Sr₂RuO₄: A metallic substrate for the epitaxial growth of YBa₂Cu₃O_7-δ

Single crystals of Sr2RuO4 were grown by the floating zone melting technique. The crystals have the K2NiF4 structure and display a metallic resistivity behavior in the a-b-plane between 300 and 4.2 K (ρab≅10-4 Ω cm at 300 K). The in-plane lattice mismatch between YBa2Cu3O 7-δ (001) and Sr2RuO4 (001) is smaller than 1.3%, better than that to SrTiO3 {100}. Epitaxial films of YBa2Cu3O7-δ with Tc(R=0) as high as 86 K have been grown on Sr2RuO4 crystals. The epitaxial growth of YBa2Cu3O7-δ on Sr2RuO4 was revealed by four-circle x-ray diffraction as well as by transmission electron microscopy.