Raman Scattering Study of the Low Temperature, High Pressure Structural Transition in CoV2O4

ORAL

Abstract

At ambient pressures, CoV2O4 exists very near a critical value of the vanadium-vanadium separation, rV-V = 2.94 Å, for the AV2O4 spinels, below which the electronic character transitions from insulating or semiconducting to metallic. CoV2O4 has not been shown to undergo a symmetry lowering phase change at low temperatures, unlike most other AV2O4 spinels. The cubic structure has been predicted to be stable at high pressures, despite well-known strong coupling between spin, lattice, and electronic degrees of freedom in spinels. We studied the triply degenerate 192 cm-1 phonon mode with Raman spectroscopy to determine if the cubic phase remains stable at low temperatures and if there is a structural phase change associated with the pressure-induced semiconductor-metal transition. We find no evidence for a structural transition at low temperatures at ambient pressure. However, at low temperatures and above P~4 GPa, we observe a splitting of the phonon mode, indicative of a lower symmetry phase near the semiconductor-metal phase boundary. These results provide evidence that strong spin-lattice coupling plays an essential role in the pressure-tuned semiconductor-metal transition of CoV2O4.

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Presenters

  • John Slimak

    Physics and Frederick Seitz Materials Research Laboratory, Univ of Illinois - Urbana, Dept. of Physics and Materials Research Laboratory, University of Illinois, Urbana-Champaign

Authors

  • John Slimak

    Physics and Frederick Seitz Materials Research Laboratory, Univ of Illinois - Urbana, Dept. of Physics and Materials Research Laboratory, University of Illinois, Urbana-Champaign

  • Taylor Byrum

    Physics and Frederick Seitz Materials Research Laboratory, Univ of Illinois - Urbana, Dept. of Physics and Materials Research Laboratory, University of Illinois, Urbana-Champaign

  • Astha Sethi

    Physics and Frederick Seitz Materials Research Laboratory, Univ of Illinois - Urbana, Dept. of Physics and Materials Research Laboratory, University of Illinois, Urbana-Champaign

  • Haidong Zhou

    Physics and Astronomy, Univ of Tennessee, Knoxville, Physics and Astronomy, University of Tennessee Knoxville, Department of Physics and Astronomy, University of Tennessee, Department of Physics and Astronomy, University of Tennessee Knoxville, Department of Physics & Astronomy, University of Tennessee, University of Tennessee, Physics and Astronomy, University of Tennessee, Physics, University of Tennessee, Univ of Tennessee, Knoxville, Physics and Astronomy, University of Tennessee, knoxville, Dept. of Physics and Astronomy, University of Tennessee

  • Lance Cooper

    Physics and Frederick Seitz Materials Research Laboratory, Univ of Illinois - Urbana, Dept. of Physics and Materials Research Laboratory, University of Illinois, Urbana-Champaign, University of Illinois Urbana-Champaign