1. Peter Grünberg Institute (PGI-6), Jülich Research Centre, 52428 Jülich, Germany
2. Department of Physical Chemistry, University of Innsbruck, 6020 Innsbruck, Austria
3. Institute of Physics, University of Graz, 8010 Graz, Austria
4. Elettra-Sincrotrone Trieste S.C.p.A, Basovizza S.S. 14, Km 163.5, Trieste 34149, Italy
5. Physics Department, University of Trieste, 34127 Trieste, Italy
6. CNR - Istituto Officina dei Materiali (IOM), TASC Laboratory, 34149 Trieste, Italy
7. Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 47048 Duisburg, Germany
8. Department of Physics and Astronomy, UC Davis, Davis, California 95616, United States