NMR-STUDY ON LA AND TL-BASED HIGH-T-C CUPRATES

NMR study on three types of high-T-C cuprates TlBa2CaCu2O7+delta (T112 12), La2-xBaxCuO4 (LBCO) and (La1-yYy)(2-x)Ce2CuO4 (LYCCO) is reported . First, the Knight shift in the superconducting state was investigate d for the Zn-substituted TlBa2Ca(Cu1-zZnz)(2)O-7+delta, which belongs to the over-doped region. The temperature dependence of the Knight shi ft was successfully explained in terms of the partially closed d-wave model proposed by Kitaoka et al. The reduction in T-C by Zn-substituti on was also consistent with Miyake's theoretical calculation on the po tential scattering of Next, the impurity effect on the anomalous suppr ession of the superconductivity in La2-xBaxCuO4 (LBCO) around x congru ent to 1/8 was investigated by La-NMR and ultrasonic measurements. The transition temperatures of the magnetic order and of the structural p hase transformation in Zn2+ and Ce4+-doped LBCO have shown that the ma in and direct force to the suppression in the superconductivity is the magnetic ordering, and that the role of the structural phase transfor mation is the enhancement of the suppression. Lastly, the new electron doped cuprate free from 4f-spins has been synthesized and studied by NMR. Observed spectra of (CU)-C-63/65 Without quadrupolar splitting si milar to other conventional electron-doped cuprates indicate that the doped carrier in this system is electron like.