Abstract
A series materials with have been prepared that do not show phase separation and have sharp superconducting transitions for . These samples have been characterized by x-ray-diffraction, resistivity, field-cooled magnetization, and thermogravimetric analysis. Raman spectra have been obtained for the entire series, including the nonsuperconducting regions. The O(4) stretching mode at ∼500 is seen to harden by 15 , while the Cu(2)-O(2,3) out-of-phase bending mode at ∼340 is seen to soften by 40 on going from Y to Pr. These changes fall on a universal curve for the Raman shifts of all the compounds () as a function of the radii of the rare-earth ions. No abrupt changes in the Raman shifts are observed at , where the superconductivity is destroyed.
- Received 27 December 1988
DOI:https://doi.org/10.1103/PhysRevB.39.12383
©1989 American Physical Society