Using minor loop behavior to investigate the Preisach distribution for particulate media

The shape of minor loops has been measured as a function of remanence for Co-coated gamma -Fe/sub 2/O/sub 3/, barium ferrite, and iron particulate media, as well as a series of particle assemblies in which particle orientation and spacing were varied. The width of the loops at zero field and their axial slope were used as quantitative measures of their shape. In all cases, the minor loops for the same field extrema but different values of average remanence are not congruent. According to an operator analysis of the Preisach model by I.D. Mayergoyz (1986), noncongruence indicates that the Preisach distribution is also a function of field history. This result is in agreement with other experimental investigations of this issue. Hence, noncongruence provides a confirmation of the analysis by Mayergoyz. The amount of noncongruence is used here to determine the degree to which the Preisach distributions for various types of particle assemblies depend on field history.<>