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Consistent model of magnetism in ferropnictides

Nature Physics volume 7, pages 485–489 (2011)Cite this article

Abstract

The discovery of superconductivity in LaFeAsO introduced ferropnictides as a new class of superconducting compounds with critical temperatures second only to those of the cuprates. Although the presence of iron makes the ferropnictides radically different from the cuprates, antiferromagnetism in the parent compounds suggests that superconductivity and magnetism are interrelated in both of them. However, the character of magnetic interactions and spin fluctuations in ferropnictides is not reasonably described by conventional models of magnetism. Here we show that the most puzzling features can be naturally reconciled within a rather simple effective spin model with a biquadratic interaction, which is consistent with electronic structure calculations. By going beyond the Heisenberg model, our description explains numerous experimental observations, including the peculiarities of the spin-wave spectrum, thin domain walls and crossover from a first- to second-order phase transition under doping. The model also offers insight into the occurrence of the nematic phase above the antiferromagnetic phase transition.

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Figure 1: Effect of the biquadratic coupling on the spin-wave spectrum.
Figure 2: Phase diagram.
Figure 3: Evidence of the nematic phase.

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Acknowledgements

We are grateful to S. L. Bud’ko and D. S. Inosov for fruitful discussions, and to I. I. Mazin for critical reading of the manuscript and useful comments. Work at UNL was supported by NSF DMR-1005642 and EPS-1010674. Work at Ames Laboratory was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering, under Contract No. DE-AC02-07CH11358. K.D.B. is a Cottrell Scholar of Research Corporation.

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Authors and Affiliations

  1. Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA

    Aleksander L. Wysocki & Kirill D. Belashchenko

  2. Ames Laboratory, Ames, Iowa 50011, USA

    Vladimir P. Antropov

Authors
  1. Aleksander L. Wysocki
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  2. Kirill D. Belashchenko
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  3. Vladimir P. Antropov
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Contributions

A.L.W. carried out the thermodynamic calculations and analysed the results with K.D.B. K.D.B. and V.P.A. designed the study, carried out the spin-wave analysis and wrote the paper. All authors discussed the results.

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Correspondence to Kirill D. Belashchenko.

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The authors declare no competing financial interests.

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Wysocki, A., Belashchenko, K. & Antropov, V. Consistent model of magnetism in ferropnictides. Nature Phys 7, 485–489 (2011). https://doi.org/10.1038/nphys1933

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