SUPPRESSION OF THE SUPERCONDUCTING GAP AND THE SPIN-FLUCTUATION GAP OF YBA2CU3OY (Y=7.0 AND 6.76) BY ZN SUBSTITUTION AS MEASURED BY GD3+ ELECTRON-SPIN-RESONANCE

The local susceptibility around Zn atoms in Gd-doped YBa2(Cu0.97Zn0.03)3Oy has been measured by the electron-spin-resonance Knight shift of Gd3+ at 245 GHz. The magnitude and distribution of the shifts are compared with the corresponding data for compounds with no Zn. For both y = 7. 0 and 6.76 the full density of states (corresponding to the high-temperature normal state of the pure y = 7.0 compound) is restored at the first-neighbor sites of Zn atoms irrespective of whether the material is superconducting or not. This shows that both the superconducting gap and the spin-fluctuation gap are locally suppressed by Zn substitution.