Absence of local moments in superconductor YBa2Cu3O6.95

With the use of spin-polarised neutrons and polarisation analysis the magnetic scattering from the superconducting cuprate YBa2Cu3O6+x (x = 0.95, Tc = 90 K) is measured in the normal state at T = 300 K and placed on an absolute scale with the use of a vanadium standard. These measurements show conclusively that there is negligible magnetic scattering in the normal state below 30 meV. What little scattering is observed corresponds to a paramagnetic scattering cross-section of (0.048 ± 0.008) b or to ∝3.2% of the Cu atoms carrying a spin 1/2. (orig.)