Seminar Theo Duarte

Magnetic-field-mediated Assembly Of Iron Nanoparticles Into Superstructures Toward Rare-earth-Free Magnets

Affiliation: Théo Duarte De Assuncao, Laboratoire de Physique et Chimie des Nano-Objets (LPCNO), INSA Toulouse, Université de Toulouse.

Abstract:

The development of rare-earth-free permanent magnets is a major challenge for sustainable technologies, as rare-earth extraction raises environmental and geopolitical issues. The metastable Fe₁₆N₂ phase has therefore attracted considerable attention due to its high saturation magnetization. However, to compete with rare-earth permanent magnets, shape anisotropy must be induced in the material.

In this context, we investigate the magnetically driven assembly of iron nanoparticles synthesized via organometallic chemistry. Under an alternating magnetic field, these particles can be aligned and undergo hyperthermia. The aim of our project is to use this approach to form anisotropic iron nanorods by triggering the coalescence and nitridation of the nanoparticles through magnetic induction. To achieve this, the superstructures formed by iron nanoparticles under a magnetic field first had to be studied and then controlled.

I will present our progress in the synthesis of iron nanoparticles suitable for rare-earth-free magnet production, as shown by structural (TEM, XRD) and magnetic (VSM) characterizations. Small-Angle X-ray Scattering (SAXS) performed at the SOLEIL synchrotron is used to characterize the super-crystals formed by the iron nanoparticles under a magnetic field, in order to optimize their assembly. The superstructures obtained led us to study the encapsulation of the NPs in organic templates to control their organization. I will also show that this process can be applied to various kinds of amine-capped NPs. Finally, preliminary results on the coalescence and nitridation of iron nanoparticles under magnetic induction will be presented.

In summary, our work furthers the understanding of the different types of superstructures formed by magnetic nanoparticles under an external magnetic field, and proposes a way to restrict these structures to one dimension using organic templates. These results open a route toward controlled anisotropic nanostructures, a key step in the development of sustainable, rare-earth-free permanent magnets.