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

• DOI: 10.1038/nmat2396
• Publication Date: 2009-02-22T18:04:21Z
• Authors: A. J. Drew; Ch. Niedermayer; P. J. Baker; F. L. Pratt; S. J. Blundell; T. Lancaster; R. H. Liu; G. Wu; X. H. Chen; I. Watanabe; V. K. Malik; A. Dubroka; M. Rössle; K. W. Kim; C. Baines; C. Bernhard
• Keywords: Muon spin spectroscopy; Magnetism; Mott insulator; Pnictogen

The recent observation of superconductivity with critical temperatures up to 55 K in the FeAs based pnictide compounds marks the first discovery of a non copper-oxide based layered high-Tc superconductor (HTSC) [1-3]. It has raised the suspicion that these new materials share a similar pairing mechanism to the cuprates, since both exhibit superconductivity following charge doping of a magnetic parent material. Here we present a muon spin rotation study on SmFeAsO1-xFx (x=0-0.30), which shows that static magnetism persists well into the superconducting regime. The analogy with the cuprates is quite surprising since the parent compounds appear to have different magnetic ground states: itinerant spin density wave for the pnictides contrasted with the Mott-Hubbard insulator in the cuprates. Our findings suggest that proximity to magnetic order and associated soft magnetic fluctuations, rather than the strong electronic correlations in the vicinity of a Mott-Hubbard-metal-to-insulator transition, may be the key ingredients of HTSC.<br/>Accepted in Nature Materials<br/>