Individual particle heating of interacting magnetic nanoparticles at nonzero temperature

Abstract

Interaction phenomena have become a hot topic in nanotechnology due to their influence on the performance of magnetic nanostructures for biomedical applications. Hysteresis loops give a good account of the particles’ magnetic behaviour, providing valuable clues on subsequent improvements. Nevertheless, the individual hysteresis loops of these systems are also influenced by any potential energy exchanged between the particles, and in contrast to non-interacting particles, are no longer a good measure for the local heat generated by each particle. As of today, there is no method capable of analysing the heat dissipation resulting from the nanoscale magnetisation dynamics in its full generality, i.e. in the presence of interactions and at nonzero temperature (allowing for thermally induced switching), and therefore the means of exploiting these dynamics remain hampered by a lack of understanding. In this work we address this problem by proposing and validating an equation that can be used to resolve the individual heat dissipation of interacting nanoparticles at nonzero temperature. After assessing this equation for different model systems, we have found that the proportion of heat dissipated in each individual particle tends to become more uniformly distributed for larger fields. Our results might have implications for magnetic particle hyperthermia where one of the most long-standing challenges is to achieve a homogeneous therapeutic temperature distribution in the target region during a treatment. Although tackling this issue involves a number of aspects related to the tissues involved, the injected nanoparticles, and the applied magnetic field, we believe that a more homogeneous heating of the particles inside the tumour will help to overcome this challenge.