1. Peter Grünberg Institute (PGI 7 & 10) and JARA—Fundamentals in Future Information Technology, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
2. Department of Materials Science and Engineering and Inter-University Semiconductor Research Center, Seoul National University, 151-744 Seoul, Republic of Korea
3. Institute of Materials in Electrical Engineering and Information Technology II, RWTH Aachen University, 52062 Aachen, Germany