Nanoscale Analysis of Superparamagnetic Systems

The paper refers to a kind of nanoscale characterization of superparamagnetic materials above and below the so-called blocking temperature. It is propose to apply the Stoner-Wohlfarth model of nanoparticles magnetization supplemented by the two-level kinetic model, determining behavior in T>0. This approach allows determination of distribution of magnetic moments and energetic barriers of magnetic objects based on magnetization curves. In many cases, the determined distribution of magnetic moments can be recalculated into average size of the magnetic objects giving finally a nano/microscaled picture of the material. The proposed method was successfully used in characterization of diluted magnetics, nanocomposites, powders and even for human hemoglobin. In the paper the basic theory and its application to the nanoscale characterization is discussed in detail.