Ni-substituted sites and the effect on Cu electron spin dynamics of (formula presented)

We report a Cu nuclear quadrupole resonance experiment on magnetic impurity Ni-substituted (formula presented) The distribution of Ni-substituted sites and its effect on the Cu electron spin dynamics are investigated. Two samples with the same Ni concentration (formula presented) and nearly the same oxygen content but different (formula presented) ‘s were prepared: One is an as-synthesized sample (formula presented) in an oxygen gas (formula presented) and the other is a quenched one (formula presented) in a reduced oxygen atmosphere (formula presented) The plane-site (formula presented) nuclear spin-lattice relaxation for the quenched sample was faster than that for the as-synthesized sample, in contrast to the (formula presented) relaxation that was faster for the as-synthesized sample. This indicates that the density of plane-site Ni(2) is higher in the quenched sample, contrary to the chain-site Ni(1) density, which is lower in the quenched sample. From the analysis in terms of the Ni-induced nuclear spin-lattice relaxation, we suggest that the primary origin of suppression of (formula presented) is associated with the nonmagnetic depairing effect of the plane-site Ni(2).