Antiferromagnetic spin correlations in the tetragonal phase of CaFe$_{2}$As$_{2}$

ORAL

Abstract

We present neutron scattering measurements of magnetic excitations in the tetragonal phase of CaFe$_{2}$As$_{2}$. Below $T_{S}$ = 173 K, CaFe$_{2}$As$_{2}$ undergoes a first-order transition to an orthorhombic structure with columnar antiferromagnetic ordering with a wavevector \textbf{Q}$_{AFM}$ = (101). This phase is characterized by strong magnetic interactions giving rise to steep spin waves. In the tetragonal phase above $T_{S}$, broad quasi-elastic excitations are observed near \textbf{Q}$_{AFM}$ that display a weak dependence on $L$, indicating two-dimensional antiferromagnetic correlations. These correlations are observed to persist up excitation energies of $\sim $50 meV and temperatures of at least 300 K. Our results indicate that strong magnetic interactions exist above $T_{S}$, and ordering is likely suppressed by magnetic frustration.

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Authors

  • R.J. McQueeney

    Ames Laboratory and Physics Department and Astronomy, Iowa State University, Ames, IA, Ames Laboratory and Iowa State University, Ames Laboratory, US DOE and Iowa State University, Ames Laboratory, Ames Laboratory/Department of Physics and Astronomy

  • S.O. Diallo

    Ames Laboratory, US DOE and Iowa State University

  • J.L. Zarestky

    Ames Laboratory and Physics Department and Astronomy, Iowa State University, Ames, IA, Ames Laboratory, US DOE and Iowa State University

  • Collin Broholm

    Johns Hopkins University

  • T.G. Perring

    Rutherford Appleton Laboratory

  • S.L. Bud'ko

    Ames Laboratory and Iowa State University, Ames Laboratory and Physics Department and Astronomy, Iowa State University, Ames, IA, Ames Laboratory, Ames Laboratory, US DOE and Iowa State University, Ames Laboratory/Iowa State University, Ames Laboratory/Department of Physics and Astronomy, Ames laboratory

  • N. Ni

    Ames Laboratory and Iowa State University, Ames Laboratory and Physics Department and Astronomy, Iowa State University, Ames, IA, Ames Lab / Iowa State University, Ames Laboratory, US DOE and Iowa State University, Iowa State University, Ames Laboratory/Department of Physics and Astronomy

  • Andreas Kreyssig

    Ames Laboratory and Physics Department and Astronomy, Iowa State University, Ames, IA, Ames Laboratory and Iowa State University, Ames Laboratory, US DOE and Iowa State University, Ames Laboratory/Department of Physics and Astronomy, Ames Laboratory, US DOE, Iowa State University, Ames, IA 5001, USA

  • P.C. Canfield

    Ames Laboratory and Department of Physics and Astronomy, Iowa State Univeristy, Ames, Iowa 50011, Ames Laboratory and Iowa State University, Ames Laboratory and Physics Department and Astronomy, Iowa State University, Ames, IA, Ames Laboratory, Ames Laboratory, US DOE and Iowa State University, Ames Laboratory/Department of Physics and Astronomy, Ames Lab / Iowa State University, Ames Laboratory/Iowa State University

  • Alan Goldman

    Ames Laboratory and Physics Department and Astronomy, Iowa State University, Ames, IA, Ames Laboratory and Iowa State University, Ames Laboratory, US DOE and Iowa State University, Ames Laboratory, Ames Loboratory, US DOE and Iowa State University, Ames Laboratory/Department of Physics and Astronomy, Ames Laboratory, US DOE, Iowa State University, Ames, IA 5001, USA