Effects of In-Plane Impurity Substitution in Sr₂RuO₄

Abstract

We report comparative substitution effects of nonmagnetic Ti⁴⁺ and magnetic Ir⁴⁺ impurities for Ru⁴⁺ 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. The behavior observed in Sr₂RuO₄ is similar to that of the nonmagnetic (Zn²⁺) impurity in the high-T_c cuprates, but different from that of the magnetic (Ni²⁺) impurity.