Magnetic properties and dipolar interactions of Fe3O4 nanoparticle clusters produced by bottom-up self-assembly

Abstract

Magnetic nanoparticles (MNPs) exhibit unique magnetic behaviors that make them highly applicable in various fields such as biomedical technology, energy, and sensing. This study investigates the magnetic properties and dipolar interactions of Fe₃O₄ nanoparticle clusters with different average sizes (27.4 nm, 79.2 nm, and 112.9 nm) produced by an emulsion-based bottom-up self-assembly process. The MNPs, with an individual size of 9.8 nm, were organized into clusters, and their collective magnetic properties were explored using detailed DC and AC magnetic studies. We applied a phenomenological mean-field model to describe the magnetic behavior of the clusters, including an increase in blocking temperature, energy barriers, and relaxation dynamics as a function of cluster size. The results indicate a significant influence of dipolar interactions on the energy barriers and magnetic moment dynamics, with larger clusters exhibiting stronger dipolar fields. Our findings provide insights into the interaction between nanoparticle arrangement and magnetic properties, which offers potential for the development of novel magnetic materials for advanced applications.