Heat capacity measurements on FeAs-based compounds: a thermodynamic probe of electronic and magnetic states
| Autor: | Baker, P. J., Giblin, S. R., Pratt, F. L., Liu, R. H., Wu, G., Chen, X. H., Pitcher, M. J., Parker, D. R., Clarke, S. J., Blundell, S. J. |
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| Rok vydání: | 2008 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1088/1367-2630/11/2/025010 |
| Popis: | We report heat capacity measurements of the pnictide materials SmFeAsO$_{1-x}$F$_x$, NdFeAsO, LaFeAsO$_{1-x}$F$_x$ and LiFeAs. For SmFeAsO$_{1-x}$F$_x$, with x close to 0.1, we use 3 He measurements to demonstrate a transfer of entropy from the peak at TN to a previously unidentified ~2 K feature which grows with increasing doping. Our results on the Sm samples are compared with a similarly doped La sample to elucidate the crystal field levels of the Sm3+ ion at 0, 23, and 56 meV which lead to a Schottky-like anomaly, and also show that there is a significant increase in the Sommerfeld coefficient $\gamma$ when La is replaced by Sm or Nd. The lattice contribution to the heat capacity of the superconducting oxypnictides is found to vary negligibly with chemical substitution. We also present a heat capacity measurement of LiFeAs showing the feature at Tc, which is significantly rounded and much smaller than the BCS value. Comment: 11 pages, 4 figures, submitted to New Journal of Physics focus issue on Iron-Based Superconductors |
| Databáze: | arXiv |
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