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, T-c = 90 K) is measured in the normal state at T = 300 K and pla ced on an absolute scale with the use of a vanadium standard. These me asurements show conclusively that there is negligible magnetic scatter ing in the normal state below 30 meV. What little scattering is observ ed corresponds to a paramagnetic scattering cross-section of (0.048 +/ - 0.008) b or to similar to 3.2% of the Cu atoms carrying a spin 1/2. (C) 1998 Elsevier Science B.V. All rights reserved.