The Effect of Magnetic Fields, Temperature and Current on the   Resistivity of Bi-2223 High Temperature Superconductors
  The electrical resistivity of polycrystalline Bi2Sr2Ca2Cu3O10-x (Bi-2223) was measured vs. applied magnetic fields up to 0.45 T, applied currents up to 1 A, and temperature from liquid nitrogen temperature (LN2) to room temperature. In the lowest temperature region, the only truly zero resistivity was observed when the magnetic field was zero; otherwise, a quadratic dependence on the magnetic field occurred. Hysteresis was noted at the higher currents. Current vs. voltage curves in this region revealed a non-ohmic resistivity. In the transition region to the mixed state, indications of negative resistivity and suggestions of a phase change were observed. Arrhenius plots yielded activation energies of around 0.05 eV/molecule. In the mixed state region up to the transition temperature of ~110K, analysis implied that 4 superconducting quantum states exist and that they are cooperatively filled by the superconducting charge carriers. The occupation of the superconducting quantum states is negatively affected by the applied magnetic field and by the applied current. No effect on the polarity or direction of the magnetic field with respect to the direction of the current was observed. 
B. deMayo
cond-mat.supr-con