1. Department of Physics, VSB-Technical University of Ostrava, 708 00 Ostrava, Czech Republic
2. CEITEC IPM, Institute of Physics of Materials, AS CR, 616 62 Brno, Czech Republic
3. Faculty of the Environment, University of Jan Evangelista Purkyne, 400 96 Usti nad Labem, Czech Republic
4. Centre of Advanced Innovation Technologies, VSB-Technical University of Ostrava, 708 00 Ostrava, Czech Republic
5. Faculty of Mining and Geology, VSB-Technical University of Ostrava, 708 00 Ostrava, Czech Republic