NMR of high-T-c superconductors

Recent NMR measurements on high-T-c materials by our group are reviewed. St udy of YBa2Cu3O7+Ni has revealed that the attractive force is spin in origi n. Analysis of T-1, the Knight shift K and T-2G in Tl2Ba2Ca2CuO10 (T12223), HgBa2Ca2Cu3O8 (Hg1223), HgBa2Ca3Cu4O10 (Hg1234) and YBa2Cu4O8 (Y1248) supp orts the antiferromagnetic spin fluctuation (AFSF)-mediated-superconductivi ty-model. The temperatures at which a pseudogap starts to open obtained by 1/T1T, dK/dT, photoemission, resistivity and STM all agree with each other in Bi2Sr2CaCu2O8 (Bi2212). The origin of the pseudogap is discussed.