High-pressure Raman study of the Sm_2.75C₆₀ fulleride

Abstract

The high-pressure response of the Sm_2.75C₆₀ fulleride is probed by Raman spectroscopy. The Raman spectrum of Sm_2.75C₆₀ and its pressure evolution differ significantly from those of pristine C₆₀. The initial well-resolved Raman spectrum of the fulleride disappears above 4 GPa. This change is reversible; however, the original low-pressure Raman profiles are recovered only below 2 GPa. These observations are in line with the pressure-induced hysteretic phase transition of the compound observed earlier by X-ray diffraction and the proposed insulator to metal transition.

Keywords:

• rare earth fullerides
• valence transition
• high pressure
• Raman spectroscopy

Acknowledgements

This work was partly supported by the Hellenic Ministry of National Education and Religious Affairs and the European Union through the “Pythagoras II” program, and by the EPSRC (EP/G037949/1). The financial support of a M. Curie reintegration grant (MERG-CT-2004-513606) to J.A. is also acknowledged.