LOW-FIELD MAGNETIC-RELAXATION OF SUPERCONDUCTING C60RB3

The relaxation of magnetization M in superconducting C60Rb3 have been measured at different temperature ranges in low magnetic fields below T(c) to explore the flux pinning. The measurements were performed with a superconducting quantum interference magnetometer. The applied magn etic field was 300 G - 600 G and the measured time at each temperature was 1 x 10(4) sec. M versus Int shows a linear behavior for t greater -than-or-equal-to 3600 sec. The data were analyzed in the framework of the flux pinning model of Anderson-Kim. The analyses give the activat ion energy of U(5K) almost-equal-to 20 mev and the critical current de nsity based on J(c)T) is-proportional-to [dM/dlnt] x [U/kT] shows J(c) is-proportional-to (1-t)m, with the exponent m almost-equal-to 2.0. T he results are discussed.