Transport properties, upper critical field and anisotropy of Ba(Fe _0.75Ru_0.25)₂As₂ single crystals

The temperature and angle dependent resistivity of Ba(Fe _0.75Ru_0.25)₂As₂ single crystals were measured in magnetic fields up to 14 T. The temperature dependent resistivity with the magnetic field aligned parallel to c-axis and ab-planes allow us to derive the slope of dH _c2 ^ab /dT and dH _c2 ^c /dT near T _c yielding an anisotropy ratio Γ = dH _c2 ^ab /dT/dH _c2 ^c /dT≈2. By scaling the curves of resistivity vs. angle measured at a fixed temperature but different magnetic fields within the framework of the anisotropic Ginzburg-Landau theory, we obtained the anisotropy in an alternative way. Again we found that the anisotropy (m _c /m _ab )^1/2 was close to 2. This value is similar to that in Ba_0.6K _0.4Fe₂As₂ (K-doped Ba122) and Ba(Fe _0.92Co_0.08)₂As₂ (Co-doped Ba122). This suggests that the 3D warping effect of the Fermi surface in Ru-doped samples may not be stronger than that in the K-doped or Co-doped Ba122 samples, therefore the possible nodes appearing in Ru-doped samples cannot be ascribed to the 3D warping effect of the Fermi surface.