Superconducting characteristics of M3C60 (M=K, Rb) under magnetic field

The Ginzburg-Landau coherence lengths were evaluated for C 60 -based superconductors by fitting measured magnetization data with the renormalization theory of the fluctuation. The derived coherence lengths are 21±1 and 13±1 A for K 3 C 60 and Rb 3 C 60 , respectively, which are preliminary results but are apparently smaller than the reported values obtained from H c2 (0) with mean field theory.