Letter | Published:

Coexistence of static magnetism and superconductivity in SmFeAsO1−xFx as revealed by muon spin rotation

Nature Materials volume 8, pages 310314 (2009) | Download Citation


The recent observation of superconductivity with critical temperatures (Tc) up to 55 K in the pnictide RFeAsO1−xFx, where R is a lanthanide, marks the first discovery of a non-copper-oxide-based layered high-Tc superconductor1,2,3. It has raised the suspicion that these new materials share a similar pairing mechanism to the cuprate superconductors, as both families exhibit superconductivity following charge doping of a magnetic parent material. In this context, it is important to follow the evolution of the microscopic magnetic properties of the pnictides with doping and hence to determine whether magnetic correlations coexist with superconductivity. Here, we present a muon spin rotation study on SmFeAsO1−xFx, with x=0–0.30 that shows that, as in the cuprates, static magnetism persists well into the superconducting regime. This analogy is quite surprising as the parent compounds of the two families have rather different magnetic ground states: itinerant spin density wave for the pnictides contrasted with the Mott–Hubbard insulator in the cuprates. Our findings therefore suggest that the proximity to magnetic order and associated soft magnetic fluctuations, rather than strong electronic correlations in the vicinity of a Mott–Hubbard transition, may be the key ingredients of high-Tc superconductors.

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This work is supported by the Schweizer Nationalfonds (SNF) by grant 200020-119784 and the NCCR program MANEP, the Deutsche Forschungsgemeinschaft (DFG) by grant BE2684/1-3 in FOR538 and the UK EPSRC. We acknowledge helpful discussions with D. Baeriswyl, A. T. Boothroyd and M. Siegrist.

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  1. University of Fribourg, Department of Physics and Fribourg Centre for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland

    • A. J. Drew
    • , V. K. Malik
    • , A. Dubroka
    • , M. Rössle
    • , K. W. Kim
    •  & C. Bernhard
  2. Queen Mary University of London, Department of Physics, Mile End Road, London E1 4NS, UK

    • A. J. Drew
  3. Laboratory for Neutron Scattering, Paul Scherrer Institut & ETH Zürich, CH-5232 Villigen, Switzerland

    • Ch. Niedermayer
  4. Oxford University, Department of Physics, Clarendon Laboratory, Oxford OX1 3PU, UK

    • P. J. Baker
    • , S. J. Blundell
    •  & T. Lancaster
  5. ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, UK

    • F. L. Pratt
  6. Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China

    • R. H. Liu
    • , G. Wu
    •  & X. H. Chen
  7. RIKEN-RAL, Nishina Centre, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan

    • I. Watanabe
  8. Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen, Switzerland

    • C. Baines


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A.J.D, Ch.N., F.L.P., S.J.B., T.L., I.W., C. Baines and C. Bernhard carried out the muon experiments. A.J.D, Ch.N., F.L.P., S.J.B. and C.B(2) analysed and interpreted the results. A.J.D., P.J.B., S.J.B., V.K.M, A.D., M.R., K.W.K. and C.B.(2) were responsible for the characterization measurements. R.H.L., G.W. and X.H.C. prepared the samples.

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Correspondence to A. J. Drew or C. Bernhard.

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