High-energy Cu spin excitations in PrBa2Cu3O6+x

This paper describes high-energy neutron inelastic scattering measurements of propagating magnetic excitations in PrBa2Cu3O6+x (x � 0.2 and 0.93). The measurements probe the acoustic and optic modes of the antiferromagnetically-ordered copper–oxygen bilayers in the energy range 50– 150meV. The observed magnon dispersion can be described satisfactorily in this energy range by a spin wave model including intra- and inter-layer nearest-neighbour exchange constants Jk and J⊥. We find Jk = 127 ± 10meV and J⊥ = 5.5 ± 0.9meV. The value of Jk is virtually the same as that found in YBa2Cu3O6.2, but J⊥ is a factor of two smaller. To within experimental error the values of Jk and J⊥ for PrBa2Cu3O6+x do not vary with oxygen doping.