Large differences of critical current density in thin films of superconducting YBa2Cu3O7−x

Abstract

Thin films of YBa2 Cu3 O7−x with three types of c-axis alignment have been prepared by evaporation: unaligned films on oxidized silicon with zero-resistance transition temperatures as high as 88 K (the highest value reported for thin films of this superconductor on this substrate), films with regions aligned along each of the three 〈100〉 directions of the (100) SrTiO3 substrate, and films with the c-axis perpendicular to the (100) SrTiO3 plane. Typical values of critical current density (A cm −2 ) at 77 K are 102 , 3×104 , and 106, respectively. The temperature dependence of the critical current density is similar for the three types of films; it increases linearly with decreasing temperature, which is suggestive of a flux creep-limited model.