Raman scattering study of rare-earth hexaboride

The excitation-energy, polarization, pressure, and temperature dependences of Raman scattering spectra have been measured for the RB 6 crystals ( R = Ca 2 + , La 3 + , Ce 3 + , Pr 3 + , Sm 2.6 + , Gd 3 + , Dy 3 + , and Yb 2 + ). In the Raman spectra, the extra peaks have been clearly observed at aro...

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Bibliographic Details
Published in:Physica. B, Condensed matter Condensed matter, 2005-04, Vol.359, p.941-943
Main Authors: Ogita, N., Nagai, S., Udagawa, M., Iga, F., Sera, M., Oguchi, T., Akimitsu, J., Kunii, S.
Format: Article
Language:English
Subjects:
Raman scattering
Rare-earth hexaboride
Valence change
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Summary:The excitation-energy, polarization, pressure, and temperature dependences of Raman scattering spectra have been measured for the RB 6 crystals ( R = Ca 2 + , La 3 + , Ce 3 + , Pr 3 + , Sm 2.6 + , Gd 3 + , Dy 3 + , and Yb 2 + ). In the Raman spectra, the extra peaks have been clearly observed at around 200 cm - 1 , except for the Raman-active phonons and CEF excitations. The extra peaks show anomalous behavior in the temperature, polarization, and lattice parameter dependences. These anomalous behaviors originate from the vibration of the rare-earth ions in octahedral B 6 cage, and the extra peaks can be assigned as the second-order Raman excitations of T 1 u phonon at Brillouin zone boundary. In the results of pressure dependence, the valence of all Sm ions in SmB 6 becomes trivalent above 20 GPa at room temperature.
ISSN:0921-4526
DOI:10.1016/j.physb.2005.01.270