Rare-earth dependence of photoinduced chain-oxygen ordering in R Ba2Cu3O7-x (x0.3) investigated by Raman scattering

We investigated a set of oxygen-deficient R Ba 2 Cu 3 O 7 - x (x0.3) ceramic samples with Raman spectroscopy under resonant conditions for the defect-induced Cu-O chain related modes at 230 and 600 cm - 1 . Emphasis was laidon 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=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 β = 0.36′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.