Cu nuclear quadrupole resonance measurements have been made on the single ${\mathrm{CuO}}_2$ layer underdoped high temperature superconducting cuprate (HTSC) ${\mathrm{RuSr}}_2{R}_{2-x}{\mathrm{Ce}}_x{\mathrm{Cu}}_2{\mathrm{O}}_{10+\delta }(R=\mathrm{Eu},\mathrm{Gd})$. It is found that the nearly constant superconducting transition temperature for $x=0.6$ and 0.8 can be attributed to a similar hole concentration in the ${\mathrm{CuO}}_2$ planes and the hole concentration is significantly lower for the nonsuperconducting $x=1.0$ sample. Similar to other HTSCs, the ${}^{63}\mathrm{Cu}$ spin-lattice relaxation rate decreases with increasing hole concentration in the ${\mathrm{CuO}}_2$ planes. There is evidence of a spatially inhomogeneous spin fluctuation spectrum that exists even for the superconducting samples. Similar inhomogeneities have been reported in some of the other HTSCs and, hence, the current results provide further evidence of inhomogeneities in the HTSCs.

• Received 27 May 2005

DOI:https://doi.org/10.1103/PhysRevB.73.064510