We report comparative substitution effects of nonmagnetic Ti^(4+) and
magnetic Ir^(4+) impurities for Ru^(4+) in the spin-triplet superconductor
Sr2RuO4. We found that both impurities suppress the superconductivity
completely at a concentration of approximately 0.15%, reflecting the high
sensitivity to translational symmetry breaking in Sr2RuO4. In addition, a rapid
enhancement of residual resistivity is in quantitative agreement with
unitarity-limit scattering. Our result suggests that both nonmagnetic and
magnetic impurities in Sr2RuO4 act as strong potential scatterers, similar to
the nonmagnetic Zn^(2+) impurity in the high-Tc cuprates.Comment: 4 pages, 2 figures. submitted to Journal of the Physical Society of
Japa