1. Institute of Physics, Chemnitz University of Technology, 09107 Chemnitz, Germany
2. Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany
3. Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
4. Institute of Experimental Physics of Functional Spin Systems, Technical University Munich, James-Franck-Str. 1, 85748 Garching b. München, Germany
5. Institute of Physics, University of Augsburg, Universitätsstraße 1, 86159 Augsburg, Germany