Cerium-doping and oxygen-reduction effects on magnons and phonons in Nd2−xCexCuO4−y

Abstract

Cerium-substitution and oxygen-reduction effects on magnons in ${\mathrm{Nd}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Ce}}_{\mathit{x}}$ ${\mathrm{CuO}}_{4\mathrm{-}\mathit{y}}$ were investigated by Raman scattering. Even with increasing Ce concentration, the local antiferromagnetic order does not decrease and, moreover, the average energy of the magnon peak increases, in contrast to hole-type superconductors. This quite different behavior between electron- and hole-type superconductors may suggest that the spins do not directly contribute to the superconductive mechanism. Only near x=0.15 is there almost no oxygen deficiency on the ${\mathrm{CuO}}_2$ layers. It indicates that the defects on the layers disturb the superconductivity.