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

中性子散乱とXAFSによる銅酸化物高温超伝導体のNi置換効果の研究

平賀 晴弘*; 脇本 秀一  ; 松田 雅昌; 松村 大樹   ; 西畑 保雄; 水木 純一郎; 山田 和芳*

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 K-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 .