1. Research Center Jülich, Peter Grünberg Institut, Electronic Materials (PGI-7), 52425 Jülich, Germany
2. SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom
3. Institute of Inorganic Chemistry (IAC), RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany