Thermal variable variance Preisach-Neel model

Summary form only given. The demand for high-density magnetic recording media requires smaller ferromagnetic entities that are more sensitive to relaxation phenomena. To model the magnetization processes of these media one have to take that into account. It is well known that the Preisach-Neel models are well equipped for that purpose. In Preisach modeling it has been shown that, especially in perpendicular media, the static statistical interactions distribution variance is strongly dependent on the magnetic state of the sample. Recent micromagnetic simulations have confirmed this assumption. In systems in which relaxation has an important role, such as the nanoparticulate ferromagnetic ensembles, the interaction variance is changing due to this factor too. Since the cause of static statistical interactions is the field created by the blocked particles, as the temperature increases and the number of blocked particles decreases, the interaction distribution variance is also decreasing. We shall refer to this effect as to the thermal variable variance. In this paper the authors present a Preisach-Neel type model with thermal variable variance. The ensemble of nano-particle can be described by a matrix of representative points that were chosen to characterize zones in the Preisach plane with the same magnetic moment. A non-linear Stoner-Wohlfarth energy barrier is considered that, allows the study of the influence of particle orientation.