Low-temperature thermal expansion of pure and inert-gas-doped fullerite C60

The low-temperature (2–24 K) thermal expansion of pure (single-crystal and polycrystalline) C60 and polycrystalline C60 intercalated with He, Ne, Ar, and Kr is investigated using a high-resolution capacitance dilatometer. The investigation of the time dependence of the sample length variations ΔL(t)...

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Veröffentlicht in:Fizika nizkih temperatur (Kiev) 2003, Vol.29 (4), p.324-332
Hauptverfasser: Aleksandrovskii, A. N., Dolbin, A. V., Esel’son, V. B., Gavrilko, V. G., Manzhelii, V. G., Udovidchenko, B. G., Bakai, A. S., Gadd, G. E., Moricca, S., Sundqvist, B.
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Sprache:eng
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Zusammenfassung:The low-temperature (2–24 K) thermal expansion of pure (single-crystal and polycrystalline) C60 and polycrystalline C60 intercalated with He, Ne, Ar, and Kr is investigated using a high-resolution capacitance dilatometer. The investigation of the time dependence of the sample length variations ΔL(t) on heating by ΔT shows that the thermal expansion is determined by the sum of positive and negative contributions, which have different relaxation times. The negative thermal expansion usually prevails at helium temperatures. The positive expansion is connected with the phonon thermalization of the system. The negative expansion is caused by reorientation of the C60 molecules. It is assumed that the reorientation is of a quantum character. The inert gas impurities affect the reorientation of the C60 molecules very strongly, especially at liquid-helium temperatures. A temperature hysteresis of the thermal expansion coefficient of Kr– and He–C60 solutions is revealed. The hysteresis is attributed to orientational polymorphous transformation in these systems.
ISSN:1063-777X
0132-6414
1090-6517
DOI:10.1063/1.1542477