No abstract

Both the critical current intensity at zero applied magnetic field Ic(T), from nitrogen temperature up to the critical temperature, and the normal-state resistivity ρn(T) have been measured in granular Bi1.5Pb0.5Sr2Ca2Cu3Oy (BiPbSCCO) superconductors, with different granular characteristics. It is found that the combination [Ic(T)/P][ρn(0)/ρ′n], where ρ(0) is the residual normal-state resistivity, ρ′n is the temperature derivative and P is the sample’s perimeter, is essentially constant from sample to sample at any temperature. It thus constitutes a universal temperature-dependent critical current for the polycrystalline BiPbSCCO family.

A procedure to induce a persistent current in superconducting cylinders or rings was developed using a coil and a ferromagnetic core. Using the field cooling method, the current is induced from the combined effect of the coil magnetic field and the core magnetization. The proposed method was checked using four Bi-2223 samples. The main usefulness seems to be that a high persistent current can be induced using small both probe currents and coils.

No abstract

No abstract