1. Institute of Physics, Cracow Technical University, Podchorążych 1, 30-074 Kraków, Poland
2. Institute of Physics, Jagiellonian University, Reymonta 4, 30-59 Kraków, Poland
3. W. Trzebiatowski Institute of Low Temperatures and Structure Research, Polish Academy of Sciences, Okólna 2, 50-950 Wrocław, Poland