Ni-impurity effect in high-image cuprates studied by neutron scattering and XAFS spectroscopy Original Research Article

Neutron scattering experiments using La2-xSrxCu1-yNiyO4La2-xSrxCu1-yNiyO4 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 x down to x-yx-y. Polarized XAFS measurements using Ni K -edge probe two types of Ni valence states; Ni2+Ni2+ and Ni(2+α)+Ni(2+α)+. It indicates that a strong hole localization occurs around Ni, resulting in an effective spin-View the MathML source12 value at Ni sites. Therefore, a charge impurity nature of Ni is most likely realized when x⩾yx⩾y.