Influence of thermal scanning and local inhomogeneity on the shape of AC susceptibility curves of high-TC superconductors

The effects of the temperature gradient (p) and heat transfer’s velocity (q) parameters on the shape of AC susceptibility curves were experimentally explored. At homogeneous Y1.01Ba1.95Cu2.97O6.86 ceramic samples only broadening with negligible horizontal translation and shape distortions of the χ′ and χ″ susceptibility curves were observed. At samples with local inhomogeneity—beside broadening—a proportional peak-deep-hump type distortion and horizontal translation of the χ″, and rotational translation of the χ′ curves appeared. The results—leading to a clearer understanding of how inhomogeneities and the scanning parameters influence the shape of the AC susceptibility curves—allow separating the effects of local inhomogeneities from the ones produced by structural modifications. It is confirmed that the spatial resolution of the method for local inhomogeneities is proportional to p and inversely proportional to q until a limit is determined mainly by the relaxation time of the studied phenomenon.