Critical Current Characteristics of REBa₂Cu₃Oy Thin Films Deposited on a Zr-formed Substrate

Multifilamentation is effective in reducing AC losses in rare-earth-based high-temperature superconducting coated conductors (HTS-CCs). We have been working on separating superconducting films by patterning metal filaments on a substrate and then depositing a REBCO thin film by the Pulsed Laser Deposition (PLD) method. In our previous study, it was confirmed by electron beam backscatter diffraction (EBSD) that REBCO film deposited on Zr-filament showed dense formation of crystal grains with different orientations directions. However, the electrical properties have not yet been investigated. In this study, to investigate the electrical properties of REBCO thin films deposited on the Zr-filament, we have carried out magnetization distribution measurements by a scanning Hall-probe microscopy (SHPM) at 77 K, and current-voltage ( I-V ) measurement for the microbridges including the area of Zi-filament. A Zr-filament with about 100 µm in width and 4.5 mm in length was prepared on a 5 mm x 5 mm SrTiO 3 substrate and REBCO thin film was fabricated by PLD. From the SHPM measurement, magnetically separation has been confirmed. On the other hand, I-V measurements for microbridges of 200 µm in width and 500 µm in length have confirmed the superconducting transition, although the I c value was about 1/4 of that without Zr-filament at a low magnetic field. Comparing the magnetic field dependence of the critical current, the irreversible magnetic field was comparable, and the critical current is lower at a low magnetic field, suggesting that the current may flow through low-tilted grain boundaries. In addition, according to the SEM images, it is expected that the large lateral YBCO grains on Zr-filament determine the critical current.