Pressure-Induced Superconductivity in Eu0.5Ca0.5Fe2As2: Wide Zero-Resistivity Region Due to Suppression of Eu Magnetic Order and Chemical Pressure

概要

論文の詳細を見る
To clarify competition between FeAs-based superconductivity and antiferromagnetism of Eu2+, and the superconducting properties in EuFe2As2, we investigated a Ca-substituted sample, Eu0.5Ca0.5Fe2As2, under high pressure. Under ambient pressure, the sample exhibits a spin-density-wave (SDW) transition at $T_{\text{SDW}}=191$ K and antiferromagnetic order at $T_{\text{N}}=4$ K, but no evidence of superconductivity down to 2 K. The Ca-substitution certainly weakens the antiferromagnetism. With increasing pressure, $T_{\text{SDW}}$ shifts to lower temperature and becomes more unclear. Above 1.27 GPa, pressure-induced superconductivity with zero resistivity is observed at around $T_{\text{c}}=20$ K. At 2.14 GPa, $T_{\text{c}}$ reaches a maximum value of 24 K and the superconducting transition becomes sharpest. The chemical pressure and the suppression of Eu magnetic order induced by Ca substitution enlarge the zero resistivity region compared to pure EuFe2As2.
2010-07-15