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Enhancement of the superconducting transition temperature of FeSe by intercalation of a molecular spacer layer

Nature Materials volume 12, pages 15–19 (2013)Cite this article

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Abstract

The discovery of high-temperature superconductivity in a layered iron arsenide1 has led to an intensive search to optimize the superconducting properties of iron-based superconductors by changing the chemical composition of the spacer layer between adjacent anionic iron arsenide layers2,3,4,5,6,7. Superconductivity has been found in iron arsenides with cationic spacer layers consisting of metal ions (for example, Li+, Na+, K+, Ba2+) or PbO- or perovskite-type oxide layers, and also in Fe1.01Se (ref. 8) with neutral layers similar in structure to those found in the iron arsenides and no spacer layer. Here we demonstrate the synthesis of Lix(NH2)y(NH3)1−yFe2Se2 (x~0.6; y~0.2), with lithium ions, lithium amide and ammonia acting as the spacer layer between FeSe layers, which exhibits superconductivity at 43(1) K, higher than in any FeSe-derived compound reported so far. We have determined the crystal structure using neutron powder diffraction and used magnetometry and muon-spin rotation data to determine the superconducting properties. This new synthetic route opens up the possibility of further exploitation of related molecular intercalations in this and other systems to greatly optimize the superconducting properties in this family.

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Figure 1: The 298 K crystal structure of Li0.6(1)(ND2)0.2(1)(ND3)0.8(1)Fe2Se2.
Figure 2: Rietveld refinement against GEM data for Li0.6(1)(ND2)0.2(1)(ND3)0.8(1)Fe2Se2 at 298 K.
Figure 3: Magnetic susceptibility measurements.
Figure 4: Analysis of μSR spectroscopy measurements.

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Acknowledgements

We are grateful to the ISIS facility including the GEM Xpress service for access to neutron and muon instruments and we thank A. Daoud-Aladine and R. I. Smith for technical assistance at ISIS. We acknowledge financial support from the UK EPSRC (grant EP/I017844/1) and STFC (grant EP/G067481/1).

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Authors and Affiliations

  1. Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK

    Matthew Burrard-Lucas, David G. Free, Stefan J. Sedlmaier, Simon J. Cassidy, Yoshiaki Hara, Alex J. Corkett & Simon J. Clarke

  2. Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK

    Jack D. Wright & Stephen J. Blundell

  3. Department of Natural Science, Ibaraki National College of Technology, Nakane 866, Hitachinaka 312-8508, Japan

    Yoshiaki Hara

  4. Department of Physics, Durham University, South Road, Durham DH1 3LE, UK

    Tom Lancaster

  5. ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, UK

    Peter J. Baker

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  1. Matthew Burrard-Lucas
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Contributions

M.B-L., D.G.F., Y.H. and S.J.S. prepared the samples, D.G.F., A.J.C., S.J.S. and S.J. Clarke performed the diffraction data collection and structural analysis. J.D.W., T.L., P.J.B. and S.J.B. performed the μSR measurements, M.B-L., S.J. Cassidy, A.J.C. and S.J. Clarke performed the magnetometry and other characterization measurements. S.J. Clarke conceived the project and, with S.J.B., wrote the manuscript.

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Correspondence to Simon J. Clarke.

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Burrard-Lucas, M., Free, D., Sedlmaier, S. et al. Enhancement of the superconducting transition temperature of FeSe by intercalation of a molecular spacer layer. Nature Mater 12, 15–19 (2013). https://doi.org/10.1038/nmat3464

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