Raman spectroscopy study of spin-orbital liquid candidate FeSc$_2$S$_4$

ORAL

Abstract

The A-site cubic spinel FeSc$_2$S$_4$, containing Fe$^{2+}$ ions in a tetrahedral S$_4$ environment, represents a rare candidate of a spin-orbital liquid, where spin and orbital order remain suppressed down to the lowest measurable temperature [1]. We studied phonon spectrum and orbital excitations in FeSc$_2$S$_4$ by Raman spectroscopy on single crystals. At temperatures below 100K we observe widening of sulfur 330 cm$^{-1}$ T$_{2g}$ and 365 cm$^{-1}$ A$_{1g}$ phonon modes with an additional weak mode emerging at 400 cm$^{-1}$. These changes can indicate weak lattice distortions associated with the sulfur sites. Below 100K we also observe orbital excitations at frequencies of approximately 2000 cm$^{-1}$. We discuss the result in terms of a competition of spin-orbital liquid and a magnetically ordered state. [1] L. Mittelstadt et al., Phys. Rev. B 91 125112 (2015).

*The work at IQM was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Material Sciences and Engineering, under Grant No. DEFG02-08ER46544.

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Authors

  • Streit Cunningham

    • Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland, USA

  • K.W. Plumb

    • Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland, USA

  • J.R. Morey

    • Department of Chemistry, Johns Hopkins University, Baltimore, Maryland, USA

  • T.M. McQueen

    • Department of Chemistry, Johns Hopkins University, Baltimore, Maryland, USA

  • S. Koohpayeh

    • Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland, USA

  • C.L. Broholm

    • Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland, USA

  • Natalia Drichko

    • Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland, USA