Upper critical field and superconducting anisotropy of BaFe_2-xRu_xAs₂(x=0.48 and 0.75) single crystals

Abstract

The upper critical field (H c2 ) was determined by applying a magnetic field along the ab plane and c axis for two single crystals of BaFe 2-x Ru x As 2 (x=0.48 and 0.75). The anisotropy of the H c2 (0), γ(0)=H c2 ab (0)/H c2 c (0), was ~1.6 for x=0.48 and ~2.3 for x=0.75. The angle-dependent resistance measured below T c allowed perfect scaling features based on anisotropic Ginzburg-Landau theory, leading to consistent anisotropy values. Because only one fitting parameter γ is used in the scaling for each temperature, the validity of the γ value was compared with that determined from γ=H c2 ab /H c2 c . The γ obtained at a temperature close to T c was 3.0 and decreased to 2.0 at low temperatures. Comparing to the anisotropy determined for electron-or hole-doped BaFe 2 As 2 using the same method, the present results point to consistent anisotropy in Ru-doped BaFe 2 As 2 with other electron-or hole-doped BaFe 2 As 2 .