Anisotropic 2D Spin Fluctuations in Superconducting Ba(Fe$_{0.926}$Co$_{0.074}$)$_2$As$_2$

ORAL

Abstract

We report inelastic neutron scattering from superconducting Ba(Fe$_{0.926}$Co$_{0.074}$)$_2$As$_2$. For energies up to 150 meV, magnetic excitations are found close to the 2D antiferromagnetic (AFM) wavevector $\mathbf{Q}_{AFM} = $ (0.5 0.5) in the tetragonal symmetry of the parent compound BaFe$_2$As$_2$. We observe an anisotropy of the in-plane spin fluctuations, allowing an estimate of the effective AFM spin exchange interactions: $J_2/J_1 = 1.0 (3)$ ($J_1$: NN; $J_2$: NNN). The 8 meV spin resonance displays a similar in-plane anisotropy. Above 100 meV, the anisotropy evolves into two separated maxima displaced transverse to $\mathbf{Q}_{AFM}$. While the low energy results can be interpreted in terms of competing exchange interactions, the more complex high energy/wavevector dependence requires an itinerant model.

*Ames Laboratory is supported by the U.S. Department of Energy under Contract No. DE-AC02-07CH11358.

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Authors

  • M. Stone

    • Oak Ridge National Laboratory

  • Haifeng Li

    • Ames Laboratory and Department of Physics and Astronomy, Iowa State University

  • Collin Broholm

    • Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University

  • David Vaknin

    • Ames Laboratory and Department of Physics and Astronomy, Iowa State University

  • Daniel Pratt

    • Ames Laboratory and Department of Physics and Astronomy, Iowa State University

  • Wei Tian

    • Ames Laboratory and Department of Physics and Astronomy, Iowa State University

  • Ni Ni

  • D. Abernathy

    • Oak Ridge National Laboratory

  • Souleymane Diallo

    • Ames Laboratory and Department of Physics and Astronomy, Iowa State University

  • Jerel Zarestky

    • Ames Laboratory and Department of Physics and Astronomy, Iowa State University

  • Sergey Bud'ko

    • Ames Laboratory and Department of Physics and Astronomy, Iowa State University

  • Rafael Fernandes

    • Ames Laboratory and Department of Physics and Astronomy, Iowa State University

  • Paul Canfield

    • Ames Laboratory and Department of Physics and Astronomy, Iowa State University

  • Robert McQueeney

    • Ames Laboratory and Department of Physics and Astronomy, Iowa State University