A possible magnetic after‐effect caused by diffusion of axially symmetric point defects

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Abstract
Point defects possessing a symmetry axis will tend to align preferentially with respect to the local magnetization direction in a ferromagnet; this produces a time dependence of the permeability known as the magnetic after effect. Many such point defects may be expected to diffuse by repeated application of these orientation‐jumps processes. This should also give rise to a magnetic after effect with a much longer time scale. The theory of this effect is developed with particular application to interstitial atoms or double half vacancies in a b.c.c. metal, although much of the formalism has more general applicability. Quantitative calculations are carried out for 〈100〉‐90° Bloch walls. The results depend strongly upon whether the defect orientation can follow the changes in magnetization needed to measure the permeability. If the defects can follow, the results are essentially the same as those obtained by DIETZE [5] for diffusion of ordinary vacancies. If the defects cannot follow, the after effect should persist for longer times than with the case of ordinary diffusion, and the possibility exists that, depending upon the values of two as yet unknown parameters, the effect may have an anomalous sign.