AC magnetic susceptibility of Bi2223-system

The AC magnetic susceptibilities χAC of a Bi2223 sintered sample were measured by the Hartshorn bridge method. The linear AC χ0' showed the two-steps behavior at TC1 and TC2, where TC1>TC2. The χ0'-data between TC1 and TC2 has no HAC-dependence and agreed well with those of powder specimen, and they can be regarded as the intragrain magnetic susceptibility. Below the inter-grain transition temperature TC2, the χ0'' showed a positive peak. The temperature dependence of χ0' and χ0'' were analyzed by the Bean's critical-state model. As a result, the temperature dependence of critical current density JC∝(1-T/TC2)β was obtained with β = 2.3-2.6. The non-linear χ2' and χ2'' below TC2 resemble the behaviors derived from the Bean model, but the negative divergence of χ2' may show the evidence of d-wave paring in the present Bi2223-system. (orig.)