Superconducting and Critical Current Properties of NiBi$_{3}$ Microfibers and Thin Films

We report the superconducting and critical current properties of thin films of NiBi$_{3}$ formed on the surface of carbon microfibers and on sapphire substrates. The NiBi$_{3}$ coated C-fibers were prepared by reacting 7-\textit{$\mu $}m diameter Ni-coated carbon fibers with Bi shot, and the thin films on sapphire were formed by exposing electron-beam deposited Ni films to Bi vapor. The fibers and films show T$_{c}$ = 4.25 K and T$_{c}$ = 4.35 K, respectively, which was slightly higher than that of bulk polycrystalline NiBi$_{3}$. The extrapolated upper critical fields of the fibers [H$_{c2}$(0) = 12 T] and films [H$_{c2}$(0) = 9 T] are higher than the reported data on polycrystalline samples. The temperature dependence of the critical current density ($J_{c})$ is well described by Ginzburg-Landau theory and gives an extrapolated value of 5.26 $\times $ 10$^{5}$ A/cm$^{2}$.