Motion of Individual Domain Walls in a Nickel-Iron Ferrite

In footnote (20) to a paper 1 of the above title it was asserted that the theory of magnetic after-effect* given by L. N6el2 leads to zero loss for large motions of a 180° domain wall. It has since become clear that this assertion is based on a misinterpretation of Section 10 of Neel's paper, and is therefore not correct. In fact, Professor N6el has pointed out in a private communication that if the general analysis in his paper is used to calculate the viscous drag on a 180° domain wall, a result substantially the same as that given by equation (38) in Reference 1 is obtained. Neel's theory therefore does not lead to a result inconsistent with the domain wall data given in Reference 1; it appears to be possible to account for this set of data with either his theory or the analysis presented in Reference 1. The following is a derivation, which is due to Neel, of the result which is to be compared with equation (38) in Reference 1. We start from equation (26) of Reference 2, and use Neel's notation: (1)