Decoupling Resistive Onset from the Irreversibility Field in High-Temperature Superconducting Coated Conductors

The irreversibility field (Hirr) marks the boundary below which flux lines are effectively pinned, enabling large, dissipation-free currents in type-II superconductors. In early high-temperature superconductors (HTS), the onset of electrical resistance in transport measurements was empirically observed to coincide with Hirr, leading to the widespread practice of using resistive transition as a proxy for the irreversibility line. This equivalence has since become a standard evaluation protocol, even for modern engineered materials. However, we demonstrate that this assumption no longer holds for REBCO-based coated conductors. Using combined magnetization and transport data from commercial tapes, we show a significant decoupling between μ0Hirr ≈ 2.7 T and the resistive onset at ~6.4 T at 77 K—near the magnetically measured upper critical field Hc2. Relying solely on low-current transport measurements risks overestimating performance and compromising device reliability. Our findings call for a paradigm shift in the characterization of advanced HTS materials, emphasizing the necessity of complementary magnetic and electrical techniques to accurately assess their applicability limits.