NMR Study of High-TC Superconductors

Abstract Recent NMR study of high- T c superconductors carried out by Osaka group is reviewed. NQR frequency v Q , Knight shift K , T 1 of 63 Cu and 17 O 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 v Q , K and T 1 , the local hole numbers of Cu and O at the CuO 2 plane, n (Cu) and n (O) the relative magnitude of the uniform susceptibility, χ 0 and the low-frequency component of the antiferromagnetic spin fluctuations (AFSF), χ Q / Γ ( χ Q is the staggered susceptibility and Γ is the characteristic energy of the spin fluctuation at q = 0) are obtained. The relation between n (Cu) n (O) and χ Q , χ Q / Γ , Γ C etc. were discussed. There are optimum values of n (Cu)/2 n (O) and n (Cu) + 2 n (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.