Haberkorn, N., S. Suárez, P. D. Pérez, H. Troiani, P. Granell, F. Golmar, J. - H. Lee, and S. H. Moon. "Effect of mixed pinning landscapes produced by 6 MeV oxygen irradiation on the resulting critical current densities Jc in 1.3 µm thick GdBa2Cu3O7-d coated conductors grown by co-evaporation." Physica C: Superconductivity and its Applications 542 (2017): 6–11.
Abstract: We report the influence of crystalline defects introduced by 6 MeV 16O3+ irradiation on the critical current densities Jc and flux creep rates in 1.3 µm thick GdBa2Cu3O7-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 × 1013 cm−2 and 4 × 1014 cm−2. The irradiations were performed with the ion beam perpendicular to the surface of the samples. The Jc 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 Jc dependences can be significantly improved by irradiation. For doses of 1 × 1014 cm−2 the Jc values at μ0H = 5 T are doubled without affecting significantly the Jc 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 × 1014 cm−2, these values drop to μ = 1.45 and μ = 1.24, respectively
|
|
Haberkorn, N., Y. Coulter, A. M. Condó, P. Granell, F. Golmar, H. S. Ha, and S. H. Moon. "Vortex creep and critical current densities Jc in a 2μm thick SmBa2Cu3O7−d coated conductor with mixed pinning centers grown by co-evaporation." Superconductor Science and Technology 29 (2016): 075011.
|
Haberkorn, N., Kim Jeehoon, S. Suárez, Jae- Hun Lee, and S. H. Moon. "Influence of random point defects introduced by proton irradiation on the flux creep rates and magnetic field dependence of the critical current density J c of co-evaporated GdBa 2 Cu 3 O 7− δ coated conductors." Superconductor Science and Technology 28, no. 12 (2015): 125007.
Abstract: We report the influence of random point defects introduced by 3 MeV proton irradiation (doses of 0.5 × 10 16 , 1 × 10 16 , 2 × 10 16 and 6 × 10 16 cm −2 ) on the vortex dynamics of co-evaporated 1.3 μ m thick, GdBa 2 Cu 3 O 7− δ coated conductors. Our results indicate that the inclusion of additional random point defects reduces the low field and enhances the in-field critical current densities J c . The main in-field J c enhancement takes place below 40 K, which is in agreement with the expectations for pinning by random point defects. In addition, our data show a slight though clear increase in flux creep rates as a function of irradiation fluence. Maley analysis indicates that this increment can be associated with a reduction in the exponent μ characterizing the glassy behavior.
|
Haberkorn, N., J. Guimpel, S. Suárez, H. E. Troiani, P. Granell, F. Golmar, J. - H. Lee, S. H. Moon, and H. Lee. "Strong influence of the oxygen stoichiometry on the vortex bundle size and critical current densities J c of GdBa 2 Cu 3 O x -coated conductors grown by co-evaporation." Superconductor Science and Technology 30, no. 9 (2017): 095009.
Abstract: We report on the influence of oxygen stoichiometry on the vortex creep mechanism of GdBa 2 Cu 3 O x -coated conductors produced by co-evaporation. The oxygen stoichiometry of the films, x , was modified in a controlled way between 6.85 and 7, which resulted in systematic and reversible control of the superconducting critical temperature between about 78 and 93 K. The change in the oxygen stoichiometry produces a strong reduction in the self-field critical current densities J c without significantly modifying the power-law dependence at intermediate magnetic fields, which indicates a negligible contribution of oxygen vacancies to the pinning. In addition, the characteristic glassy exponent μ shows a systematic diminution from about 1.63 at x = 7 to about 1.12 at x = 6.85. The results are compared with those obtained for proton- and oxygen-irradiated films, in which the vortex dynamics is determined by a balance between the improved pinning, originating from nanocluster inclusion, and the suppressed superconducting properties due to disorder in the nanoscale.
|
