1. Institute of Physics, University of Rzeszów, Rejtana 16a, 35-310 Rzeszów, Poland
2. Institute of Physics and Chemistry of Solid States, Uzhgorod National University, Uzhgorod, Ukraine
3. Institute of High Pressure Physics "Unipress", Polish Academy of Sciences, Warsaw, Poland
4. Taras Shevchenko Kiev University, Physics Department, Kiev, Ukraine