title: Dual nature of a Ni dopant in the hole-type La2-xSrxCuO4 cuprate superconductor.
abstract: Local distortions around a Ni dopant in the hole-type La2-xSrxCuO4 superconductor system were studied by x-ray-absorption fine structure (XAFS) using single crystals over a wide hole-doping range. Two distinct interatomic distances between Ni and in-plane oxygen appear in the Ni K-edge extended XAFS. Combined with previous results on hole-localization effects by Ni doping, two types of charge states are strongly indicated for Ni. This duality disqualifies a magnetic-impurity picture for Ni dopant in the superconducting phase of cuprates.
authors.affiliation: Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Hiraka
authors.forename: D
authors.initials: D
authors.lastname: Matsumura
authors.forename: Y
authors.initials: Y
authors.lastname: Nishihata
authors.forename: J
authors.initials: J
authors.lastname: Mizuki
authors.forename: K
authors.initials: K
authors.lastname: Yamada