We studied local electronic states near Zn in optimally doped YBa2(Cu1−xZnx)3O 7−δ and underdoped YBa2(Cu1−xZnx)4O8 via satellite signals of plane-site Cu(2) nuclear quadrupole resonance (NQR) spectra. From the relative intensity of Cu NQR spectra, the satellite signals are assigned to Zn-neighbor Cu NQR lines. The Cu nuclear spinlattice relaxation time of the satellite signal is shorter than that of the main signal, which indicates that the magnetic correlation is locally enhanced near Zn both for the underdoped and the optimally doped systems. The pure YBa2Cu4O8 is a stoichiometric, homogenous, underdoped electronic system; nevertheless, the Zn-induced inhomogeneous magnetic response in the CuO2 plane is more marked than that of the optimally doped YBa2Cu3O 7−δ . 74.25.Nf, 74.72.Bk

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We report 59 Co nuclear quadrupole resonance (NQR) studies of bilayer water intercalated sodium cobalt oxides NaxCoO2·yH2O (BLH) with the superconducting transition temperatures, 2 K < T c ≤ 4.6 K, as well as a magnetic BLH sample without superconductivity. We obtained a magnetic phase diagram of T c and the magnetic ordering temperature T M against the peak frequency ν3 of the 59 Co NQR transition Iz = ±5/2 ↔ ±7/2 and found a dome shape superconducting phase. The 59 Co NQR spectrum of the non-superconducting BLH shows a broadening below T M without the critical divergence of 1/T1 and 1/T2, suggesting an unconventional magnetic ordering. The degree of the enhancement of 1/T1T at low temperatures increases with the increase of ν3 though the optimal ν3 ∼ 12.30 MHz. In the NaxCoO2·yH2O system, the optimal-T c superconductivity emerges close to the magnetic instability. T c is suppressed near the phase boundary at ν3 ∼ 12.50 MHz, which is not a conventional magnetic quantum critical point.