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

Journal article

We report heat capacity measurements of the pnictide materials SmFeAsO 1-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 y 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. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Authors: Baker, P; Giblin, SR; Pratt, F; Liu, R; Wu, G

• Publication status: Published
• Journal: NEW JOURNAL OF PHYSICS
• Volume: 11
• Issue: 2
• Pages: 025010-025010
• Publication date: 2009-02-27
• DOI: 10.1088/1367-2630/11/2/025010
• EISSN: 1367-2630
• ISSN: 1367-2630
• Language: English