NORMAL PHONON OF SUPERCONDUCTING BI2SR2CACU2OY AND BI2SR2CA2CU3OY

Anomalous softening of the Cu-site vibration was observed at the super conducting transition temperature (T(c)) in the Sn-119 Mossbauer spect ra of the YBa2Cu(Sn)3O7-y. On the contrary, only the normal phonon was observed in the Sn-119 Mossbauer spectra of the superconducting Bi2Sr 2CaCu(Sn)2Oy and Bi2Sr2Ca2Cu(Sn)3Oy having T(c)'s of 77 and 108 K, res pectively. This is ascribed to the characteristic feature of the layer structure which has little interaction between the copper planars inv olved with the superconducting transition. The normal phonon is matche d with the theoretical curve of the ''combined Debye and Einstein'' mo del which is usually applied to semiconductor and insulator.