Enhancement of flux pinning by H+ and Xe+ irradiation in epitaxial thin films of Ba2YCu3O7−δ

Epitaxial Ba2YCu3O7−δ (BYCO) films grown by the ex situ BaF2 process are comparable to single crystals both in crystalline quality and the value and temperature dependence of the critical current (Jc) in an applied magnetic field in the BYCO (001) direction of Ha=0.9 T. With the appropriate dose of either 2 MeV H+ or 135Xe+, we can enhance Jc by a factor of 2 in Ha=0.9 T with little effect on Tc. This is significantly greater than the ∼25% enhancement previously reported for epitaxial BYCO films grown by in situ techniques [Roas, Hensel, and Saemann-Ischenko, Appl. Phys. Lett. 54, 1051 (1989)]. This provides the opportunity to isolate the induced defects and study their properties.