Reduction step and quenching of superconductivity in Nd1.85Ce0.15Cu1.01Oy : A Raman scattering study

A. FAINSTEIN; A. SERQUIS; R.G. PREGLIASCO; F. PRADO; A. CANEIRO; S. PIÑOL

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Lugar: New York; Año: 2001 vol. 63 p. 184503 - 184508

1098-0121

The superconducting properties of the electron doped materials L22x(Ce,Th)xCuOy (L5Nd, Sm, Pr, and Eu) are extremely sensitive to small variations of the oxygen content. Superconductivityonly appears in samples that are quenched under slightly reduced atmospheres, at oxygen partial pressuresbelow a critical value corresponding to the CuO-Cu2O equilibrium. We present a detailed Raman scatteringinvestigation of Nd1.85Ce0.15Cu11dOy ceramic and single crystalline samples prepared under controlled oxygencontent above and below this critical oxygen partial pressure. The Raman scattering spectra show that CuOtraces are present in all the samples prepared above the critical partial pressure and discontinuously disappearfor the superconducting compounds. These results suggest that CuO might intergrow with the CuO2 planes inthese compounds leading to a subtle internal strain that quenches the superconducting state.