A lead NMR-study of the superconductor Pb 2Sr 0.9La 1.1Cu 2O 6.1

Abstract

Pb 2Sr 0.9La 1.1Cu 2O 6.1 is one of the few high- T c superconductors with a CuO 2-monolayer. Here we report the 207Pb-NMR measurements of the Knight shift and the nuclear spin-lattice and spin-spin relaxation rate on a powder sample with a T c=33 K. As in YBa 2Cu 3O 6.63, the Knight shift, as a function of temperature, starts to decrease below T≈3 T c. The spin-lattice relaxation rate can be modelled quantitatively with the MMP theory. The load oxide layers in the title compound contribute clearly to the metallic nature of the CuO 2-layers. With respect to the quasi particle contributions, the antiferromagnetic correlations are of less importance to the spin-lattice relaxation in the lead cuprate as compared to e.g. YBa 2Cu 3O 6+δ and La 1.85Sr 0.15CuO 4. The relative contribution of the antiferromagnetic part to the static susceptibility is about 3% (β=0.5), while the antiferromagnetic correlation lengths extracted from the MMP theory are comparable to those of La 1.85Sr 0.15CuO 4.