Possibility of Superconductivity Destruction Caused by Neither the Reduction of Hole Concentration nor Impurity Doping

Raman scattering spectra of single crystals of (Eu2/3Ce1/3)2 Ba2/3Eul/3)2Cu3O8+z (Eu-223) and (Er2/3 Ce1/3)2(Ba2/3La1/3)2 Cu3O8+z (ErLa-223) have been measured at room temperature. A peak due to magnon-pair scattering has been observed at 2600 cm−1 in the spectra of semiconducting Eu-223 but not in superconducting Eu-223. The exchange integral is estimated as 960cm−1, which is nearly the same as that of semiconducting YBa2Cu3O6+z. On the other hand, magnon scattering peak has not been seen in the spectra of nonsuperconducting ErLa-223. This fact suggests that sufficient carriers are doped in the Cu-O2 planes in this material though it does not show superconductivity.