Coexistence of superconductivity and antiferromagnetism in multilayered high-TcsuperconductorHgBa2Ca4Cu5Oy:Cu-NMR study

We report a coexistence of superconductivity and antiferromagnetism in five-layered compound ${\mathrm{HgBa}}_{2}{\mathrm{Ca}}_{4}{\mathrm{Cu}}_{5}{\mathrm{O}}_{y}$ (Hg-1245) with ${T}_{c}=108\mathrm{K},$ which is composed of two types of ${\mathrm{CuO}}_{2}$ planes in a unit cell; three inner planes (IP's) and two outer planes (OP's). The Cu-NMR study has revealed that the optimally doped OP undergoes a superconducting (SC) transition at ${T}_{c}=108\mathrm{K},$ whereas the three underdoped IP's do an antiferromagnetic (AF) transition below ${T}_{N}\ensuremath{\sim}60\mathrm{K}$ with the Cu moments of $\ensuremath{\sim}(0.3--0.4){\ensuremath{\mu}}_{B}.$ Thus bulk superconductivity with a high value of ${T}_{c}=108\mathrm{K}$ and a static AF ordering at ${T}_{N}=60\mathrm{K}$ are realized in the alternating AF and SC layers. The AF-spin polarization at the IP is found to induce the Cu moments of $\ensuremath{\sim}0.02{\ensuremath{\mu}}_{B}$ at the SC OP, which is the AF proximity effect into the SC OP.