1. Department of Biomedical Engineering and Measurement; Faculty of Mechanical Engineering; Technical University of Kosice; 04200 Kosice Slovakia
2. Department of Condensed Matter Physics, Faculty of Science, Institute of Physics; P. J. Safarik University; Park Angelinum 9 04154 Kosice Slovakia
3. Slovak Academy of Sciences, Institute of Experimental Physics; 04001 Kosice Slovakia
4. Faculty of Science, Center of Low Temperature Physics; University of Pavol Jozef Safarik; Park Angelinum 9 04154 Kosice Slovakia
5. Instituto de Ciencia de Materiales de Madrid, Institute of the Consejo Superior de Investigaciones Cientificas; 28049 Madrid Spain