High-Field Critical Current Properties of (Bi, Pb)₂Sr₂Ca₂Cu₃O_yFilaments

To understand the temperature, magnetic field, and angular dependence of the critical current density, Jc(T, B, θ), of (Bi, Pb)2Sr2Ca2Cu3Oy (Bi2223) core composed of commercial Bi2223 tapes, we investigated Jc(T, B, θ) of a bundle of Bi2223 filaments extracted from Ag-sheathed Bi2223 tapes under broad (T, B, θ) conditions. We found that flux pinning curves for B||c (θ = 0°) exhibit a temperature-scaling relation at high T (50-77.3 K) but not at low T (30-40 K). We also found that Jc(θ) exhibits a broad peak in the B||ab (θ = 90°) direction and attributed it to the broadening of a sharp peak due to the intrinsic pin caused by a c-axis misalignment. We plotted Jc(T, B, θ) as a function of the tape normal component of the magnetic field considering the c-axis misalignment, and it agrees well with the measured Jc(T, B, 0°). This indicates that the intrinsic pinning is strong in Bi2223 and Jc(θ) of Bi2223 is dominated by the flux pinning for the B||c component. Based on these findings, we succeeded in reproducing Jc(T, B, θ) at 50-77.3 K by a model taking account of the T-scaling law, c-axis misalignment, and intrinsic pinning.