a Korea Research Institute of Standards and Science, P.O. Box 102, Yusong, Taejon 305–606, South Korea
b Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba 305, Japan
Abstract:
We have observed the anomalous magnetization of Bi2Sr2CaCu2−xNixO8 (x = 0 and 0.02) single crystals. Anisotropy decreases with iodine intercalation although it expands the space between CuO2 layers. Iodine intercalation seems to suppress the magnetization anomaly for Ni = 1% crystals, but not for Ni = 1% substituted crystals. We have discussed these results in terms of the increase of anisotropy by Ni substitution and the dimensional crossover of flux lines. Effects of both oxygen concentration and substitution of a magnetic element for the Cu site on the anisotropy of Bi2Sr2CaCu2O8 crystals show the same tendency as the case of the YBa2Cu3O7 superconductor.