Influence of Discontinuous Columnar Defects on Flux Pinning Properties in GdBCO Coated Conductors

To investigate the effect of discontinuity of 1-D pinning centers on the flux pinning in a wide range of magnetic field directions, discontinuous columnar defects (CDs) and continuous CDs were formed in GdBCO coated conductors using Xe-ion irradiations with 80 and 270 MeV, respectively. An overall shift upward in J_c, for the 80-MeV-irradiated sample compared to the 270-MeV-irradiated one, can be observed in every direction of magnetic field, which is more remarkable as temperature decreases. This implies a synergetic effect of the pinning interaction between the linearity and the discontinuity for the discontinuous CDs. When the density of CDs is lower, however, the difference in Jc between the discontinuous and the continuous CDs becomes less at lower temperature, even in the magnetic field parallel to the c-axis. At lower density of CDs, the average spacing between CDs is wider, which would hardly lead to automatic entanglement of flux lines in the discontinuous CDs, i.e., to the synergetic effect.