MAGNETIC-FLUX PENETRATION AND CREEP IN BSSCO-2223 COMPOSITE CERAMICS

We have experimentally investigated the magnetic flux penetration thro ugh a Bi-2223 polycrystalline superconductor synthesized by a classica l solid-state reaction method. Electrical resistance, AC susceptibilit y, the Campbell method and magnetic flux waveform recordings have been analysed and compared in order to separate clearly intergrain and int ragrain contributions. The AC susceptibility frequency dependence has been also examined at T = 77 K in a broad field range (0.01 Ge B-AC < 100 G) The activation energy as a function of AC applied magnetic fiel d is found to present a pronounced minimum for an induction (8 G) corr esponding to full magnetic flux penetration through the intergranular matrix.