Domain Structures Due to Induced Anisotropy and Stresses in Film Heads

The local anisotropy, near the backgap closure of inductive-film heads, is generally the result of two superimposed anisotropies. One is the anisotropy induced during deposition of the magnetic yoke in the presence of a magnetic field and the other is a stress anisotropy whose magnitude and direction depend on the sign and magnitude of the stress-magnetostriction product. It will be shown that if it is assumed that 180-degree domain walls always follow the direction of the local anisotropy, then domain patterns can be used to deduce the local stress-magnetostriction product. We will present a simple model for these combined anisotropies and the associated domain wall patterns assuming that the stress-magnetostriction product falls off as r², where r is the distance from the center of the backgap closure, which in this case is assumed to be circular. One of the features of the predicted domain wall patterns is a three wall intersection occurring where the two anisotropies cancel. i.e. where the yoke material is isotropic. Examples of domain walls in the vicinity of a back-gap closure of an experimental film head are shown and discussed. © 1989 IEEE