Dependence of the phonon state density of the ceramic YBa2Cu3x on the oxygen concentration and temperature
Natkanets I. , Belushkin A. V., Goremychkin E. A., Mater Ya., Sashin I. L., Fedotov V. K., Nikolaev R. K., Ponyatovskii E. G., Sidorov N. S.
The inelastic neutron scattering and neutron diffraction spectra of the compounds YBa2Cu3Ox with oxygen concentrations χ = 6.95, 6.45, and 6.15 at temperatures of290,80, and 10 К have been studied. The generalized phonon state density functions have been obtained. These functions change considerably over a broad energy range (10-90 meV) with increasing oxygen deficiency. As the temperature is lowered, the superconducting samples (x = 6.95 and 6.45) exhibit an anomalous increase in the state density in the energy region 15-40 meV. This effect is absent in nonsuperconducting samples (x = 6.15).