1. Peter Grünberg Institute (PGI-6), Jülich Research Centre, Jülich, Germany
2. Institute of Physics, University of Graz, Graz, Austria
3. Elettra-Sincrotrone Trieste S.C.p.A, Trieste, Italy
4. Physics Department, University of Trieste, Trieste, Italy
5. Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Duisburg, Germany
6. Department of Physics and Astronomy, UC Davis, Davis, CA, USA