Abstract
Abstract Single crystal Raman spectra of various scattering geometries were obtained from ceramic H1.0YBa2Cu3O6.7 and H1.0GdBa2Cu3Oy using the microprobe technique. Apart from the five prominent Ag Raman lines being characteristic for YBa2Cu3O7, three more lines at 210 cm−1, 248 cm−1 and 610 cm−1 with exact Ag symmetry are observed in H1.0YBa2Cu3O6.7. The lowest frequency extra Raman lines are unambiguously attributed to IR vibrations ofY and Cu(1), respectively. The line at 610 cm−1 arises from oxygen vibrations but can not be conclusively assigned. Hydrogen occupies the interstitial sites around Cu(1) and Cu(2) (within the Y-plane) and perturbs the vibrations of its nearest-neighbours. The experimental results imply that the modes involving otherwise only odd parity vibrations become Raman active under hydrogen doping. The Raman scattering evidence is given that the hydrogen doping decreases the free holes concentration in YBa2Cu3O7−δ.
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