Magnetic ordering in Sr₂RuO₄ induced by nonmagnetic impurities

We report unusual effects of nonmagnetic impurities on the spin-triplet superconductor Sr₂RuO₄. The substitution of nonmagnetic Ti⁴⁺ for Ru⁴⁺ induces localized-moment magnetism characterized by unexpected Ising anisotropy with the easy axis along the interlayer c direction. Furthermore, for x(Ti)>~0.03 magnetic ordering occurs in the metallic state with the remnant magnetization along the c axis. We argue that the localized moments are induced in the Ru⁴⁺ and/or oxygen ions surrounding Ti⁴⁺ and that the ordering is due to their interaction mediated by itinerant Ru-4d electrons with strong spin fluctuations.