Higher-harmonic Susceptibilities of Bi-ceramic Superconductors

Abstract

For the study of magnetic properties of sintered high-Tc ceramic superconductors, we measured harmonic ac susceptibilities X_n = X_n' - ix_n" of Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_y immersed in an external field H(t) = H'_dc + H_accos(ωt), where H_dc (≥ 0) is a dc bias field and H_ac (> 0) is an ac field amplitude. Measurements of X_n were carried out for n = 1, 2, 3, 5, 7, 9 and μOH_ac = 0.01-0.1 mT. The fundamental frequency used was 132 Hz. The observed results were analyzed within the construct of the Kim-Anderson model for critical-current density. Similar to our previous work for an YBa₂Cu₃O_y sample with Fe impurities, generation of the higherharmonic susceptibilities seems to arise from the supercurrent according to the same model. Details of the measurement and the analysis are presented.