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# Magnetism and its microscopic origin in iron-based high-temperature superconductors

## Abstract

High-temperature superconductivity in the iron-based materials emerges from, or sometimes coexists with, their metallic or insulating parent compound states. This is surprising, as these undoped states exhibit dramatically different antiferromagnetic spin arrangements and Néel temperatures. Although there is a general consensus that magnetic interactions are important for superconductivity, much remains unknown concerning the microscopic origin of the magnetic states. In this review, we summarize the progress in this area, focusing on recent experimental and theoretical results, and their microscopic implications. We conclude that the parent compounds are in a state that is more complex than that implied by a simple Fermi surface nesting scenario, and a dual description including both itinerant and localized degrees of freedom is needed to properly describe these fascinating materials.

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## Acknowledgements

We thank L. W. Harriger for preparing the figures shown in this manuscript. We are also grateful to T. A. Maier for calculating the FSs of BaFe2As2 shown in Fig. 2d. P.D. is supported by the US NSF DMR-1063866 (neutron scattering studies on electron-doped iron pnictides), OISE-0968226 (international collaboration) and by US DOE, BES, under Grant No. DE-FG02-05ER46202 (single crystal growth at UTK and neutron scattering studies of hole-doped iron pnictides and other iron-based superconductors). Work at Institute of Physics is supported by the Ministry of Science and Technology of China 973 program (2012CB821400). E.D. is supported by the US DOE, BES, Materials Sciences and Engineering Division and by the US NSF DMR-11-04386.

## Affiliations

1. ### Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA

• Pengcheng Dai
•  & Elbio Dagotto
2. ### Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, PO Box 603, Beijing 100190, China

• Pengcheng Dai
•  & Jiangping Hu
3. ### Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA

• Jiangping Hu
4. ### Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

• Elbio Dagotto

## Authors

### Contributions

P.D. and E.D. wrote the experimental and theoretical portions of the article, respectively. J.P.H. revised the article. All authors discussed the outline of the article.

### Competing interests

The authors declare no competing financial interests.

## Corresponding authors

Correspondence to Pengcheng Dai or Elbio Dagotto.

### DOI

https://doi.org/10.1038/nphys2438

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