The effect of MgB2 layer thickness on superconducting properties of MgB2/Ni multilayer thin films

摘要

We have investigated the influence of MgB2 layer thickness on the superconducting properties of MgB2/Ni multilayer thin films. Multilayer thin films were prepared using an alternate growth of MgB2 (31, 22, and 15 nm in thickness) and Ni (similar to 1 nm) layers. The critical temperature, T-c, upper critical field, B-c2, and magnetic irreversibility field, B-irr, values decreased as the MgB2 layer become thinner. In the multilayer thin films, the critical current density, J(c), was higher in fields parallel to the substrate than in perpendicular fields, reflecting the layered nanostructure parallel to the substrate. On decreasing the MgB2 layer thickness, the peak position of the global pinning force, F-p, curves moved to higher magnetic field. These peak shifts could be explained by a matching effect of the flux lines with the periodic multilayer nanostructure.