1. 2nd Institute of Physics and JARA-FIT, RWTH Aachen University, 52074 Aachen, Germany
2. Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
3. International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
4. Peter Grünberg Institute (PGI-9) Forschungszentrum Jülich, 52425 Jülich, Germany