1. Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstraße 12, 8700 Leoben, Austria
2. Department of Materials Science, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstraße 5, 91058 Erlangen, Germany
3. Institute of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria