Influence of the magnetic interactions on the reversal mode of magnetic recording particles

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Abstract
In an assembly of particles, as used in magnetic recording media, there are always magnetic interactions. The magnetic properties of the media are modified as a consequence of the effect of such interactions on the magnetic behavior of the particles. In this work an attempt is made to find an experimental correlation between the presence and strength of the interactions and the magnetization reversal of the particles. The reversal mode is investigated by rotational hysteresis measurements and by the evolution of the angular dependence of the coercivity in samples of iron oxides at different dilution degrees. The magnetic interactions are evaluated with measurements of the remanence curves. It is found that when the magnetic interactions among the particles increase, the parameters used to study the reversal mode evolve from the behavior typical of the incoherent magnetization processes to behaviors which can be considered as intermediate between coherent and incoherent reversal modes. This evolution can be attributed to the tendency of the magnetic interactions to increase the percentage of particles in the aggregate, which reverse with coherent rotation, particularly in the agglomerates often present in closely packed assemblies.