Flux-lattice melting and flux creep in a high-Tcsuperconductor

Abstract
The authors report measurements of the magnetisation-derived critical current jc in TlBa2Ca3Cu4Ox a 122 K superconductor. Analysis of the field H*c2, at which jc scales to zero, naturally falls into two regimes: a low-temperature regime, which can be described by flux-lattice melting, and a high-temperature regime dominated by flux creep. In the latter regime, the scaling of both H*c2 and the sample resistivity with temperature are in good agreement with a model proposed by Tinkham, when anisotropy effects are taken into account. From the former regime, they infer Hc2//(T=0) approximately=430 T.