Fundamental and harmonic susceptibilities of an oxide superconductor synthesized by the polymerized complex method

To examine the utility of the Kim-Anderson model for the study of the magnetic response of ceramic superconductors, we measured ac complex susceptibilities χ_n = χ_n ^′ - iχ_n ^″ (n = 1, 2, 3) of an oxide superconductor YBa₂Cu_2.95Co_0.05O_y synthesized by the polymerized complex method, and attempted to simulate the results in the framework of this model. Analyses of χ_n have shown that generation of the harmonic susceptibilities can be reproduced pretty well by the model, where the material parameters k and B₀ involved were determined so as to give the best fit to the observed χ_n. Comparison of k which corresponds to the pinning force against a flux quantum with those obtained for other ceramic specimens prepared by other methods have revealed that k well reflects the sample quality in view of critical current density.