1. Advanced Materials Metrology and Life Sciences Division, INRiM (Istituto Nazionale di Ricerca Metrologica), Strada delle Cacce 91, 10135Torino, Italy
2. Departament d’Enginyeria Electrònica, Universitat Autònoma de Barcelona (UAB), 08193Cerdanyola del Vallès, Spain
3. JARA─Fundamentals for Future Information Technology, 52425Jülich, Germany
4. Peter-Grünberg-Institut (PGI 7), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, 52425Jülich, Germany
5. Department of Applied Science and Technology, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129Torino, Italy