CU TL-NMR STUDY ON THE IMPURITY EFFECT FOR TL-BASED HIGH-T-C CUPRATE IN THE OVER-DOPED REGION/

The non-magnetic impurity effect has been investigated by NMR on Zn-do ped TlBa2CaCu2O7+delta belonging to the over-doped region, where the r eduction rate in T-c with Zn-doping was found to be approximately - 2. 3 K/%, much smaller than La1.85Sr0.15CuO4 and YBa2Cu3O7. The temperatu re dependence of the Cu-NMR Knight shift was analyzed with the partial ly closed d-wave model proposed by Ishida et al. to find that the resi dual density of states at the Fermi level increases with the Zn-concen tration. The ratio between the residual density of states and the redu ction rate in T-c was found to be in accordance with the theoretical c alculation in the unitarity limit by Miyake.