Neutron scattering studies of vibrational spectra in high-Tc superconductors

The influence of doping Ca and Ba atoms on the vibrational spectrum of La2CuO4 and that of oxygen deficiency on the vibrational spectrum and partial density of Cu atom vibrational states for YBa2Cu3O7-y have been investigated. It is shown that for low concentrations of the doping atoms (x ≤ 0.1) a softening of the high-energy part of the spectrum in La2CuO4 is observed. The oxygen deficiency in YBa2Cu3O7-y is accompanied by softening of the low-energy part of the spectrum and by hardening of the high-energy part of the spectrum. The partial density of the Cu-atom vibrational states ranges up to 40 meV. In transition to a semiconducting state, the partial density is softened