Irreversibility Lines of Rb3C60 Fullerene

M. F. Tai ； M. W. Lee

《Chinese Journal of Physics》 34卷2S期 (1996/04) Pp. 661-664

並列摘要

The irreversibility line H;,,(T) of isotropic superconducting Rb3C60 fullerene (Tc=30.5 ± 0.1 K) was obtained from M(T) curves for low fields and M(H) curves for high fields, respectively. It can be described by a simple power-law equation, Hirr(T) = Hirr(0)[1 - T/T0]^7. Based on experimental data the best fitting results to this scaling relation are determined as: 7 = 2.04±0.16, Hirr(0) = 47.0i5.2 T, and T0 = 30.4±0.2 K for Hirr ≤ I T (T ≤ 0.8Tc); and γ = 1.50 ± 0.03, Hirr(0) = 89.8 ± 1.6 T, and T0 = 30.9 ± 0.4 K for 1 T ≤ Hirr ≤ 5 T (T ＜ 0.2Tc). The characteristic crossoverfield of H～1 T separates the two regions of different γ values. The existence of γ value near 2 suggests that the irreversibility line close to Tc is possibly due to thermally activated vortex-lattice melting that may have occurred in our Rb3C60 sample. The other value of γ = 1.5 may be attributed to a vortex-glass phase transition in low temperatures.