Screening of the middle CuO2 layer in Bi1.6Pb0.4Sr2Ca2Cu3O10 determined from Cu NMR.

Abstract

Knight-shift measurements of the $^{63}\mathrm{Cu}$ nuclei in the sandwiching Cu(2)${\mathrm{O}}_{2}$ layers and the middle Cu(1)${\mathrm{O}}_{2}$ layer in the three-layer bismuth oxide superconductor have been performed. Spin-lattice-relaxation measurements reveal a larger spin-fluctuation enhancement at the Cu(1) sites relative to the Cu(2) sites. This and a reduced spin susceptibility in the Cu(1)${\mathrm{O}}_{2}$ layer indicates that the Cu(2)${\mathrm{O}}_{2}$ layers screen the charge transfer from the bismuth bilayer to the Cu(1)${\mathrm{O}}_{2}$ layer. Our results show that the Cu(1)${\mathrm{O}}_{2}$ layer has distinctly different physical properties than the Cu(2)${\mathrm{O}}_{2}$ layer.