CONICET | Buscador de Institutos y Recursos Humanos

Magnetic hyperthermia is being developed as a cancer treatment and consists on the incorporation of magnetic nanoparticles (NPs) on a tumor with their subsequent heating through the application of an alternating magnetic field. In this work, we present a study of the effect of the dipolar interactions between NPs on the area of the magnetization hysteresis loops. We considered NPs arranged in chains with uniaxial anisotropy (Fig.1), similarly to magnetosomes . The magnetic behavior of the NPs is described by a previous model that considers the effects of temperature, as well as the frequency of the field sweep. In this new model, which goes beyond the linear response theory , the magnetic field is corrected with interparticle interactions. Through its implementation, the case of low and high interaction was studied, varying the orientation regarding the external magnetic field (Φ ).To analize these interactions, the parallel (H ) and perpendicular (H ) components of the dipolar magnetic field, regarding the external one, were taken into account. An increment in the area of the hysteresis loops due to dipolar interaction is reported (Fig.2), either for isolated chains with a certain Φ or for randomly-oriented chains, which represents a higher specific absortion rate (SAR). It was seen that both components of the dipolar field present hysteresis as the external field is swept. It was also determined that H is always in phase with the magnetization loop and helps to increase its area, meanwhile H presents a in- to anti-phase transition near Φ =3π/8. This last component can or cannot help to increase the area, depending on the strength of the interaction.To conclude, dipolar interactions in these kind of systems can help to improve hyperthermia ignificantly for some which can originally be far from the ideal conditions for experiments.

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