Superconducting Properties Of Nb Research Articles

Structural and superconducting properties of Nb3Sn film for superconducting radio-frequency cavities synthesized via bronze route

Superconducting Nb3Sn films were synthesized via the ex-situ annealing of Nb-coated bronze precursors. The precursors were prepared by sputtering 2 [Formula: see text]m of niobium film onto a bronze surface. The annealing was conducted in a vacuum tubular furnace at a temperature not higher than 700[Formula: see text]C. By changing the annealing time and temperature, a series of Nb3Sn samples with critical temperatures ([Formula: see text] > 16 K were obtained. X-ray diffraction confirmed the existence of the cubic Nb3Sn phase (A15 structure), whereas magnetic moment measurements indicated that critical temperature of the studied samples ranged from 16.2 to 16.5 K. Therefore, this study explores a new technique appropriate for creating copper-based Nb3Sn thin-film-coated superconducting radio-frequency (TFSRF) cavities.

Magnetic and superconducting phase diagram of Nb/Gd/Nb trilayers

We report on a study of the structural, magnetic and superconducting properties of Nb(25nm)/Gd($d_f$)/Nb(25nm) hybrid structures of a superconductor/ ferromagnet (S/F) type. The structural characterization of the samples, including careful determination of the layer thickness, was performed using neutron and X-ray scattering with the aid of depth sensitive mass-spectrometry. The magnetization of the samples was determined by SQUID magnetometry and polarized neutron reflectometry and the presence of magnetic ordering for all samples down to the thinnest Gd(0.8nm) layer was shown. The analysis of the neutron spin asymmetry allowed us to prove the absence of magnetically dead layers in junctions with Gd interlayer thickness larger than one monolayer. The measured dependence of the superconducting transition temperature $T_c(d_f)$ has a damped oscillatory behavior with well defined positions of the minimum at $d_f$=3nm and the following maximum at $d_f$=4nm; the behavior, which is in qualitative agreement with the prior work (J.S. Jiang et al, PRB 54, 6119). The analysis of the $T_c(d_f)$ dependence based on Usadel equations showed that the observed minimum at $d_f$=3nm can be described by the so called "$0$" to "$\pi$" phase transition of highly transparent S/F interfaces with the superconducting correlation length $\xi_f \approx 4$nm in Gd. This penetration length is several times higher than for strong ferromagnets like Fe, Co or Ni, simplifying thus preparation of S/F structures with $d_f \sim \xi_f$ which are of topical interest in superconducting spintronics.

Fabrication and characterization of hot-electron bolometers for THz applications

Superconducting properties of Nb and NbN thin films for application in diffusion and phonon cooled Hot-Electron Bolometers have been systematically investigated. The materials were sputtered on fused quartz substrates in a wide thickness range. DC-measurements of the Nb films allow us to predict the intermediate frequency bandwidth of a hot-electron bolometer mixer device for a given design. To improve the characteristics of the NbN thin films, we used a 15 nm MgO seed layer.

A NOTE ON SOME OF THE INTERMEDIATE PHASES IN THE Nb–Sn SYSTEM

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