Oxygen isotope effect of high-pressure synthesized (Cu,C)Ba2Ca3Cu4Oγ

The oxygen isotope effect on T-c in a four-CuO2-layer cuprate of (Cu,C)Ba2Ca3Cu4Oy (T-c = 117 K) has been investigated. The isotope-substituted samples of equivalent quality were successfully synthesized under high pressure directly from precursors which were prepared from the oxides obtained by heating metals of Ba, Ca and Cu in oxygen isotope (O-17 and O-18) atmosphere. We concluded that the oxygen isotope effect (T-c similar to M-alpha: M is the oxygen mass) is small but finite (alpha = 0.021 +/- 0.006) in this compound. This result agrees with the previously reported isotope effects in optimally doped cuprates of Y-123 and (Bi,Pb)-2223. (C) 2002 Elsevier Science B.V. All rights reserved.