1. Institute of Physical Chemistry, Justus Liebig University Giessen, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany
2. Center for Materials Research (ZfM), Justus Liebig University Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany
3. Department of Materials and Earth Sciences, Technical University of Darmstadt, Peter-Grünberg-Strasse 2, D-64287 Darmstadt, Germany