1. Aarhus University, Department of Physics and Astronomy, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
2. Charles University, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, 18000 Prague 8, Czech Republic
3. Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, 52425 Jülich, Germany
4. Sincrotrone Trieste S.C.p.A., in Area Science Park, Strada Statale 14, km 163.5, I-34149 Basovizza, Trieste, Italy
5. I.O.M.-C.N.R., in Area Science Park, Strada Statale 14, km 163.5, I-34149 Basovizza, Trieste, Italy