1. Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich GmbH, 52428 Jülich, Germany
2. JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, 52074 Aachen, Germany
3. Peter Grünberg Institute (PGI-10), Forschungszentrum Jülich GmbH, 52428 Jülich, Germany
4. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
5. Helmholtz Nano Facility, Forschungszentrum Jülich GmbH, 52428 Jülich, Germany
6. Institute of Integrated Photonics, RWTH Aachen University, 52074 Aachen, Germany