Raman measurements of Y_1-xEu_xBa₂Cu₃O₇: Comparison with Y_1-xPr_xBa₂Cu₃O₇

We present polarized Raman measurements of small single crystals embedded in Y1-xEuxBa2Cu3O7 polycrystalline pellets. Superconductivity remains unsuppressed through the entire range of x. With increasing x, the frequency increase of the Ba-Ba vibrational mode and the apical oxygen Oz-Oz vibrational mode, is significantly smaller than in Y1-xPrxBa2 Cu3O7, even though similar changes in interatomic distances occur in both systems. These results support the assertion that the frequency changes of Ba-Ba and Oz-Oz modes are due to changes in electronic states and not due to interatomic distances. © 1990.