We report characterization and detailed magnetization study in fields up to 2 T in the temperature range between 5 and 80 K of Bi 1.6 Pb 0.3 W 0.1 Sr 2 Ca 2 Cu 3 O y (nominal composition pellets). XRD, field-cooled magnetization measurements, and electrical resistance studies showed that the sample consists of a single phase high-Tc (Bi-2223) superconductor in addition to CaWO y-type impurity. An empirical magnetic phase diagram of the superconducting system has been derived. We determined a H*(T) line where Jc becomes zero. In the region with nonzero critical current density, vortex lattice exhibits mainly two types of pinning behaviours, single vortex and collective pinning behaviour, in different field and temperature range. In addition, the temperature dependence of Jc showed an evidence of two types of pinning centres. In low temperatures (<40 K), the pinning centers with low values of activation energy are active whereas in high temperatures (≥40 K), the pinning centers with larger activation energy are active. These results are compared with those of Job & Rosenberg1 on Bi-2223 ceramic samples.
Symmetry and disorder of the vitreous vortex lattice in overdopedBaFe2−xCoxAs2: Indication for strong single-vortex pinning