Elin L. Winkler
Resonancias Magnéticas, Centro Atómico Bariloche
Instituto de Nanociencia y Nanotecnología, CNEA/CONICET, S. C. de Bariloche (RN), Argentina

One of the main challenges driving the development of nanostructured magnetic materials is the modulation of the magnetization reversion curve. The coercive field, exchange bias field, and saturation magnetization determine their application range, which varies for uses in biomedicine, or magnetoelectronics. These parameters can be tailored by combining compounds with distinct magnetic properties at the nanoscale. Specifically, onion-like architectures enable the integration of different components within a single nanoparticle, offering controlled size and high-quality interfaces, thus expanding application possibilities.
We present different strategies for designing and fabricating magnetic nanoparticles (NPs) with onion-like architectures to tune magnetic anisotropy and magnetic coupling between different phases within a single nanoparticle. For example, in Fe₃O₄/Co_1-xZn_xFe₂O₄ core/shell nanoparticles, the coercivity field can be adjusted by changing the shell’s composition. Additionally, introducing a diamagnetic insulator between the ferrimagnetic phases in Fe₃O₄/MgO/CoFe₂O₄ trilayer system, further modulation of magnetic coupling it is allowed. Moreover, controlled oxidation can tune the exchange bias effect in antiferromagnetic-FeO/ferrimagnetic-Fe₃O₄ core/shell nanoparticles. In these systems we analyze the nanoscale complexities that sometimes result in unpredictable behaviors, posing challenges in the design.
Finally, we explore how the distinct functionalities of the core and shell can be harnessed to enhance the performance of these materials for various applications.