Superconducting and magnetotransport properties of ZnNNi3 microfibers and films

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We present the superconducting and critical current properties of ZnNNi3 in the form of annularly coated carbon microfibers and thin films. The fibers were prepared by heating 6-8μm diameter commercially available Ni-coated carbon fibers with Zn powder in a flowing stream of NH3 gas at 650°C. The fibers had a Tc =3.75K, which was slightly higher than that of the polycrystalline powder and an upper critical field, Hc2 (0) =0.92T. Near the transition temperature Tc, the critical current density Jc was well described by the Ginzburg-Landau power-law form [1- (T/ Tc) 2] 3/2. The extrapolation produces Jc (0) ≅1.45× 106 A/ cm2. An axial magnetic field produces an exponential decrease in the critical current density. Planar ZnNNi3 films were formed on sapphire substrates by exposing thin Ni films to a similar heat treatment as the fibers. Hall measurements on the films in the normal state revealed a carrier density, n=-1.46× 1023 cm-3. © 2009 The American Physical Society.

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Physical Review B - Condensed Matter and Materials Physics

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