Ac susceptibility of polycrystalline (Bi-Pb)2223 superconductors

The temperature dependence of ac susceptibility of (Bi-Pb) 2223 polycrystalline samples was measured as a function of frequency and ac field amplitude. Analysis of the temperature dependence of the Ac susceptibility near the transition temperature (Tc) has been done employing Bean's critical state model. The observed variation of intergranular critical current densities (J c) with temperature indicates that the weak links are superconductor-normal metal-superconductor type for this sample. The frequency effect on Ac susceptibility was also measured. As the frequency increases, (Tp) shifts to higher temperatures. This effect can be interpreted in terms of flux creep. The temperature T, and field, Hac, dependence of activation energy obtained from the Arrhenius plot for the frequency (f) and (Tp), can be described as: U(Hac, T)=U0 (1-T/TC) Hac0.18