1. Center for Spinelectronic Materials and Devices, Department of Physics; Bielefeld University 33615 Bielefeld Germany
2. Department of Materials; ETH Zürich; Hönggerbergring 64 8093 Zürich Switzerland
3. Departamento de Fisica de la Materia Condensada; Universidad de Zaragoza; 50009 Zaragoza Spain
4. Instituto de Nanociencia de Aragón (INA) &Laboratorio de Microscopías Avanzadas (LMA), Universidad de Zaragoza; 50018 Zaragoza Spain
5. Department of Materials Science and Engineering; Massachusetts Institute of Technology; Cambridge 02139 Massachusetts USA
6. Advanced Light Source; Lawrence Berkeley National Laboratory; Berkeley 94720 California USA
7. Physics of Nanodevices; Zernike Institute for Advanced Materials, University of Groningen; 9747 AG Groningen The Netherlands