O modelo de Stoner-Wohlfarth com temperatura e interação entre as nanopartfculas magnéticas.

Abstract

The nanomagnetism has bccn extensively studie<l in reccnl years, due mainly to its various possibilities of applications. Enough ernphasis has becn given to the rnagnctic nanoparticlcs. ln this contexl, the present study aims to present and generalize the first model used to dcscribe thc magnetism of small particles, which was developed by Stoner and Wohlfarlh in 1948, known as Lhe Stoner-Wohlfarlh model. H is considered a small single-domain magnetic particle, uniaxial anisotropy, maintained aL T = O K and not interacling. ln Lhis case, the energy exchange between Lhe spins of the parLicle is constant and plays no role in encrgy minimization. Consequently Lhere is a compclilion uet.ween anü;otropy energy of t.he partide and thE> effect of Lhe applied field. Wit h this model, onc can study t.he bchavior of magnetizatiou of a single particle, as well as an arrangement of particles as a function of the applied field (bysteresis curve). With this, it is possiblc to obtaiu important information as Lhe coercive field an<l t.he rcmanent rna.gnetiza.tion. The generalizat.ion of the model iuvolved the inclusion of the effect of temperature in the system, through relaxation model of Arrenius-Néel and calcula.ting the cffed of magnetic interactions (dipolar or Exchange) between the partides, by means of mean ficld approximation model. Finally, we will use the graphics of Henkel to analy7.e the existence of thc interaction, and thc curves of óM to gct infonnation about thc t.ype and the intcnsit.y of them.