Jc anisotropy for magnetic field angle in YBCO coated conductor on IBAD-MgO buffered metal tapes

We found that YBCO films deposited by the controlled process showed improved superconducting properties in magnetic fields, even without any artificial pinning centers such as BaZrO3 and BaSnO3. The YBCO films with a thickness of 450 nm were deposited on hastelloy tapes with a textured MgO buffer deposited by IBAD (Ion Beam Assist Deposition) method (IBAD-MgO) by PLD method. In the YBCO films on the IBAD-MgO (IBAD-YBCO), the critical current density of 2.9 MA/cm2 at 77 K in self-field and the ratio of Jc(B//c)/Jc(B//a, b) at 1 T was almost unity. Furthermore, we found that the Jc anisotropy changed with surface morphology on underlying buffer layer and YBCO thickness. This means that some c-axis correlated pinning centers are included in the films. From the cross-sectional TEM images of the IBAD-YBCO, there were not so many defects such as dislocations, Y2O3 inclusions and so on. Thus it is considered that some defects such as oxygen heterogeneity, displacement of a local composition and so on are pinning centers, although such defects can not be detected by a present analytical technique.