The Barkhausen Effect

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Abstract
An account is given of further experiments on the Barkhausen effect in cylindrical ferromagnetic specimens. The form of the decay of induction following a Barkhausen discontinuity has been investigated and there is reasonable agreement between the theory given and the experimental results. As a result of this investigation it has been possible to satisfy the different conditions which are necessary for the detection of the discontinuities so as to obtain (a) accurate reproduction of the form of the discontinuities and (b) maximum sensitivity in the counting experiments. The number and size of the discontinuities are measured, and an estimate is made of the contribution of the discontinuous processes to the total change in magnetization over the relevant part of the hysteresis curve. Discontinuous changes in magnetic moment greater than 0.3 × 10-6 E.M.U. (corresponding to a minimum volume of 0.9 × 10-10 cm3 for iron) account for from 47% to 86% of the total change in magnetization. This is considered in relation to associated work on reversible changes, and the nature of a Barkhausen discontinuity is briefly discussed with reference to other investigations on domain structure.