1. Institute of Materials ScienceKaunas University of Technology K. Baršausko St. 59 Kaunas LT-51423 Lithuania
2. Department of PhysicsFaculty of Mathematics and Natural SciencesKaunas University of Technology Studentų St. 50 Kaunas LT-51368 Lithuania
3. Mads Clausen InstituteUniversity of Southern Denmark Alsion 2 Sønderborg DK-6400 Denmark