# Heat capacity measurements on FeAs-based compounds: a thermodynamic probe of electronic and magnetic states - Condensed Matter > Superconductivity

Heat capacity measurements on FeAs-based compounds: a thermodynamic probe of electronic and magnetic states - Condensed Matter > Superconductivity - Download this document for free, or read online. Document in PDF available to download.

Abstract: We report heat capacity measurements of the pnictide materialsSmFeAsO${1-x}$F$x$, NdFeAsO, LaFeAsO${1-x}$F$x$ and LiFeAs. ForSmFeAsO${1-x}$F$x$, with x close to 0.1, we use 3 He measurements todemonstrate a transfer of entropy from the peak at TN to a previouslyunidentified ~2 K feature which grows with increasing doping. Our results onthe Sm samples are compared with a similarly doped La sample to elucidate thecrystal field levels of the Sm3+ ion at 0, 23, and 56 meV which lead to aSchottky-like anomaly, and also show that there is a significant increase inthe Sommerfeld coefficient $\gamma$ when La is replaced by Sm or Nd. Thelattice contribution to the heat capacity of the superconducting oxypnictidesis found to vary negligibly with chemical substitution. We also present a heatcapacity measurement of LiFeAs showing the feature at Tc, which issignificantly rounded and much smaller than the BCS value.

Author: P.J. Baker, S.R. Giblin, F.L. Pratt, R.H. Liu, G. Wu, X.H. Chen, M.J. Pitcher, D.R. Parker, S.J. Clarke, S.J. Blundell

Source: https://arxiv.org/