Zn-Neighbor Cu NQR in Zn-Substituted YBa2Cu3O7-d and YBa2Cu4O8

摘要

We studied local electronic states near Zn in optimally dopedYBa$_2$(Cu$_{1-x}$Zn_x)$_3$O$_{7-\delta}$ and underdopedYBa$_2$(Cu$_{1-x}$Zn_x)$_4$O$_8$ via satellite signals of plane-site Cu(2)nuclear quadrupole resonance (NQR) spectra. From the relative intensity of CuNQR spectra, the satellite signals are assigned to Zn-neighbor Cu NQR lines.The Cu nuclear spin-lattice relaxation time of the satellite signal is shorterthan that of the main signal, which indicates that the magnetic correlation islocally enhanced near Zn both for the underdoped and the optimally dopedsystems. The pure YBa$_2$Cu$_4$O$_8$ is a stoichiometric, homogenous,underdoped electronic system; nevertheless, the Zn-induced inhomogeneousmagnetic response in the CuO$_2$ plane is more marked than that of theoptimally doped YBa$_2$Cu$_3$O$_{7-\delta}$.