paper

Thermodynamic properties of Ba1-xMxFe2As2 (M = La and K)

arXiv:0806.3573 · doi:10.1088/1367-2630/10/12/123031

Abstract

The specific heat $C (T)$ of BaFe $_{2}$ As $_{2}$ single crystal, electron-doped Ba $_{0.7}$ La $_{0.3}$ Fe $_{2}$ As $_{2}$ and hole-doped Ba $_{0.5}$ K $_{0.5}$ Fe $_{2}$ As $_{2}$ polycrystals were measured. For undoped BaFe $_{2}$ As $_{2}$ single crystal, a very sharp specific heat peak was observed at 136 K. This is attributed to the structural and antiferromagnetic transitions occurring at the same temperature. $C (T)$ of the electron-doped non-superconducting Ba $_{0.7}$ La $_{0.3}$ Fe $_{2}$ As $_{2}$ also shows a small peak at 120 K, indicating a similar but weaker structural/antiferromagnetic transition. For the hole-doped superconducting Ba $_{0.5}$ K $_{0.5}$ Fe $_{2}$ As $_{2}$ , a clear peak of $C / T$ was observed at $T_{c}$ = 36 K, which is the highest peak seen at superconducting transition for iron-based high- $T_{c}$ superconductors so far. The electronic specific heat coefficient $I^^{3}$ and Debye temperature $I^_{D}$ of these compounds were obtained from the low temperature data.