Cu NMR study of the pseudogap in Pb2Sr2(Y,Ca)Cu3O8+σ

NMR measurements on ⁶³Cu in underdoped Pb2Sr2(Y,Ca)Cu3O8+σ crystals are reported. A pseudogap is observed in the Knight shift and spin-lattice relaxation rate for the planar ⁶³Cu. In contrast to other underdoped compounds, the pseudogap observed in the Knight shift is weak and occurs at a significantly lower temperature. On the other hand, the effect the pseudogap has on spin-lattice relaxation is quite similar to that in other compounds. The …