SUPERCONDUCTIVITY OF RB2CSC60 - AC RESPONSE AND UPPER CRITICAL-FIELD

Ternary alkali metal doped fullerene samples of the composition Rb2CsC60 were prepared with optimized synthesis conditions. The superconducting transition occurs at T(C) = 32.5 K with a shielding fraction of approximately 72 %. Detailed investigations of the complex susceptibility chi(T) = chi'(T) - ichi''(T) in dependence of different ac and dc magnetic fields are presented. The extrapolation of the upper critical field values B(c2)(T) measured up to 7 T leads to the zero temperature value B(c2)(0) = (50 +/- 3) T and the Ginzburg-Landau coherence length xi(GL) = (25 +/- 1) angstrom. Furthermore the application of Bean's critical state model allows a first estimation of the critical current densities j(c).