Phonon Dispersion Relations in PrBa2Cu3O6+x (x ~ 0.2)

We report measurements of the phonon dispersion relations in non-superconducting, oxygen-deficient PrBa2Cu3O6+x (x ~ 0.2) by inelastic neutron scattering. The data are compared with a model of the lattice dynamics based on a common interaction potential. Good agreement is achieved for all but two phonon branches, which are significantly softer than predicted. These modes are found to arise predominantly from motion of the oxygen ions in the CuO2 planes. Analogous modes in YBa2Cu3O6 are well described by the common interaction potential model.Comment: 4 pages, 3 figures. Minor changes following referees' comment

Magnetic excitations of single-crystal PrBa₂Cu₃O₆_.₂

Measurements of the low-energy magnetic excitations in single-crystal PrBa2Cu3O6.2, and in YBa2Cu3O6.2 for comparison, have been performed using inelastic neutron scattering. An excitation with weak dispersion is seen, which is compared to a spin-wave model based on the lowest lying crystal field levels of the Pr ion, and including the effect of an anisotropic coupling to the Cu magnetic moments, as well as a Pr-Pr exchange interaction. (C) 2000 Elsevier Science B.V. All rights reserved

Dispersive magnetic excitations in non-superconducting PrBa2Cu3O6+x (x approximate to 0.93)

We report preliminary results of a neutron inelastic scattering study of the magnetic excitations in single-crystal PrBa2Cu3O6+x (x approximate to 0.93). The measurements probe (i) the dispersion of the low-energy crystal field levels of the Pr ion in the low-temperature AFIII magnetic phase and (ii) the Cu optic spin wave mode gap in the AFI magnetic phase. We compare the results with previous measurements made when the same crystal was in an oxygen-deficient state, and thus establish the effect of hole doping on the magnetic excitations