1. Institute of Inorganic Chemistry, University of Cologne, Greinstrasse 6, D-50939 Cologne, Germany
2. Forschungszentrum Jülich GmbH, Peter Grünberg Institute (PGI-6), D-52425 Jülich, Germany
3. Institute of Materials Physics, Georg-August-University Goettingen, Friedrich-Hund-Platz 1, D-37077 Goettingen, Germany
4. Center for Neutron Science (JCNS-2) and Peter Grünberg Institute (PGI-4), JARA-FIT, Forschungszentrum Jülich, D-52425 Jülich, Germany