ac-susceptibility study of the 110-K superconducting phase of Bi-Sr-Ca-Cu-O

Abstract

ac-susceptibility (χ',χ'') measurements as a function of temperature and ac field amplitude have been carried out on cylindrical samples of the 110-K phase of the Bi-Sr-Ca-Cu-O system. The two single-phase samples used for studies were prepared under different experimental conditions with an aim to understand the regimes of validity of Bean's and Kim's critical-state models. Material-dependent parameters such as critical current density as a function of temperature and effective volume fraction of grains, were estimated using these models. Improvements in the critical-current density and intergrain coupling strength were found when a sample was subjected to intermediate cold pressing between sintering. Field variation of intergranular matrix susceptibility of the sintered sample could be fitted well to Kim's model whereas the data on the press sintered sample were in agreement with Bean's model. © 1994 The American Physical Society.