The Visualization of Current-Limiting Defects in Yba2cu3o7 Films on Ion-Beam Assisted Deposition Buffer Layers of Yttrium-Stabilized Zro2 and Gd2zr2o7

For the production of high-current-carrying, long-length superconducting wires or tapes, it is necessary to use biaxially textured metallic substrates or buffer layers. Though being highly textured, the deposited superconducting film exhibits a complex defect structure which (locally) suppresses the critical current and alternates characteristically the magnetic flux distribution seen in magneto-optical imaging. In this paper, we report on pulsed laser deposited YBaCuO films on biaxially textured yttrium-stabilized ZrO2 (YSZ) and Gd2Zr2O7 (GZO) buffers which were grown by ion beam assisted deposition (IBAD) on polycrystalline substrates. The current-limiting defect structure turns out to resemble closely a combination of a dense distribution of pinhole-like induced growth distortions and a fine grain boundary network. The current suppression is caused on the one hand by the dense packing of pinhole-like defects. On the other hand, we observe a substantial current anisotropy being related to the surface morphology of the buffer layers and the direction of the IBAD-beam.