1. Institut Néel, associé à l’Université Joseph Fourier, CNRS, BP 166, 38042 Grenoble Cedex 9, France
2. CNR-Institute of NanoSciences S3 via Campi 213/a, 41125 Modena, Italy
3. Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany
4. IPCMSCNRS-Université de Strasbourg, 67034 Strasbourg, France
5. CNR-Institute of NanoSciences S3 via Campi 213/a, 41100 Modena, Italy
6. Dipartimento di Fisica, Università di Modena e Reggio Emilia, via Campi 213/a, 41125 Modena, Italy