1. Center for Spinelectronic Materials and Devices, Physics Department, Bielefeld University, 33615 Bielefeld, Germany
2. University Service Centre for Transmission Electron Microscopy, Vienna University of Technology, Wiedner Hauptstr. 8-10 / E052, 1040 Wien, Austria
3. Institute for Materials Science, Stuttgart University, Heisenbergstrasse 3, 70569 Stuttgart, Germany