1. Department of Applied
Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
2. Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
3. Beijing Key Lab of Microstructure and Property
of Advanced Materials, Beijing University of Technology, Pingleyuan 100, Beijing 100024, P. R. China
4. Philips Innovation Laboratories Eindhoven, High Tech Campus 11, 5656AE Eindhoven, The Netherlands
5. Peter Gruenberg Institute 9 (PGI 9) and JARA-Fundamentals of Future Information Technologies, Forschungszentrum
Juelich, 52428 Juelich, Germany