1. Department of Chemical and Geological Sciences, University of Cagliari, Cittadella Universitaria S.P. Monserrato Sestu Km 0.700, 09042 Monserrato, Italy
2. Consorzio Interuniversitario Nazionale per La Scienza e Tecnologia Dei Materiali (INSTM), Cagliari Unit, Via Giuseppe Giusti 9, 50121 Firenze, Italy
3. Department of Inorganic Chemistry, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
4. Department of Low Temperature Physics, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague, Czech Republic