Liu Jixing, Zhang Shengnan, Li Meng, Sang Lina, Li Zhi, Cheng Zhenxiang, Zhao Weiyao, Feng Jianqing, Li Chengshan, Zhang Pingxiang, Dou Shixue, Wang Xiaolin, Zhou Lian
School of Materials Science and Engineering , Northeastern University , Shenyang 110819 , China.
Superconducting Materials Research Center , Northwest Institute for Nonferrous Metal Research , Xi'an 710016 , China.
ACS Appl Mater Interfaces. 2019 May 22;11(20):18825-18832. doi: 10.1021/acsami.9b02469. Epub 2019 Apr 30.
Fluorine-doped Fe(Se, Te) has been successfully synthesized using the melting method. A dual-oscillation effect was found in the F-doped sample, which combined both microstructural oscillation and chemical compositional oscillation. The microstructural oscillation could be attributed to alternate growth of tetragonal β-Fe(Se, Te) and hexagonal δ-Fe(Se, Te), which formed a pearlite-like structure and led to the enhancement of δ l flux pinning due to the alternating distributed nonsuperconducting δ-Fe(Se, Te) phase. The chemical compositional oscillations in β-Fe(Se, Te) phase were because of the inhomogeneously distributed Se and Te, which changes the pinning mechanism from surface pinning in the undoped sample to Δκ pinning in the 5% F-doped one. As a result, the critical current, upper critical field, and thermally activated flux-flow activation energy of FeSeTeF were enhanced by 7, 2, and 3 times, respectively. Our work revealed the physical insights into F-doping resulting in high-performance Fe(Se, Te) superconductors and inspired a new approach to optimize superconductivities in iron-based superconductors through phase and element manipulations.
采用熔融法成功合成了氟掺杂的Fe(Se, Te)。在氟掺杂样品中发现了双振荡效应，它结合了微观结构振荡和化学成分振荡。微观结构振荡可归因于四方β-Fe(Se, Te)和六方δ-Fe(Se, Te)的交替生长，它们形成了类似珠光体的结构，并且由于交替分布的非超导δ-Fe(Se, Te)相而导致δ l磁通钉扎增强。β-Fe(Se, Te)相中的化学成分振荡是由于Se和Te分布不均匀，这将钉扎机制从未掺杂样品中的表面钉扎转变为5%氟掺杂样品中的Δκ钉扎。结果，FeSeTeF的临界电流、上临界场和热激活磁通流激活能分别提高了7倍、2倍和3倍。我们的工作揭示了氟掺杂导致高性能Fe(Se, Te)超导体的物理见解，并启发了一种通过相和元素操纵来优化铁基超导体超导性的新方法。
