2 EFFECTS OF IODINE INTERCALATION ON TC IN BI2SR2CA1-XYXCU2O8 - 2-DIMENSIONALITY AND CHARGE-TRANSFER

The effects of stage-1 iodine intercalation on T(c) have been investigated in Bi2Sr2Ca1-xYcCu2O8. The iodine intercalation causes two large effects: one is a change of the two-dimensionality due to an expansion of the crystal along the c-axis, the other is an increase of conducting hole carriers due to charge transfer between intercalated iodine atoms and CuO2 sheets in the host material. For the stage-1 iodine-intercalation compounds, it has been found that the former effect decreases T(c) by about 10 K and that the latter effect shifts the x dependence of T(c) to larger x values by about 0.05 because of the increase of conducting hole carriers by about 0.025 per CuO2 unit. It has been concluded that the decrease in T(c) through iodine intercalation in Bi2Sr2CaCu2O9 is due to both effects.