Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 2: Bio- and Molecular Magnetism
MA 2.3: Vortrag
Montag, 22. März 2010, 11:15–11:30, H10
Ultra-low temperature x-ray magnetic circular dichroism of TM-Ni binuclear molecular magnets. — •Karsten Kuepper1, Ulf Wiedwald1, Florian Mögele2, Bernhard Rieger3, and Paul Ziemann1 — 1Institut für Festkörperphysik, Universität Ulm, Albert-Einstein-Allee 11, D-89081 Ulm — 2Institut für Materialien und Katalyse, Universität Ulm, Albert-Einstein-Allee 11, D-89081 Ulm — 3WACKER-Lehrstuhl für Makromolekulare Chemie, Technische Universität München, Lichtenbergstraße 4, 85747 Garching bei München
Molecular magnets display a large variety of new and complex chemical and physical properties. We have investigated three planar TM-Ni-C46H68N2O6 (TM=Mn,Fe,Co) molecules, which show uncompensated magnetic moments [1] by means of ultra-low temperature XMCD. The experiments have been performed at a temperature of 0.6K in order to probe the magnetic ground state properties. For all three complexes we find Ni to be divalent, also Mn and Co are in a 2+ valence state, whereas mainly Fe3+ ions are present in the Fe-Ni molecule. We find different internal magnetic structures. In the Co-Ni molecule the Ni appears to be in a low spin state, thus no dichroic signal is present, whereas Co shows a strong MCD. A similar result is observed for the Mn-Ni complex, only a very small dichroic Ni signal is present. However, for the Fe-Ni complex both, the Fe and Ni spectra are dichroic, revealing a ferromagnetic alignment of the Ni and Fe ions in this molecule.
[1] F. Mögele et al., Langmuir 25, 13606 (2009).