Irradiation-induced enhancement of the critical current density of epitaxial YBa2Cu3O7−x thin films

Abstract

Thin films of YBa₂Cu₃O_7−x have been prepared epitaxially on 〈100〉 SrTiO₃ by laser evaporation in a single‐step process. The resistivity of the films decreases linearly with temperature and is measured to 80 μΩ cm at 100 K. The samples are completely superconducting at 88 K. The critical current densities are as high as 5×10⁶ A/cm² at 77 K in strip lines of 8 μm width. Irradiation with 25 MeV ¹⁶O ions at 77 K combined with in situ measurements was applied to study the influence of lattice disorder on superconducting properties. The resistivity ρ increases, whereas the critical superconducting temperature T_c0 and the critical current density j_c in the absence of a magnetic field decrease proportionally to the ion fluence. Contrary to this behavior, we observe an enhancement of j_c in magnetic fields larger than 1 T. The maximum enhancement is about a factor of 2 at a fluence of 10^{14 16}O/cm². This increase is due to pinning at...