1. Centro S3, Istituto Nanoscienze—CNR, via Campi 213/a, 41125 Modena, Italy
2. Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9, France
3. Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany
4. IPCMS CNRS—Université de Strasbourg, 67034 Strasbourg, France
5. Dipartimento di Fisica, Università di Modena e Reggio Emilia, via Campi 213/a, 41125 Modena, Italy