1. Institute of Physics, Faculty of Sciences, P.J. Šafárik University, Park Angelinum 9, 041 54 Košice, Slovakia
2. Institute of Chemistry, Faculty of Sciences, P.J. Šafárik University, Moyzesova 11, 041 54 Košice, Slovakia
3. National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310-3706, USA
4. Department of Physics and National High Magnetic Field Laboratory, University of Florida, Gainesville, FL 32611-8440, USA