Ni-impurity effect in high- cuprates studied by neutron scattering and XAFS spectroscopy

Hiraka, Haruhiro*; Wakimoto, Shuichi  ; Matsuda, Masaaki; Matsumura, Daiju   ; Nishihata, Yasuo; Mizuki, Junichiro; Yamada, Kazuyoshi*

Neutron scattering experiments using LaSrCuNiO clarified that the parallel spin-density modulations (SDMs) in the superconducting phase are susceptible to Ni, in the same way as the diagonal SDMs in the insulating spin-glass phase. Ni substitution reduces the mobile hole concentration from down to - . Polarized XAFS measurements using Ni -edge probe two types of Ni valence states; Ni and Ni. It indicates that a strong hole localization occurs around Ni, resulting in an effective spin- value at Ni sites. Therefore, a charge impurity nature of Ni is most likely realized when .