High-temperature superconductivity and antiferromagnetism in multilayer cuprates: 63Cu and 19F NMR on five-layer Ba2Ca4Cu5O10(F,O)2

We report systematic Cu and FNMR measurements of five-layered high-T-c cuprates Ba2Ca4Cu5O10(F,O)(2). It is revealed that antiferromagnetism (AFM) uniformly coexists with superconductivity (SC) in underdoped regions, and that the critical hole density pc for AFM is similar to 0.11 in the five-layered compound. We present the layer-number dependence of AFM and SC phase diagrams in hole-doped cuprates, where p(c) for n-layered compounds p(c) (n) increases from p(c) (1) similar to 0.02 in La2-xSrxCuO4 or p(c) (2) similar to 0.05 in YBa2Cu3O6+y to p(c) (5) similar to 0.11. The variation of p(c) (n) is attributed to interlayer magnetic coupling, which becomes stronger with increasing n. In addition, we focus on the ground-state phase diagram of CuO2 planes, where AFM metallic states in slightly doped Mott insulators change into the uniformly mixed phase of AFM and SC and into simple d-wave SC states. The maximum T-c exists just outside the quantum critical hole density, at which AFM moments on a CuO2 plane collapse at the ground state, indicating an intimate relationship between AFM and SC. These characteristics of the ground state are accounted for by the Mott physics based on the t-J model; the attractive interaction of high-Tc SC, which raises Tc as high as 160 K, is an in-plane superexchange interaction J(in) (similar to 0.12 eV), and the large Jin binds electrons of opposite spins between neighboring sites. It is the Coulomb repulsive interaction U (>6 eV) between Cu-3d electrons that plays a central role in the physics behind high-T-c phenomena.