A MODEL FOR RUBIDIUM DIFFUSION IN RBXC60 FULLERITES

Superconducting fullerite Rb3C60 synthesized using alkali-metal azides as a source of the alkali metal shows time-dependent development of t he superconducting phase based on electron spin resonance and low-fiel d microwave absorption data. Time dependences of both signals observed for several hours after the synthesis are described by the Avrami dif fusion model assuming the diffusion process Rb + C60 --> Rb3C60. The m odel permits calculation of the Josephson penetration depth as lambda( J) almost-equal-to 1500 angstrom, which is in agreement with other mea surements.