High transport current superconductivity in powder-in-tube Ba_0.6K_0.4Fe₂As₂ tapes at 27 T

The high upper critical field and low anisotropy of iron-based superconductors (IBS) make them particularly attractive for high-field applications, especially for the construction of next-generation nuclear magnetic resonance spectrometers, particle accelerators and high-field magnets. However, for practical use it is essential to make IBS materials into wire and tape conductors with sufficient current carrying capability, which is limited by misaligned grains inside the conductors. Here, based on a simple and low-cost powder-in-tube (PIT) method, we demonstrate a high transport critical current density (J _c) reaching 1.5 × 10⁵ A cm^-2 (I _c = 437 A) at 4.2 K and 10 T in Ba_0.6K_0.4Fe₂As₂ (Ba-122) tapes by texturing the grain orientation with optimized hot-press technique. The transport J _c measured at 4.2 K under high magnetic fields of 27 T is still on the level of 5.5 × 10⁴ A cm^-2. Moreover, at 20 K and 5 T the transport J _c is also as high as 5.4 × 10⁴ A cm^-2, showing a promising application potential in moderate temperature range which can be reached by liquid hydrogen or cryogenic cooling. All these J _c values are the highest ever reported for IBS wires and tapes. The high-performance PIT Ba-122 tapes in this work suggest IBS to be a strong potential competitor of cuprate superconductors for the race of high-field applications in the future.