Regensburg 2022 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 39: Magnetic Particles / Clusters

MA 39.3: Vortrag

Freitag, 9. September 2022, 10:00–10:15, H47

Structural, chemical and magnetic properties of iron-oxide core-shell nanocubes — •Aladin Ullrich, Michael Kühn, and Manfred Albrecht — Institut für Physik, Universität Augsburg, 86159 Augsburg, Germany

Iron oxide nanoparticles in the size range from 8 to 17 nm were synthesized by thermal decomposition of iron oleate precursor in a high-boiling solvent with Na-oleate as surfactant to produce cubic nanoparticles. The structural composition of the nanoparticles was investigated by transmission electron microscopy and electron energy loss spectroscopy, revealing a core-shell structure with a wustite like structure in the core and a spinel like structure in the shell [1]. Changes in the oxidation state of the iron as well as the core/shell ratio were determined. The core/shell ratio was tuned by successive oxidation until the core had disappeared completely. A sample series consisting of 8 different core/shell ratios was produced during the oxidation process. The magnetic properties of this antiferromagnetic core - ferrimagnetic shell system like exchange bias, coercivity, and blocking behaviour were investigated. With decreasing core/shell ratio the blocking temperature, the coercivity, as well as the exchange anisotropy decreased. Besides this, the influence of the particle size on the magnetic properties was studied as well. Here, for rising particle size an increasing blocking temperature, as well as an increasing exchange anisotropy in the blocked state at low temperatures was found.

[1] A. Ullrich, et al., Sci. Rep. 9, 19264 (2019).