Flux-Line-Lattice Melting and Upper Critical Field of Bi1.65Pb0.35Sr2Ca2Cu3O10+δ Ceramic Samples

Abstract

We have conducted magnetoresistance measurements ρ (T , H ) in applied magnetic fields up to 18 T in Bi 1.65 Pb 0.35 Sr 2 Ca 2 Cu 3 O 10+δ ceramic samples which were subjected to different uniaxial compacting pressures. The anisotropic upper critical fields H c2 (T ) were extracted from the ρ(T , H ) data, yielding H ab c2 (0) ∼ 130 T and the out-ofplane superconducting coherence length ξ c (0) ∼ 3 Å. We have also estimated H c c2 (0) ∼ 4.4 T and ξ ab (0) ∼90 Å. In addition to this, a flux-line-lattice (FLL) melting temperature T m has been identified as a second peak in the derivative of the magnetoresistance dρ/dT data close to the superconducting transition temperature. An H m vs. T phase diagram was constructed and the FLL boundary lines were found to obey a temperature dependence H m ∝ (T c /T − 1) α , where α ∼ 2 for the sample subjected to the higher compacting pressure. A reasonable value of the Lindemann parameter c L ∼ 0.29 has been found for all samples studied.

Temperature- and field-dependent critical currents in [(Bi,Pb)2Sr2Ca2Cu3Ox]0.07(La0.7Sr0.3MnO3)0.03 thick films grown on LaAlO3 substrates

“…7 in-plane [n ab (0)] superconducting coherence lengths amount to $3 Å and $ 90 Å , respectively. 8,9 In turn, the in-plane penetration depth k ab (0) $ 1240 Å , H c2(c) % 4.4 T, and H c2(ab) % 130 T. In superconductor (SC)/ferromagnet (FM) hybrid structures may exist regions where the magnetic field is inhomogeneous. Such inhomogeneous distribution of the magnetic field into the superconductor may pin the vortices and lead to dramatic changes in its electrical and magnetic properties.…”