1. Institute of Experimental Physics, University of Wrocław, Max Born Sq. 9, 50-204 Wrocław, Poland
2. Institute of Low Temperature and Structure Research, Polish Academy of Sciences, PO Box 937, 50-950 Wrocław, Poland
3. Institute of Inorganic Chemical Technology, Technical University of Szczecin, Pułaskiego 10, 70-322 Szczecin, Poland