Flux pinning properties of ErBa2Cu3Oy thin films with BaZrO3 nanorods

ErBa2Cu3Oy (ErBCO) thin films with BaZrO3 (BZO) nanorods were prepared by a PLD method for an enhancement of the critical current density J(c). The values of J(c) for the ErBCO thin film containing 1.5 wt% BZO (Er15) in magnetic fields are higher than those for the ErBCO thin film containing 0.5 wt% BZO (Er05). The peaks of J(c) have been observed in the angular dependence of Jc in both the films when the magnetic field is applied parallel to the c-axis. It has been found that the peak is attributed to the flux pinning by BZO nanorods oriented parallel to the c-axis. The vortex glass - liquid transition temperature T-g and the pinning parameter m were derived by fitting observed electric transport properties to the theoretical expression based on the percolation transition model. The value of Tg of Er15 is higher than that of Er05. This result indicates that the vortex glass phase extends to a higher temperature region on increasing the fraction of BZO. The peak of m has been found in the magnetic field dependence. This fact is probably due to matching the density of BZO nanorods with that of fluxoids, which was confirmed by TEM observations.