# High-field transport properties of a P-doped BaFe2As2 film on technical substrate

## TL;DR

This study demonstrates that P-doped BaFe2As2 thin films on technical substrates exhibit high critical current densities in strong magnetic fields, making them promising for high-field magnet applications, with performance comparable to or exceeding existing superconductors.

## Contribution

First report of in-field transport properties of P-doped BaFe2As2 films on technical substrates, showing high Jc and flux pinning suitable for high-field applications.

## Key findings

- Jc exceeds 10^5 A/cm^2 at 15 T in both field directions
- Superior in-field Jc over MgB2 and NbTi, comparable to Nb3Sn above 20 T
- Flux flow along grain boundaries acts as flux pinning centers

## Abstract

High temperature (high-Tc) superconductors like cuprates have superior critical current properties in magnetic fields over other superconductors. However, superconducting wires for high-field-magnet applications are still dominated by low-Tc Nb3Sn due probably to cost and processing issues. The recent discovery of a second class of high-Tc materials, Fe-based superconductors, may provide another option for high-field-magnet wires. In particular, AEFe2As2 (AE: Alkali earth elements, AE-122) is one of the best candidates for high-field-magnet applications because of its high upper critical field, Hc2, moderate Hc2 anisotropy, and intermediate Tc. Here we report on in-field transport properties of P-doped BaFe2As2 (Ba-122) thin films grown on technical substrates (i.e., biaxially textured oxides templates on metal tapes) by pulsed laser deposition. The P-doped Ba-122 coated conductor sample exceeds a transport Jc of 10^5 A/cm^2 at 15 T for both major crystallographic directions of the applied magnetic field, which is favourable for practical applications. Our P-doped Ba-122 coated conductors show a superior in-field Jc over MgB2 and NbTi, and a comparable level to Nb3Sn above 20 T. By analysing the E-J curves for determining Jc, a non-Ohmic linear differential signature is observed at low field due to flux flow along the grain boundaries. However, grain boundaries work as flux pinning centres as demonstrated by the pinning force analysis.