Some notes on "superposition" in digital magnetic recording

Reasons for, and the character of, deviations from the "superposition" principle which is customarily used in considerations about digital magnetic recording are analyzed. First, a treatment is presented which is based on the Preisach model and ignores the demagnetizing field. It is shown that superposition is inconsistent with the Preisach model but that, when more than two transitions are involved, a weaker form of the superposition principle can be derived from the Preisach model. Next, the effects produced by the demagnetizing field in the medium are illustrated by results of a "self-consistent" computation for a thin layer. Finally, some experimental results obtained from a large-scale simulation model are presented.