1. CIC nanoGUNE, E-20018 Donostia-San Sebastian, Spain
2. IMM-Instituto
de Microelectrónica de Madrid (CNM-CSISC), Isaac Newton 8, PTM, Tres Cantos, E-28760 Madrid, Spain
3. Departamento
de Física Teórica de la Materia Condensada and Condensed
Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
4. Information
Storage Materials Laboratory, Department of Electrical and Computer
Engineering, National University of Singapore, 117576 Singapore, Singapore
5. IKERBASQUE, Basque Foundation
for Science, E-48011 Bilbao, Spain