We report a site selective Cu-NMR study on underdoped Hg-based five-layered high-$T_c$ cuprate ${\mathrm{HgBa}}_2{\mathrm{Ca}}_4{\mathrm{Cu}}_5{\mathrm{O}}_{12+\delta }$ with a $T_c=72\mathrm{K}$. Antiferromagnetism (AFM) has been found to take place at $T_{\mathrm{N}}=290\mathrm{K}$, exhibiting a large antiferromagnetic moment of $0.67–0.69{\mu }_{\mathrm{B}}$ at three inner planes (IP). This value is comparable to the values reported for nondoped cuprates, suggesting that the IP may be in a nearly nondoped regime. Most surprisingly, the AFM order is also detected with $M_{\mathrm{AFM}}(\mathrm{OP})=0.1{\mu }_{\mathrm{B}}$ even at two outer planes (OP) that are responsible for the onset of superconductivity (SC). The high-$T_c$ SC at $T_c=72\mathrm{K}$ can uniformly coexist on a microscopic level with the AFM at OP’s. This is the first microscopic evidence for the uniform mixed phase of AFM and SC on a single ${\mathrm{CuO}}_2$ plane in a simple environment without any vortex lattice and/or stripe order.

• Received 30 June 2005

DOI:https://doi.org/10.1103/PhysRevLett.96.087001