Zn-neighbor Cu NQR in Zn-substituted YBa₂Cu₃O_7-δ and YBa₂Cu₄O₈

We studied local electronic states near. Zn in optimally doped YBa₂(Cu_1-xZn_x) ₃O_7-δ and underdoped YBa₂(Cu_1-xZn_x)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 spin-lattice 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.