Anomalous magnetisation of YBCO and BSCCO single crystals

Anomalous magnetization characteristics of YBa/sub 2/Cu/sub 3/O/sub y/ and Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ single crystals and their oxygen vacancy dependences are reported. In these crystals the magnetization exhibits a maximum as a function of the applied field. Significant differences in the anomalous magnetization of the YBCO and BSCCO crystals indicate different origins. Several possible explanations are compared with experimental results. Two kinds of pinning centers with different T/sub c/'s could explain the anomalous magnetization of YBCO, while 2-D pancake vortices matching a 2-D defect structure may account for the BSCCO results.<
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