Superconducting: and Magnetic Properties of the 120 K Superconductor T1Ca3Ba2Cu4O11-δ

賴秋助(C. C. Lai) ； 林澤義(T. Y. Lin) ； 李秉政(P. C. Li) ； 何佩君(P. C. Ho) ； 洪正裕(C. Y. Hung) ； 古煥球(H. C. Ku)

《Chinese Journal of Physics》 28卷4期 (1990/08) Pp. 347-354

並列摘要

Superconducting transition temperature T, around 118-123 K was observed for the high Tc single T1-0 layer superconductor T1Ca3Ba2Cu4O11-δ (1324). Magnetic susceptibility measurement in an applied field Ba of 20 G gives a Meissner fraction of -4πχ= 48% at 5 K for field-cooled (FC) sample. Magnetic irreversibility line H*(T) was observed in this system with the power law H*(T)= 3.19(1 - T/Tc)^1.9‘T for Ba ≤ 0.2 T and H*(T)= 25.5(1 - T/Tc)^3.4T for Ba ≤ G 5 T. This irreversibility line may indicate the onset of vortex lattice melting which separate the long range ordered Abrikosov vortex lattice (immobile-flux region) from the short range vortex glass/liquid state (mobile flux). Lower critical field Hcl(T) can be fitted with the formula Hcl(T) = Hcl(0)(1 - T/Tc)^(1/2)“with Hcl(0) ≌ 50 G. Very large upper critical field Hc2(0) = 136 T were derived from initial slope dHc2/dT. From Hcl(0) and H,(O), long penetration depth λ(0) ≌ 3600 A and short coherence length ξ(0) ≌ 12 A were derived. The vortex lattice melting is closely related to the quasi-two-dimensional nature of the system where small cohernece length and high Tc make thermally-assisted melting possible.