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Valence fluctuation in CeMo2Si2C


Burkhardt,  U.
Ulrich Burkhardt, Chemical Metal Science, Max Planck Institute for Chemical Physics of Solids, Max Planck Society;

Geibel,  C.
Christoph Geibel, Physics of Quantum Materials, Max Planck Institute for Chemical Physics of Solids, Max Planck Society;

Hossain,  Z.
Physics of Quantum Materials, Max Planck Institute for Chemical Physics of Solids, Max Planck Society;

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Paramanik, U. B., Anupam, A., Burkhardt, U., Prasad, R., Geibel, C., & Hossain, Z. (2013). Valence fluctuation in CeMo2Si2C. Journal of Alloys and Compounds, 580, 435-441. doi:10.1016/j.jallcom.2013.05.169.

We report on the valence fluctuation of Ce in CeMo2Si2C as studied by means of magnetic susceptibility chi(T), specific heat C(T), electrical resistivity rho(T) and X-ray absorption spectroscopy. Powder X-ray diffraction revealed that CeMo2Si2C crystallizes in CeCr2Si2C-type layered tetragonal crystal structure (space group P4/mmm). The unit cell volume of CeMo2Si2C deviates from the expected lanthanide contraction, indicating non-trivalent state of Ce ions in this compound. The observed weak temperature dependence of the magnetic susceptibility and its low value indicate that Ce ions are in valence fluctuating state. The formal L-III Ce valence in CeMo2Si2C((v) over tilde similar or equal to 3: 14 as determined from X-ray absorption spectroscopy measurement is well below the value ((v) over tilde) similar or equal to 3.4 in tetravalent Ce compound CeO2. The temperature dependence of specific heat does not show any anomaly down to 1.8 K which rules out any magnetic ordering in the system. The Sommerfeld coefficient obtained from the specific heat data is gamma = 23.4 mJ/mol K-2. The electrical resistivity follows the T-2 behavior in the low temperature range below 35 K confirming a Fermi liquid behavior. Accordingly both the Kadowaki Woods ratio A/gamma(2) and the Sommerfeld Wilson ratio chi(0)/gamma are in the range expected for Fermi-liquid systems. In order to get some information on the electronic states, we calculated the band structure within the density functional theory, even-though this approach is not able to treat 4f electrons accurately. The non-f electron states crossing the Fermi level have mostly Mo 4d character. They provide the states with which the 4f sates are strongly hybridized, leading to the intermediate valent state. (C) 2013 Elsevier B.V. All rights reserved.