Raman scattering study of hexaboride crystals

N. Ogita, S. Nagai, N. Okamoto, F. Iga, S. Kunii, Jun Akimitsu, M. Udagawa

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The valence-dependent Raman scattering spectra has been found for the RB6 crystals (R = Ca2+, Yb2+, Ce3+, Pr3+, Gd3+, and Dy3+). In the divalent crystals of CaB6 and YbB6, Eg phonon shows doublet, while the line shape is a broad single peak for the trivalent case. Since both doublet peaks satisfy the selection rule due to the cubic symmetry, the doublet spectra is not explained by the structural phase transition, but by the anisotropic charge distribution on B6. In the trivalent crystals, the two kind of the extra peaks have been commonly observed at around 200 cm-1 and at around 1400 cm-1. The peak intensities of the former decrease with decreasing temperature, and their peak energies increase with increasing lattice constant. These anomalous features are well explained by the vibration of R ion in the oversized cage space formed octahedral B6 molecule. Thus, this new excitation can be attributed to a local vibration of the R ion, which can be regarded as "rattler."

Original languageEnglish
Pages (from-to)131-134
Number of pages4
JournalPhysica B: Condensed Matter
Volume328
Issue number1-2
DOIs
Publication statusPublished - Apr 2003
Externally publishedYes

Fingerprint

Raman scattering
Raman spectra
Crystals
Ions
crystals
Charge distribution
Lattice constants
Phase transitions
vibration
Molecules
charge distribution
line shape
ions
valence
symmetry
Temperature
excitation
molecules
temperature
energy

Keywords

  • Hexaborides
  • Local vibration mode
  • Raman scattering

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics

Cite this

Ogita, N., Nagai, S., Okamoto, N., Iga, F., Kunii, S., Akimitsu, J., & Udagawa, M. (2003). Raman scattering study of hexaboride crystals. Physica B: Condensed Matter, 328(1-2), 131-134. https://doi.org/10.1016/S0921-4526(02)01827-6

Raman scattering study of hexaboride crystals. / Ogita, N.; Nagai, S.; Okamoto, N.; Iga, F.; Kunii, S.; Akimitsu, Jun; Udagawa, M.

In: Physica B: Condensed Matter, Vol. 328, No. 1-2, 04.2003, p. 131-134.

Research output: Contribution to journalArticle

Ogita, N, Nagai, S, Okamoto, N, Iga, F, Kunii, S, Akimitsu, J & Udagawa, M 2003, 'Raman scattering study of hexaboride crystals', Physica B: Condensed Matter, vol. 328, no. 1-2, pp. 131-134. https://doi.org/10.1016/S0921-4526(02)01827-6
Ogita, N. ; Nagai, S. ; Okamoto, N. ; Iga, F. ; Kunii, S. ; Akimitsu, Jun ; Udagawa, M. / Raman scattering study of hexaboride crystals. In: Physica B: Condensed Matter. 2003 ; Vol. 328, No. 1-2. pp. 131-134.
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AB - The valence-dependent Raman scattering spectra has been found for the RB6 crystals (R = Ca2+, Yb2+, Ce3+, Pr3+, Gd3+, and Dy3+). In the divalent crystals of CaB6 and YbB6, Eg phonon shows doublet, while the line shape is a broad single peak for the trivalent case. Since both doublet peaks satisfy the selection rule due to the cubic symmetry, the doublet spectra is not explained by the structural phase transition, but by the anisotropic charge distribution on B6. In the trivalent crystals, the two kind of the extra peaks have been commonly observed at around 200 cm-1 and at around 1400 cm-1. The peak intensities of the former decrease with decreasing temperature, and their peak energies increase with increasing lattice constant. These anomalous features are well explained by the vibration of R ion in the oversized cage space formed octahedral B6 molecule. Thus, this new excitation can be attributed to a local vibration of the R ion, which can be regarded as "rattler."

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