1. Department of Physics and Geology, University of Perugia, Via Alessandro Pascoli, 06123 Perugia, Italy
2. Istituto Officina dei Materiali-IOM, National Research Council-CNR, Via Alessandro Pascoli, 06123 Perugia, Italy
3. Institut Max von Laue – Paul Langevin (ILL) 71 avenue des Martyrs, 38042 Grenoble, France
4. Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Elce di Sotto, 6, 06123 Perugia, Italy