NMR study of high-T-c superconductors

Recent NMR study of high-T-C superconductors carried out by Osaka group is reviewed. NQR frequency nu(Q). Knight shift K, T-1 of Cu-63 and O-17 were measured over a wide hole doping range from light- to heavy-doped systems, LSCO, YBCO, HBCCO, BSCCO, TBCCO and TBCO, together with impurity and pressure effect. By analysing nu(Q), K and T-1, the local hole numbers of Cu and O at the CuO2 plane, n(Cu) and n(O) the relative magnitude of the uniform susceptibility, chi(0) and the low-frequency component of the antiferromagnetic spin fluctuations (AFSF), chi(Q)/Gamma (chi(Q) is the staggered susceptibility and Gamma is the characteristic energy of the spin fluctuation at q = 0) are obtained. The relation between n(Cu), n(O) and chi(Q), chi(Q)/Gamma, T-C, etc. were discussed. There are optimum values of n(Cu)/2n(O) and n(Cu) + 2n(O) to give maximum T-C. The NMR results in the superconducting state are well-explained by d-wave pairing model. The result is consistent with the AFSF mediated superconducting model.