  Neutron scattering experiments have been carried out to explore Ni-impurity
effects on static spin correlations in La2-xSrxCuO4 (LSCO) in the vicinity of
the superconductor-insulator boundary where both parallel and diagonal
spin-density modulations (SDM) coexist at low temperature. Upon dilute Ni
substitution the incommensurability decreases for both types of SDM, while the
volume fraction of the diagonal (parallel) SDM increases (decreases).
Subsequent Ni doping induces a bulk three-dimensional antiferromagnetic (AF)
order when x ~ Ni concentration. TN of such the AF order depends on x and seems
to disappear at x ~ 0.1. These effects are approximately ascribed by a
reduction of mobile holes, and by a transition from the parallel to the
diagonal SDM induced by Ni.
