Possible Overestimation of I c Value of REBCO Tapes Due to the Narrow Bridge Fabricated by Laser Etching During Transport Measurements

Etching a narrow bridge on REBa2Cu3O7-x(REBCO, RE = Rare Earth) tape is a widely-applied procedure during transport measurements of critical current (Ic), aiming to mitigate significant Lorentz forces. However, the microbridge can influence the measurement accuracy, and understanding this influence is crucial because it can bias the extrapolation ofIcto the full tape width. In this paper, we reveal that the microbridge could result in an overestimation when extrapolating the full-widthIcvalues from microbridge ones. We identified two primary sources of this overestimation by systematically comparing the directly measured full-widthIcvalues with those extrapolated from narrow bridges under varying temperatures, applied magnetic fields, and field orientations. The first source arises from inaccuracies in the assumed cross-sectional geometry and area of the narrow bridge. Specifically, assuming a rectangular cross-section when the actual geometry is trapezoidal leads to significant overestimations. The second factor is the non-uniform pinning effect across the thickness of the REBCO layer. Although this effect is negligible at low magnetic fields and higher temperatures, it becomes significant at lower temperatures, high magnetic fields, and when the field is nearly parallel to the tape surface. Based on these findings, we propose an improved procedure for transport measurements using narrow bridges to achieve more accurate determinations ofIc.