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A d. c. field was applied along one of the anisotropy axes of evaporated nickel-iron films with uniaxiat anisotropy, and a small a. c. field was applied perpendicular to the d. c. field. The magnetization amplitude parallel to the a. c. field was measured. The dependence of the susceptibility, measured like this, on the d. c. field strength corresponds to the single domain theory only for films with a small Hc/H K ratio or for large d. c. fields. The deviations from the single domain theory and the losses occurring can be explained by the ripple structure of the m~gnetizatiou in polycrystalline films.

If the thickness of an intermediate nonmagnetic layer separating two ferromagnetic layers is larger than the ferromagnetic wall thickness (order of 1 μ), only a magnetostatic interaction at the film edges exists. If the intermediate-film thickness is smaller than the wall thickness, the magnetostatic interaction of the domain walls is essential, yielding special multilayer wall configurations. If the intermediate film is thinner than that necessary for a complete exchange isolation (order of 10 nm), the wall configurations are modified by an exchange coupling between the local magnetizations of the layers. The wall configurations and their influence on the wall motion and switching behavior are reviewed in this paper.

Some calculations exist for the mobility and the effective mass of ferromagnetic domain walls of special wall structures. More generally valid derivations and formulas are presented here, which are not restricted to a special wall structure. It is shown that the nonlinearity observed by several authors in the dependence of the wall velocity on the field can be predicted theoretically if the material inhomogeneities causing the coercivity are taken into account in an appropriate manner. For a special example the existence of the wall contraction and the velocity limit shown by Enz for a wall without damping and without field is shown for a wall with damping and with field. As is the approximation by Enz, the present approximation also is not able to indicate the value of this velocity limit.Fur die Beweglichkeit und die effektive Masse ferromagnetischer DomiinenwLnde sind einige Berechnungen fur spezielle Wandstrukturbeispiele bekannt geworden. Die hier wiedergegebene Rechnung ist allgemeingiiltiger und bezieht sich nicht auf eine bestimmte Wandstruktur. Es wird gezeigt, daB die verschiedentlich beobachtete Nichtlinearitiit in der AbhLngigkeit der Wandgeschwindigkeit vom angelegten Feld theoretisch zu erwarten ist, wenn man die die Koerzitivfeldstirke bestimmenden Inhomogenititen des Materials in geeigneter Weise beriicksichtigt. An einem speziellen Beispiel wird aul3erdem gezeigt, daB die von Enz fiir eine ungediimpfte Wand ohne Feld berechnete Wandkontraktion und Maximalgeschwindigkeit auch fur eine gedimpfte Wand im Feld existiert. Beide Niherungen sind jedoch nicht in der Lage, die Hohe der Grenzgeschwindigkeit sicher anzugeben.

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