FABRICATION OF GRAIN BOUNDARY JUNCTIONS USING NdFeAs(O,F) SUPERCONDUCTING THIN FILMS

We report on the growth of NdFeAs(O,F) thin films on [001]-tilt MgO bicrystal substrates with misorientation angle θ _GB=6°, 12°, 24° and 45°, and their inter- and intra-grain transport properties. X-ray diffraction study confirmed that all our NdFeAs(O,F) films are epitaxially grown on the MgO bicrystals. The θ _GB dependence of the inter-grain critical current density J _c shows that, unlike Co-doped BaFe₂As₂ and Fe(Se,Te), its decay with θ _GB is rather significant. As a possible reason of this result, fluorine may have diffused preferentially to the grain boundary region and eroded the crystal structure. (paper)