Superconductivity of CaxC60 prepared by thermal decomposition of azide: ESR and LFS microwave absorption study

Summary form only given. We have prepared C/sub ax/C/sub 60/ by thermal decomposition of CaN6 and studied the X-evolution of its superconducting properties by low field (LFS) microwave absorption and conventional ESR. Superconducting phase is found at x=5 and also x=6 (with lower fraction) with Tc = 8.4-8.8K. The results of the annealing at different temperature (300-450 /spl deg/C) and of aging effect on the intensity of LFS (and hence the amount of superconducting fraction) and ESR g-value and linewidths are presented. Preliminary results on the C/sub 13/ isotope effect on superconducting T/sub c/ in C/sub a5/C/sub 60/ are also discussed.