1. Institute of Physics IA; RWTH Aachen University; 52074 Aachen Germany
2. Peter Grünberg Institute (PGI 10); Forschungszentrum Jülich; 52428 Jülich Germany
3. Department of Engineering; University of Cambridge; Cambridge CB2 1PZ UK
4. Institute of Condensed Matter and Nanosciences; Université Catholique de Louvain; B1348 Louvain-la-Neuve Belgium
5. Centre Interdisciplinaire de Nanoscience de Marseille; CNRS and Aix-Marseille University; Campus de Luminy; Marseille F 13288 Cedex 09 France
6. CESAM & Physics of Solids; Interfaces and Nanostructures; B5, Université de Liège; B4000 Sart-Tilman Belgium
7. UGA; CEA-LETI; MINATEC campus; 17 rue des Martyrs F 38054 Grenoble Cedex 9 France