1. Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04001 Kosice, Slovakia
2. Biomedical Center Martin, Jessenius Faculty of Medicine in Martin, Comenius University in Bratislava, Mala Hora 4, 03601 Martin, Slovakia
3. Institute of Physics, Faculty of Sciences, Pavol Jozef Safarik University in Kosice, Park Angelinum 9, 04154 Kosice, Slovakia
4. Institute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 04001 Kosice, Slovakia