Effect of mixed pinning landscapes produced by 6 MeV oxygen irradiation on the resulting critical current densities J c in 1.3 µm thick GdBa 2 Cu 3 O 7- d coated conductors grown by co-evaporation

Abstract

We report the influence of crystalline defects introduced by 6 MeV 16 O 3+ irradiation on the critical current densities J c and flux creep rates in 1.3 µm thick GdBa 2 Cu 3 O 7- δ coated conductor produced by co-evaporation. Pristine films with pinning produced mainly by random nanoparticles with diameter close to 50 nm were irradiated with doses between 2 × 10 13 cm −2 and 4 × 10 14 cm −2 . The irradiations were performed with the ion beam perpendicular to the surface of the samples. The J c and the flux creep rates were analyzed for two magnetic field configurations: magnetic field applied parallel (H║c) and at 45° (H║45°) to the c-axis. The results show that at temperatures below 40 K the in-field J c dependences can be significantly improved by irradiation. For doses of 1 × 10 14 cm −2 the J c values at μ 0 H = 5 T are doubled without affecting significantly the J c at small fields. Analyzing the flux creep rates as function of the temperature in both magnetic field configurations, it can be observed that the irradiation suppresses the peak associated with double-kink relaxation and increases the flux creep rates at intermediate and high temperatures. Under 0.5 T, the flux relaxation for H‖c and H||45° in pristine films presents characteristic glassy exponents μ = 1.63 and μ = 1.45, respectively. For samples irradiated with 1 × 10 14 cm −2 , these values drop to μ = 1.45 and μ = 1.24, respectively