Bulk properties of : A question of zero thermal expansionKwang-hyun Jang1, Wan Young Song1, 2, J.-G. Park1, 2, H. C. Kim3, A. Lindbaum4, H. Müller4 and E. Bauer4
1 Department of Physics and Institute of Basic Science, Sungkyunkwan University Suwon 440-746, Korea
2 Center for Strongly Correlated Materials Research, Seoul National University Seoul 151-742, Korea
3 Material Science Laboratory, Korea Basic Science Institute - Daejon 305-333, Korea
4 Institute of Solid State Physics, Vienna University of Technology A-1040 Wien, Austria
received 28 January 2004; accepted in final form 26 October 2004
published online 8 December 2004
Despite the recent report of zero thermal expansion in , our extensive studies of the physical properties of pure failed to find anomalous behavior of the thermal expansion of both X-ray and dilatometry measurements. Instead, the temperature dependence of the lattice constants can be simply explained in terms of the Debye model with the cutoff frequency of 226 , which was estimated from heat capacity measurement. Additionally, susceptibility measurements have not revealed any sign of a change of the valency from 2 to 700 , but magnetic correlations develop at low temperatures. Important findings of further interest are that has very strong low-lying optic phonons, 1.7 oscillator strength with an energy of 80 , and shows strong increase of Grüneisen parameter below 20 .
65.40.De - Thermal expansion; thermomechanical effects.
61.10.Nz - X-ray diffraction.
65.40.Ba - Heat capacity.
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