Regensburg 2025 – scientific programme

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MA: Fachverband Magnetismus

MA 38: Magnetic Particles / Clusters & Biomagnetism

MA 38.7: Talk

Thursday, March 20, 2025, 17:00–17:15, H18

Quantum Mechanical Analysis of Complex Ferrimagnetic States in Iron Oxide Nanoparticles — •Valentína Berecová^1,2, Martin Friák¹, Naděžda Pizúrová¹, and Jana Pavlů² — ¹Inst. Phys. Mater., Czech Acad. Sci., Brno, Czech Republic — ²Dept. Chem., Masaryk Uni., Brno, Czech Republic

Maghemite (γ-Fe₂O₃) is a biocompatible ferrimagnetic iron oxide that crystallizes in an inverse spinel lattice and can be viewed as magnetite (Fe₃O₄) with iron vacancies. Iron oxide nanoparticles related to maghemite have numerous applications in the biomedical field thanks to the combination of their magnetic properties, biocompatibility, low cytotoxicity and small size. Density functional theory calculations were employed to examine the local magnetic moments of individual atoms in two maghemite-related nanoparticles. Our calculations for the nanoparticles were inspired by bulk maghemite γ-Fe₂O₃, where tetrahedrally and octahedrally coordinated Fe sublattices have opposing orientations of local magnetic moments. Importantly, our results show that the nanoparticle surfaces create far more complex magnetic states compared to the magnetic ordering found in bulk. These complex magnetic states were described as "nested" ferrimagnetism, which is characterized by local magnetic moments of Fe atoms with mutually opposite orientations appearing even within each of the two (tetrahedral or octahedral) sublattices. Financial support from the Czech Academy of Sciences (Praemium Academiae of M.F.) is gratefully acknowledged. Computational resources were provided by the e-INFRA CZ project and IT4Innovations National Supercomputing Center.

Keywords: iron oxide nanoparticles; magnetism; DFT; ab initio calculations; maghemite