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Contributed talk

Discovery and element-specific characterization of new magnetic hybrid systems

Heiko Wende, Universität Duisburg-Essen, Duisburg, Germany

Magnetic hybrid systems offer the possibility to be utilized in future spintronic and storage devices. We create these new hybrid systems by combination of different building blocks, namely magnetic molecules, nanoparticles and ultrathin films. The hybrids are characterized by element-specific techniques such as X-ray absorption spectroscopy and Mössbauer spectroscopy. This allowed for the identification of a magnetic hysteresis of molecular magnets coupled to ferromagnetic films at room temperature [1]. For the understanding of the magnetic coupling, the close collaboration with experts in theory is essential. By means of density functional theory (DFT) the coupling mechanism in this molecular hybrid was revealed [1].

In a different experiment, the modification of the local structure and the correlation to the magnetic properties of FePt nanoparticles embedded in Al was studied. The experimental results from X-ray magnetic circular dichroism investigations together with DFT calculations provided the identification of guidelines for an atomistic design of ultrahard nanomagnets [2]. A more complex non-collinear spin structure was found in BiFeO3 nanoparticles: by Mössbauer spectroscopy we showed that the cycloidal ordering in these particles is temperature-dependent [3].

Finally, the vision to control the magnetic behavior by electric fields advanced our studies of multiferroic nanocomposites. The interplay of ferroelectric and ferrimagnetic behavior in CoFe2O4 nanopillars embedded in a BaTiO3 matrix as controlled by magnetic fields was determined by X-ray linear dichroism studies. We showed that an electric in-plane polarization can be inscribed by magnetic fields and is stable even at magnetic remanence [4].

[1] H. Wende et al., Nature Materials 6, 516 (2007).
[2] C. Antoniak et al., Nature Communications 2, 528 (2011).
[3] J. Landers et al., Nano Letters 14, 6061 (2014).
[4] C. Schmitz-Antoniak et al., Nature Communications 4, 2051 (2013).

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