1. Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
2. Center of Physics and Chemistry of New Materials, Department of Physics, Osnabrück University, Barbarastraße 7, 49076 Osnabrück, Germany
3. Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany