Department of Crystalline Materials Science, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan.
Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, Mailbox R3-1, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan.
Sci Rep. 2017 Jan 12;7:39951. doi: 10.1038/srep39951.
High temperature (high-T) 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-T NbSn due probably to cost and processing issues. The recent discovery of a second class of high-T materials, Fe-based superconductors, may provide another option for high-field-magnet wires. In particular, AEFeAs (AE: Alkali earth elements, AE-122) is one of the best candidates for high-field-magnet applications because of its high upper critical field, H, moderate H anisotropy, and intermediate T. Here we report on in-field transport properties of P-doped BaFeAs (Ba-122) thin films grown on technical substrates by pulsed laser deposition. The P-doped Ba-122 coated conductor exceeds a transport J of 10 A/cm at 15 T for main crystallographic directions of the applied field, which is favourable for practical applications. Our P-doped Ba-122 coated conductors show a superior in-field J over MgB and NbTi, and a comparable level to NbSn above 20 T. By analysing the E - J curves for determining J, 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.
高温（高温）超导体如铜酸盐在磁场中的临界电流特性优于其他超导体。然而，用于高场磁体应用的超导线材仍然主要由低温 NbSn 主导，这可能是由于成本和加工问题。最近发现的第二类高温材料，铁基超导体，可能为高场磁体线材提供了另一种选择。特别是，AEFeAs（AE：碱土金属，AE-122）是高场磁体应用的最佳候选材料之一，因为它具有较高的上临界场 H、适中的 H 各向异性和中间 T。在这里，我们报告了通过脉冲激光沉积在技术衬底上生长的 P 掺杂 BaFeAs（Ba-122）薄膜的场内输运性质。P 掺杂 Ba-122 涂层导体在 15 T 的外加场主要晶向处的传输 J 超过 10 A/cm，这有利于实际应用。我们的 P 掺杂 Ba-122 涂层导体在磁场中的 J 优于 MgB 和 NbTi，在 20 T 以上与 NbSn 相当。通过分析用于确定 J 的 E-J 曲线，由于磁通沿晶界流动，在低场下观察到非欧姆线性微分特征。然而，正如钉扎力分析所示，晶界作为磁通钉扎中心发挥作用。
