Superconducting transitions of Y-123/Ba-Ca-Cu-O/Y-123 layered structure

Abstract

The highest critical temperature reported for the superconducting system Ba-Ca-Cu-O is Tc=117K. We have investigated the fabrication of systems consisting of Ba-Ca-Cu-O mid-layers sandwiched by YBa2Cu3O7-δ(Y-123) films. These trilayered structures were fabricated using pulsed laser deposition under 13.3Pa O2 pressure and on a SrTiO3 (100) substrate heated to 800–850°. The base Y-123 films were fabricated with the c-axis orientation and the roughness of all films was investigated using reflection high energy electron diffraction. We have not yet achieved a value of Tc above 100K. However, three successive onset superconducting transitions were observed in the magnetic susceptibility, for example at Tc-on = 76.8K, 81.0K and 85.7K for systems with a BaCa2Cu3Ox mid-layer. These three transitions, Tc1, Tc2 and Tc3, were assigned to the base and top Y-123 layers (thickness 100nm) and the BaCanCun+10z mid-layer (thickness 45nm), respectively. Moreover, the superconductive transition determined by resistivity measurements of Y-123/Ba2CanCun+10z/Y-123 trilayers was sharper (Tc=91.7–89.4) than that of Y-123 alone (Tc=92.2–88.2).