We have investigated the stage-1 iodine-intercalation compounds, whose host materials are Bi2Sr2Ca1-xYxCu2O8 (Bi-2212 phase) and Bi1.6Pb0.5Sr1.9-xLaxCu1.05O6 (Bi-2201 phase) with various x values. In the Bi-2212 phase, it has been found that the change in Tc through the stage-1 iodine intercalation is due to two effects; a change of the two-dimensionality and an increase in the carrier number. The former effect decreases Tc by about 10 K independent of the carrier number of the host sample. The latter effect shifts the x dependence of Tc to larger x values by about 0.08, taking account of oxygen release from the host samples during the intercalation process. This result is clear evidence for the occurrence of both the change of two-dimensionality and the increase in carrier number about 0.04 per CuO2 unit due to the charge transfer through the stage-1 iodine intercalation. In the Bi-2201 phase, Tc decreases by about 10 K through the stage-1 iodine intercalation.
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