1. School of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
2. Magnetic Nanostructure Characterization: Technology and Applications, CIRI-AUTH, Thessaloniki 57001, Greece
3. Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Duisburg 47048, Germany