Magnetoresistance and Irreversibility Fields of Bismuth-Based 1G Tape

The magnetoresistance and irreversibility fields of commercial bismuth-based 1G tape were studied on the basis of the temperature dependencies of the magnetoresistance at the two relative orientations of magnetic field and superconductor plane. The critical temperatures of this tape are the following: T _{c50 %} = 110.3 K and T _c0 = 109.9 K, and the width of superconducting transition is ΔT = 0.5 K. The widths of the transition to the superconducting state versus applied magnetic fields were derived for both orientations. The experimental data were fitted using the formula ΔT = C H ^m + ΔT ₀. The irreversibility field values were obtained and successfully fitted as a function of temperature. At 77 K, they were found to amount to H _{i r r} = 72.8 kOe and H _{i r r} = 5.5 kOe for the parallel and perpendicular directions, respectively.