1. Advanced Microelectronic Center Aachen (AMICA); AMO GmbH, Otto-Blumenthal-Straße 25; 52074 Aachen Germany
2. JARA-FIT and 2nd Institute of Physics; RWTH Aachen University; 52074 Aachen Germany
3. National Institute for Materials Science; 1-1 Namiki 305-0044 Tsukuba Japan
4. Peter Grünberg Institute (PGI-9); Forschungszentrum Jülich; 52425 Jülich Germany