1. Department of Physics, University of Crete, P. O. Box 2208, 71003 Heraklion, Greece
2. Institute of Electronic Structure and Laser, Foundation for Research and Technology–Hellas, N. Plastira 100, 70013 Heraklion, Greece
3. Max-Planck-Institut für Eisenforschung, Max-Planck-Straße 1, 40237 Düsseldorf, Germany
4. Institute of Nanoscience and Nanotechnology, NCSR Demokritos, Patriarchou Grigoriou and Neapoleos 27, 15310 Aghia Paraskevi, Athens, Greece
5. Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece