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SCIENCE CHINA Materials, Volume 62, Issue 9: 1357-1362(2019) https://doi.org/10.1007/s40843-019-9438-7

BaTh2Fe4As4(N0.7O0.3)2: An iron-based superconductor stabilized by inter-block-layer charge transfer

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  • ReceivedMay 8, 2019
  • AcceptedMay 8, 2019
  • PublishedMay 10, 2019

Abstract

本文基于结构设计、采用高温固相反应, 首次合成了电子掺杂“12442”型超导体BaTh2Fe4As4(N0.7O0.3)2. 研究发现, “BaFe2As2”和“ThFeAsN0.7O0.3”块层间的电荷转移是稳定该目标化合物的必要条件. 霍尔测量证实该化合物主要为电子型导电. 电阻、直流磁化率和比热测量的综合结果表明, 样品在22 K呈现体超导电性.


Funded by

the National Key Research and Development Program of China(2017YFA0303002)

the Fundamental Research Funds for the Central Universities of China(2019FZA3004)


Acknowledgment

This work was supported by the National Key Research and Development Program of China (2017YFA0303002) and the Fundamental Research Funds for the Central Universities of China (2019FZA3004).


Interest statement

The authors declare no competing financial interest.


Contributions statement

Cao GH designed the experiment, discussed the results and wrote the paper. Wang ZC and Wang C also contributed the research idea and discussed the results. Shao YT synthesized the samples, performed the structural characterizations and physical property measurements with assistance from Li BZ, Wu SQ, Wu JF, Ren Z, Qiu SW, and Rao C.


Author information

Ye-Ting Shao is currently a graduate student at the Department of Physics, Zhejiang University. His research focuses on the explorations and physical property measurements of novel superconductors.


Guang-Han Cao is a professor at the Department of Physics, Zhejiang University. He received his PhD degree from the University of Science and Technology of China in 1995, and then became a postdoctoral fellow in Zhejiang University where he has stayed until present. He visited the National Institute for Materials Sciences, Japan, from 1999 to 2001, and he also worked as a visiting professor at the Institute of Solid State Physics of the University of Tokyo in 2011. His research interests include the exploratory synthesis, structural characterizations and physical-property measurements of novel superconductors and other related materials.


Supplement

Supplementary information

Experimental details and supporting data are available in the online version of the paper.


References

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  • Figure 1

    XRD patterns of the BaTh2Fe4As4(N1−xOx)2 samples with x = 0 (bottom) and 0.3 (top). Shown on the right is the expected crystal structure that is stabilized by the charge transfer from the 1111-type block to the 122-type one.

  • Figure 2

    Rietveld refinement of the powder XRD of BaTh2Fe4As4(N0.7O0.3)2 from which the crystal structure was determined (shown in the right-hand inset). The middle inset shows the structural parameters of the Fe2As2 layer.

  • Figure 3

    Temperature dependence of resistivity for the BaTh2Fe4As4-(N0.7O0.3)2 polycrystalline sample. The solid pink line represents the data fitting with the formula shown (n = 1.87). The upper-left inset shows the superconducting transitions under external magnetic fields, and the lower-right inset plots the upper critical field (Hc2) defined in the text.

  • Figure 4

    Temperature dependence of magnetic susceptibility (a) and specific heat (b) for BaTh2Fe4As4(N0.7O0.3)2. The top inset shows a close-up for the onset superconducting transition. The bottom inset plots the specific-heat difference, from which a bulk superconducting transition at ~22 K is revealed.

  • Figure 5

    Field dependence of Hall resistance of the BaTh2Fe4As4-(N0.7O0.3)2 sample. The inset plots the Hall coefficient (RH) as a function of temperature.

  • Table 1   Crystallographic data for BaThFeAs(NO) (space group: 4/, No. 139) at room temperature. The lattice parameters are = and =

    Atom

    Site

    x

    y

    z

    Occ.a

    Bisob

    Ba

    2a

    0

    0

    0

    1.0

    1.7(7)

    Th

    4e

    0.5

    0.5

    0.20839(4)

    1.0

    0.12(3)

    Fe

    8g

    0.5

    0

    0.10757(13)

    1.0

    0.70(9)

    As1

    4e

    0.5

    0.5

    0.06399(11)

    1.0

    0.19(9)

    As2

    4e

    0

    0

    0.15261(10)

    1.0

    0.2

    N/O

    4d

    0.5

    0

    0.25

    1.0

    1.5

    The occupancy of each atom was fixed to be 1.0 in the Rietveld refinement. b) The B factors of As2 and N/O were fixed to avoid an unphysical negative value.

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