Exotic superconductivity and magnetism in ruthenates

Basic experimental and theoretical results on ruthenates and rutheno-cuprates are reviewed. The electronic structure of various ruthenates and exotic superconductivity in $\mathrm{Sr_2RuO_4}$ with spin-triplet pairing are described. The complex phase diagram of $\mathrm{Ca}_{2-x}\mathrm{Sr}_x\mathrm{RuO}_4$, involving competing magnetic phases and metal–insulator transitions, is described, as are the exotic magnetic properties of $\mathrm{Sr_3Ru_2O_7}$ and of the double perovskite $\mathrm{Sr_2YRuO_6}$, and the coexistence of superconductivity and magnetism in the rutheno-cuprate $\mathrm{RuSr_2GdCu_2O_8}$. Possible applications of $\mathrm{Sr_2RuO_4}$ and $\mathrm{SrRuO_3}$ are considered. The effect of strong electron correlations is discussed, and the properties of ruthenates and cuprates are compared.