Dissipative behavior and γ-irradiation of silver-sheathed Bi 1.8Pb 0.4Sr 2Ca 2Cu 3O x tape

Abstract

Dissipative mechanisms in Bi 1.8Pb 0.4Sr 2Ca 2Cu 3O x tapes were investigated using magnetoresistance measurements and V– I characteristics. A considerable broadening of the resistive transition in applied magnetic field was observed up to a field of 0.5 T. The temperature and magnetic field dependence of the resistance R( T, B) were fitted to the Arrhenius relation and from which the magnetic field dependence of the pinning energy U 0( B)∼ B − α with α≈0.9 was derived. The variations of the critical current densities J c with temperature and magnetic field before and after γ-irradiation were also studied. The temperature dependence of J c( T) was fitted to the relation J c( T)∼(1− T/ T c) n with n=1.9 and discussed in terms of thermally activated flux flow (TAFF). However, J c( B) results were explained based on the weak links, grain boundaries, and Josephson junctions in which it shows a power law behaviour J c( B)∼ B −0.5. At relatively low temperatures and magnetic fields, the critical current density was increased with a γ-irradiation up to a dose of 100 MR.