On the normal and superconducting properties of Ba6C60

From SQUID measurements we determine the basic critical magnetic field values for bcc phase Ba₆C₆₀ superconductor and hence evaluate the major parameters of superconductivity in this material. A comparative analyses of these parameters observed for the alkaline-earth-doped vs. alkali-metal-doped C60 superconductors is presented. These two systems are found to differ substantially in their superconducting properties: for Ba₆C₆₀ we find that the upper critical fieldH _c 22 T, and the Ginzburg-Landau parameter15, as compared to the values 50 T and 100, respectively, for superconducting K₃C₆₀. On the other hand, the electronic properties for all the superconducting fullerenes are rather similar with, for example, the Fermi energyE _F0.1 eV.