Berlin 2024 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 66: Poster: Nanostructures at Surfaces
O 66.12: Poster
Mittwoch, 20. März 2024, 18:00–20:00, Poster C
Microscopic and Magnetic Analysis of Iron Oxide Core-Shell Nanoparticles with Variable Core/Shell Ratio — •Aladin Ullrich, Michael Kühn, and Manfred Albrecht — Universität Augsburg, Universitätsstr. 1, 86159 Augsburg
Cubic iron oxide nanoparticles of about 15 nm were prepared by thermal decomposition of an iron oleate precursor in 1-Octadecene [1]. From scanning transmission electron microscopy and electron energy loss spectroscopy (EELS) measurements a core-shell composition of the particles was found. The particles show a wustite like structure in the core and a spinel like structure in the shell that is indicated from signatures in the EELS spectra [2]. Both, the position of the Fe L2,3 white lines and the oxygen fingerprint structure were investigated. By successive oxidation of the particles under a controlled atmosphere, the core/shell ratio could be adjusted up to the complete disappearance of the core. The magnetic properties of this antiferromagnetic core - ferrimagnetic shell system were investigated for a sample series with core/shell ratios from about 0.3 to zero. The change of the magnetic properties like the blocking temperature, the coercivity, and the exchange bias field was investigated. Magnetic memory measurements following different protocols show clear memory effects and, hence, indicate the presence of a super spin glass state in the samples.
[1] A. Ullrich, M. M. Rahman, A. Azhar, M. Kühn, M. Albrecht, Nanoprticle Research 24, 183 (2022). [2] A. Ullrich, M. M. Rahman, P. Longo, S. Horn, Scientific Reports 9, 19264 (2019).
Keywords: Core/shell; iron oxide nanoparticles; magnetic properties; EELS