1. LSPM (CNRS-UPR 3407), Université Paris 13, 99
Avenue Jean-Baptiste Clément, 93430 Villetaneuse, France
2. Center for Superconductivity, Spintronics and Surface Science, Technical University of Cluj-Napoca, Str. Memorandumului No. 28,
RO-400114 Cluj-Napoca, Romania
3. Institut Jean Lamour, CNRS, Université de Nancy, BP 70239, F–54506 Vandœuvre, France