Measurements of the superconducting fluctuations in optimally doped BaFe2−xNixAs2 under high magnetic fields: probing the 3D-anisotropic Ginzburg–Landau approach

The superconducting fluctuations well inside the normal state of Fe-based superconductors were experimentally studied through the in-plane paraconductivity in several high-quality, optimally doped BaFe2-xNixAs2 crystals. These measurements were performed in magnetic fields with amplitudes up to 14 T, and different orientations relative to the c-axis of the crystals (theta = 0 degrees, 53 degrees, and 90 degrees). The results allowed a stringent check of the applicability of a recently proposed Ginzburg-Landau approach for the fluctuating electrical conductivity of three-dimensional (3D) anisotropic materials in the presence of finite applied magnetic fields.