Magneto-structural characterization of different kinds of magnetic nanoparticles
Artikel i vetenskaplig tidskrift, 2023

Using well-established measurement techniques like transmission electron microscopy (TEM), dynamic light scattering (DLS), small and wide angle X-ray scattering (SAXS, WAXS), susceptometry, and magnetorelaxometry, the distribution of the physical and magnetic size (magnetic moments) and magnetic anisotropy of a variety of structurally different magnetic nanoparticle samples (MNPs) is analyzed and compared. A term which accounts for the presence of weak magnetic areas (WMAs) within the MNPs was introduced to the widespread analysis model for M(H) data, enabling a consistent interpretation of the data in most of the systems. A comparison of the size distributions as obtained for the physical and the magnetic diameter suggests a multidomain structure for three single core systems under investigation, in all probability evoked by the presence of a wustite phase, as identified by WAXS. Analyzing the relationship d < dm < dc between the average single core diameter d, the effective magnetic (domain) size dm and the cluster diameter dc quantitatively, two qualitatively different magnetic structures in multicore MNP (MCMNP) systems were identified: (i) The magnetic moments of single cores within the MCMNP of fluidMAG tend to build flux closure structures, driven by dipole–dipole interaction. (ii) The magnetic behavior of Resovist® was attributed to the presence of domain sizes of about 12 nm within MCMNP, exceeding the single core diameters of 5 nm. Thereby, WAXS revealed a bimodal crystallite size distribution suggesting a crystallite merging process within the MCMNP. The value of the effective magnetic moment of these MCMNP could be explained within the presented “random moment cluster model” (RMCM). We conclude that the combination of physical and magnetic structure parameters obtained from complementary measurement methods allows a reliable assessment of the magnetic structure of single and multicore MNPs.

Weak magnetic area

Magnetic structure

Multi-core magnetic nanoparticles


Physical structure


D. Eberbeck

Physikalisch-Technische Bundesanstalt (PTB)

Stefan Gustafsson

Chalmers, Fysik, CMAL

Eva Olsson

Chalmers, Fysik, Nano- och biofysik

Kai Felix Braun

Wilhelm Büchner University of Applied Sciences

Christian Gollwitzer

Physikalisch-Technische Bundesanstalt (PTB)

Michael Krumrey

Physikalisch-Technische Bundesanstalt (PTB)

Christian Bergemann

Chemicell GmbH

Andrew Wang

Ocean NanoTech, LLC

William W. Yu

Louisiana State University in Shreveport

Harald Kratz

Charité Universitätsmedizin Berlin

Birgit Hankiewicz

Universität Hamburg

Renate Messing

Universität zu Köln

Natalia Steffens

Universität zu Köln

Annette M. Schmidt

Universität zu Köln

Christa Schmidt

Leibniz-Institut Für Photonische Technologien E.V.

Robert Müller

Leibniz-Institut Für Photonische Technologien E.V.

F. Wiekhorst

Physikalisch-Technische Bundesanstalt (PTB)

Journal of Magnetism and Magnetic Materials

0304-8853 (ISSN)

Vol. 583 171031

Nanometrology Standardization Methods for Magnetic Nanoparticles (NANOMAG)

Europeiska kommissionen (EU) (EC/FP7/604448), 2013-11-01 -- 2017-10-31.


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