Structure and superconducting properties of Nb-Ti nanocomposites produced by rolling method

摘要

We have studies multilayered composites wherein alloys Nb-31 wt.%Ti and Nb-50 wt.%Ti alternate with Nb layers. The lay ers thickness varied from ~ 140 to ~ 10 nm. The composites were produced by 3-cycle rolling of multilayered packets.Each cycle in volved vacuum rolling with heating to 950℃ ,followed by rolling at room temperature. As evidenced by the large anisotropy of the critical current density,Nb layers cause a strong pinning of superconducting vortices at the superconductor-normal interface. The second critical magnetic field H_c2,calculated from the experiments on measuring H_c2 near the critical temperature,was less intense than that of the ordi nary single-layered ribbon and it decreased as the number of layers grew.