Abstract Body

Narrowing REBa₂Cu₃O_y (REBCO) tapes is effective in reducing AC losses, and mechanical cutting with a slit blade or laser cutting is commonly used.However, these narrowing methods may cause damage to the superconducting layer near the cutting edge. Therefore, we have focused on a separation method by patterning metal stripes on the substrate prior to the REBCO deposition process.In this study, to confirm the effect of Zr on the separation of superconducting films, we formed a wide-width Zr stripe and investigated the superconducting properties near the Zr. Specifically, we formed a Zr stripe with 106 µm in width and 550 nm in height, on a 5 mm square SrTiO₃ substrate by photolithography and sputtering.Then, YBCO films were deposited on the Zr-formed substrate using the pulsed laser deposition method.

First, we observed the trapped magnetic field distribution by Scanning Hall-Probe Microscopy to confirm the separation of the magnetization in the films. The result showed that the magnetic field strength was significantly reduced in the region where Zr was expected to be located.

After that, we fabricated microbridges and measured I-V characteristics using a Physical Property Measurement System. The microbridges of 200 µm in width and 500 µm in length were fabricated perpendicular to the Zr stripe. As a comparison, microbridges without Zr stripe were also fabricated in the same size. The results showed that the I-V characteristics of the microbridge passing over the Zr stripe showed the superconducting transition below T_c,although the I_c was lower than that of the microbridge without Zr stripe. This suggests that a superconducting matrix is formed on the Zr.In addition, temperature and magnetic field dependence of I_c showed that the differences in I_c values of the bridges with and without Zr stripe were more than four times at low magnetic fields, and the differences became smaller at high magnetic fields, indicating that the irreversible magnetic fields were almost the same.This result seems to be consistent with the report [1] that the critical current at low magnetic field decreases as the tilt angle of grain boundaries increases.Therefore, it is possible that REBCO deposited on Zr stripe may be crystalline oriented and connected by low-tilt grain boundaries. The details of the results will be discussed.

References

[1] H. Hilgenkamp et al.; “Grain boundaries in high-T_c superconductors” Rev. Mod. Phys., Vol. 74, No. 2, April 2002

Acknowledgment

This work was supported in part by the Joint Research Hub Program of NIMS and by JSPS Grants-in-Aid for Scientific Research JP22H2019 and JP22H02021.

Keywords: REBa₂Cu₃O_y, Photolithography, Zirconium-stripe, Microbridge