1. Institute of Applied Materials (IAM-WK), Karlsruhe Institute of Technology (KIT), Engelbert-Arnold-Str. 4, D-76131 Karlsruhe, Germany
2. Institute of Materials Physics, Helmholtz-Zentrum Hereon, Max-Planck-Str. 1, D-21502 Geesthacht, Germany
3. Heinz Maier-Leibnitz Center (MLZ), Technical University of Munich, Lichtenberg Str. 1, D-85748 Garching, Germany