1. Université Grenoble Alpes; F-38000 Grenoble France
2. CEA; LETI; Minatec Campus; F-38054 Grenoble France
3. Peter Gruenberg Institute; Forschungszentrum Juelich GmbH and JARA-FIT; 52425 Juelich Germany
4. Institute of Electronic Materials; IWE2; RWTH Aachen University; 52056 Aachen Germany
5. Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons; Forschungszentrum Juelich GmbH and RWTH Aachen University; 52425 Juelich Germany