Modeling strong coupling effects in core-shell nanoparticles: beyond the rigid-coupled model.

D. LAURA-CCAHUANA; E. DE BIASI

Puerto Varas

Workshop; XII Latin American Workshop on Magnetism, Magnetic Materials, & their Applications (LAW3M) 2023; 2023

Universidad Técnica Federico Santa María

In this work we have studied the internal coupling in magnetic nanoparticles withcore-shell structure (antiferromagnet-ferromagnet) performing Monte Carlosimulations based on an atomistic model of the system. In the treatment, differentinternal regions of the particle have been labeled to analyze the magnetic order andthe coupling degree between them. Our results show that it is not always possible toachieve an optimal coupling condition (rigid coupling) between the core and the shellbecause the magnetic order at the interface may be destroyed. This happens when thevalue of interfacial exchange necessary to couple the core and shell generates highlocal fields that magnetically mess up the particle interface. Studying the coercivity asa function of the interfacial exchange (| |), a non-monotonic behavior is observed.The coercive field begins to increase with J_int, and then falls to a minimum beforestarting to grow again. This last behavior is due to the fact that a new and more stable“magnetic order” is generated at the interface. Our study shows that the core-shellcoupling improves the hysteresis of the system and makes it more stable withtemperature (increasing the blocking temperature), consistent with experimentalobservations.