Barkhausen jumps in soft magnetic materials at low fields

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Abstract
A new theory of Barkhausen jumps is proposed, which depicts the movement of 180° Bloch walls as due to kinks bounded by Néel lines. These lines can be pinned on dislocations. Two activation energies are introduced, one of them for small jumps in low fields and low temperatures (pinning energy), the other one for line nucleation energy. An expression of the coercive field is given. After-effect phenomena can be explained by the same physical processes. Comparison is made with recent experiments [3, 4]. It is suggested that the variation in size of Barkhausen jumps with field partially reflects the short-range order of pinning defects, and also a change in behaviour with the density of Néel lines (flexible when they behave independently one from the other, rigid when they interact)