1. Modern Magnetic Systems Department Max Planck Institute for Intelligent Systems 70569 Stuttgart Germany
2. Institute of Applied Physics Karlsruhe Institute of Technology (KIT) 76128 Karlsruhe Germany
3. Helmholtz‐Zentrum Berlin für Materialien und Energie GmbH 12489 Berlin Germany
4. Institute of Applied Physics and Abbe Center of Photonics Friedrich‐Schiller‐University Jena Albert‐Einstein‐Straße 15 07745 Jena Germany
5. Helmholtz‐Institute Jena Fröbelstieg 3 07743 Jena Germany
6. Leibniz Institute of Photonic Technology Albert‐Einstein‐Straße 9 07745 Jena Germany
7. Institute of Nanotechnology Karlsruhe Institute of Technology (KIT) 76021 Karlsruhe Germany
8. Massachusetts Institute of Technology 77 Mass Avenue Cambridge MA 02139 USA