AL NMR PROBE OF LOCAL MOMENTS INDUCED BY AN AL IMPURITY IN HIGH-T-C CUPRATE LA1.85SR0.15CUO4

Al-27 and Cu-63 NMR measurements in 3% Al-doped La1.85Sr0.15CuO4 (LSCO ) have revealed that the T dependences of the Knight shift, K-27(T), a nd the nuclear-spin-lattice relaxation rate, (27)(1/T-1), are dominate d by local moments induced at neighboring Cu sites by the Al impurity. These experiments prove that spin fluctuation of induced moments is m ainly due to the local spin-exchange coupling, J(sd), with conducting holes. This novel T dependence of (27)(1/T-1) has led to a reliable es timation of J(sd) = 0.055 eV, and the extraction of the T-c reduction rate, Delta T-c = 0.62 K/Al% based on the magnetic pair-breaking schem e, which is by more than I order of magnitude smaller than the experim ental value of Delta T-c = 23 K/Al%.