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 (ρ_ab≂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 YBa₂Cu₃O_7−δ with T_c(R=0) as high as 86 K have been grown on Sr₂RuO₄ crystals. The epitaxial growth of YBa₂Cu₃O_7−δ on Sr₂RuO₄ was revealed by four‐circle x‐ray diffraction as well as by transmission electron microscopy.