We investigated a set of oxygen-deficient $R{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-x}$ $(x\approx 0.3)$ ceramic samples with Raman spectroscopy under resonant conditions for the defect-induced Cu-O chain related modes at 230 and 600 ${\mathrm{cm}}^{\mathrm{-}1}$. Emphasis was laid on the frequency and intensity of the modes for different rare-earth atoms, and especially on their dependence under illumination. The modes display photoinduced bleaching for all R, including the nonsuperconducting $R=\mathrm{Pr}.$ The dynamics of their bleaching following a temperature quench indicates similar complex relaxation processes for all samples. A simple stretched exponential with a common $\beta =0.36\mathrm{}\pm 0.04$ and a distribution of time constants ranging from 50 to 1400 s describes our data well. We discuss our results in connection to photoinduced chain-oxygen ordering in oxygen-deficient superconductors.

• Received 17 August 2001

DOI:https://doi.org/10.1103/PhysRevB.65.024522