Talk (non-conference) (Invited)

FZJ-2025-03800

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Dynamic Magnetic Structural Properties of FeO𝑥 Nanoparticles as Dispersion

Lin, Y.FZJ*

2025

Abstract: Magnetic nanoparticles (MNPs) exhibit unique size-dependent magnetic and structural behaviors that are strongly influenced by their environment. In this work, we focus on 15 nm FeOx nanoparticles due to their chemical stability and tunable magnetic properties. Using SQUID and PPMS measurements, we investigated their magnetic dynamics through hysteresis loops, ZFC/FC magnetization, AC susceptibility, and relaxation experiments. These techniques allowed us to determine the blocking temperature and to distinguish between Néel and Brownian relaxation mechanisms. Structural responses were studied by SAXS and DLS under different solvents and external magnetic fields. We observed that solvent viscosity plays a critical role in relaxation behavior, with Brownian relaxation dominating at high temperatures in low-viscosity solvents. Moreover, field-dependent SAXS revealed anisotropic scattering patterns, consistent with particle assembly. Model fitting provided quantitative insights into particle size, interaction strength, and field-induced aggregation. Together, these results advance our understanding of how solvent-mediated interactions and external fields couple the magnetic and structural dynamics of FeOx nanoparticles, with implications for biomedical and soft-matter applications.

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Contributing Institute(s):

1. Streumethoden (JCNS-2)
2. JARA-FIT (JARA-FIT)

Research Program(s):

1. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)
2. 6G4 - Jülich Centre for Neutron Research (JCNS) (FZJ) (POF4-6G4) (POF4-6G4)

Appears in the scientific report 2025

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