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An experiment is described that enables the statistical stability of the Preisach diagram for interacting ferromagnetic particles to be tested. The samples used were of γ—Fe2O3 dispersed in a nonferromagnetic matrix to a nominal packing density of 20% by volume. Both oriented and nonoriented samples were examined. In every case the diagram was found to be stable over most of the area bounded by the major remanence loop. The region of departure from stability occurred at the higher levels of remanent intensity. A method of calculating the diagrams using only dc measurements is given. They are then used to predict accurately the ascending remanence curve after ac demagnetization for each sample. Finally, it is shown how the experimental ascending and descending remanence curves, which could not be explained by Wohlfarth's relations [J. Appl. Phys. 29, 595 (1958)] based on noninteracting particles, can be completely described in terms of the Preisach diagram.

Thin magnetic films of Co‐P were prepared in two somewhat different electroless cobalt solutions. The magnetic properties and the corrosion behavior of these films as a function of thickness was studied. The films exhibited high coercivities with a maximum of about 1000 oe at a thickness of 600Aå. The magnetic moment of these films was found to decrease on exposure to high humidity and moderate temperatures (40°–70°C); this was used as a means of studying the extent of corrosion. The extent of corrosion was found to vary as the 2/3 power of the thickness of the film.