0 and φ=π/2. Their difference is a maximum for a field of 0.75 Hc, and can be more than 60% of J. This effect does not exist in substances with uniaxial magnetic anisotropy like hexagonal Co, or in samples with large internal stresses. We have also investigated the variation of the anisotropy of the demagnetized state of a sample which was made progressively more uniaxial by an increasing stress. Furthermore, if a complete demagnetization is followed by a partial demagnetization in the perpendicular direction, this partial demagnetization only modifies the initial state if a certain critical field is exceeded. We have determined some characteristics of this critical field.