1. Institute of Nano- and Biotechnologies (INB), FH Aachen, Jülich, Germany
2. Peter Grünberg Institute (PGI-8), Forschungszentrum Jülich GmbH, Jülich, Germany
3. Department
of Physics and Astronomy, Catholic University Leuven, Leuven, Belgium
4. Institute
for Materials Research (IMO), Hasselt University, Diepenbeek, Belgium