The very early experimental work in ferromagnetodynamics, which was described in sections 1.2 and 1.3, was all done using conducting magnetic materials and was more concerned with the measurement of material properties, such as eddy-current loss and permeability, than with what was then the very new concept of domain wall motion. A valuable review of the beginnings of a more microscopic approach to these problems has been given by Kittel (1946a) who considered the motion of a domain wall separating head-to-head domains in a conducting magnetic material. This rather unexpected relative orientation of adjacent domains was criticised by Néel (1951) who considered what appears to be quite natural today, the 180° domain wall motion which has been such a dominant feature of previous chapters here. The results of these calculations by Néel (1951) were still expressed by the dispersion or frequency dependence of the real and imaginary part of the permeability of the material, however, and this point of view persists in many interesting and more recent papers by Lee (1958, 1960), Bishop and Lee (1963), Mulhall (1964), Zhakov and Filipov (1974) and Filipov and Zhakov (1975) who all give good reviews of the literature.
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