Heat capacity measurements on FeAs-based compounds: a thermodynamic probe of electronic and magnetic states

Baker, P. J., Giblin, Sean ORCID: https://orcid.org/0000-0003-1876-8619, Pratt, F. L., Liu, R. H., Wu, G., Chen, X. H., Pitcher, M. J., Parker, D. R., Clarke, S. J. and Blundell, S. J. 2009. Heat capacity measurements on FeAs-based compounds: a thermodynamic probe of electronic and magnetic states. New Journal of Physics 11 , 025010. 10.1088/1367-2630/11/2/025010

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Abstract

We report heat capacity measurements of the pnictide materials SmFeAsO1-xFx, NdFeAsO, LaFeAsO1-xFx and LiFeAs. For SmFeAsO1- xFx, with x close to 0.1, we use 3He 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, 20 and 45 meV, which lead to a Schottky-like anomaly, and also show that there is a significant increase in the Sommerfeld coefficient γ 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.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Subjects:	Q Science > QC Physics
Publisher:	IOP Publishing
ISSN:	1367-2630
Last Modified:	21 Oct 2022 10:50
URI:	https://orca.cardiff.ac.uk/id/eprint/41501

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