1. Instituto de Física, Facultad de Ingeniería, Universidad de la República, Herrera y Reissig 565, C.C. 30, 11000 Montevideo, Uruguay
2. Swiss Federal Laboratories for Materials Science and Technology (Empa), Überlandstrasse 129, 8600 Dübendorf, Switzerland
3. Institute of Solid State Physics of the Russian Academy of Sciences, 142432 Chernogolovka, Russian Federation