1. Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, Prague 8 CZ-18221, Czech Republic
2. NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland
3. Czech Technical University, Technická 2, Prague 6 CZ-166 27, Czech Republic
4. Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Trojanova 13, Prague 2 CZ-120 00, Czech Republic
5. Microelectronics and Materials Physics Laboratories, University of Oulu, P.O. Box 4500, FI-90014 Oulun yliopisto, Finland