Systematic inelastic neutron scattering studies have been performed on La${}_{1.85}$Sr${}_{0.15}$Cu${}_{1-y}$Ni${}_y$O${}_4$ in order to elucidate the microscopic mechanism of magnetic Ni impurity doping effects on spin dynamics and superconductivity. In contrast to Zn doping, which precipitates static or quasistatic spin correlations around dopant, Ni doping remarkably reduces $E_{\mathrm{comme}}$, the minimum energy of the upward branch of the hourglass-shaped magnetic dispersion where a commensurate magnetic peak is observed. Ni doping at $y\sim 0.04$ further reduces $E_{\mathrm{comme}}$ to zero energy and broadens the distribution of $E_{\mathrm{comme}}$, corresponding to the appearance of the normal state at base temperature ($T\sim 4$ K) as well as the broadening of the superconducting transition.

• Received 4 July 2012

DOI:https://doi.org/10.1103/PhysRevB.86.134529