29 research outputs found
Hole depletion and localization due to disorder in insulating PrBa2Cu3O7-d: a Compton scattering study
The (mostly) insulating behaviour of PrBa2Cu3O7-d is still unexplained and
even more interesting since the occasional appearance of superconductivity in
this material. Since YBa2Cu3O7-d is nominally iso-structural and always
superconducting, we have measured the electron momentum density in these
materials. We find that they differ in a striking way, the wavefunction
coherence length in PrBa2Cu3O7-d being strongly suppressed. We conclude that Pr
on Ba-site substitution disorder is responsible for the metal-insulator
transition. Preliminary efforts at growth with a method to prevent disorder
yield 90K superconducting PrBa2Cu3O7-d crystallites.Comment: 4 pages, 3 figures, revised version submitted to PR
Out-of-court restructuring versus formal bankruptcy in a non-interventionist bankruptcy setting
Out-of-court restructuring versus formal bankruptcy in a non-interventionist bankruptcy setting
Restricted Distribution of mRNAs Encoding a Sarcoplasmic Reticulum or Transverse Tubule Protein in Skeletal Myofibers
High-energy Cu spin excitations in PrBa<sub>2</sub>Cu<sub>3</sub>O<sub>6+x</sub>
This paper describes high-energy neutron inelastic scattering measurements of
propagating magnetic excitations in PrBa2Cu3O6+x (x approx 0.2 and 0.93). The
measurements probe the acoustic and optic modes of the
antiferromagnetically-ordered copper--oxygen bilayers in the energy range
50-150 meV. 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 J_parallel and J_perp. We find J_parallel
= 127 +/- 10 meV and J_perp = 5.5 +/- 0.9 meV. The value of J_parallel is
virtually the same as that found in YBa2Cu3O6.2, but J_perp is a factor of two
smaller. To within experimental error the values of J_parallel and J_perp for
PrBa2Cu3O6+x do not vary with oxygen doping.Comment: 6 pages, 5 figures. To be published in Phys. Rev.