Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 56: Metal substrates: Adsorption of organic / bio molecules III
O 56.8: Vortrag
Mittwoch, 28. März 2012, 18:30–18:45, A 053
Tuning the electronic and magnetic properties of adsorbed Co porphyrin molecules by NO as an axial ligand — •Christian Felix Hermanns, Matthias Bernien, Alex Krüger, Jorge Miguel, and Wolfgang Kuch — Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
Metalloporphyrin molecules consist of a metal ion, surrounded by a planar porphyrin ligand and two axial coordination sites, which can be occupied by additional ligands like small molecules or a metal surface. This allows to tune the electronic and magnetic properties of the ion.
Here, we report on X-ray absorption spectroscopy (XAS) measurements of submonolayers of Co octaethylporphyrin (CoOEP) molecules and NO-CoOEP nitrosyl complexes on bare and oxygen-covered Ni films grown on Cu(100). Angle-dependent N K edge XAS measurements reveal a quasi-flat adsorption of CoOEP on both substrates.
By means of Co L3,2 X-ray magnetic circular dichroism (XMCD) spectra we demonstrate, how the ferromagnetic substrate, as an additional ligand to the CoOEP molecules, induces a magnetic ordering on the spins of the Co ions, which are on both substrates parallel aligned to the Ni magnetization. The adsorption and thermal desorption of NO, as second axial ligand to CoOEP enables the reversible switching of the electronic properties of the Co ions on the oxygen-covered Ni films. On both substrates, angle-dependent Co L2,3 XAS measurements reveal different oxidation states of the Co ions of CoOEP and NO-CoOEP.
This work is supported by the DFG (Sfb 658).