Inelastic neutron scattering measurements have been performed, for the firs
t time, on a large, high quality single-crystal of PrBa2Cu3O6+x. Two relati
vely broad peaks are observed, the one at lower energy showing significant
dispersion in the basal plane. Neither feature is observable above the Pr o
rdering temperature. The pressure dependence of the Cu and Pr ordering temp
eratures up to 1.75 GPa has also been determined. (C) 1999 Elsevier Science
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