To clarify competition between FeAs-based superconductivity and antiferromagnetism of Eu2+, and the superconducting properties in EuFe2As2, we investigated a Ca-substituted sample, Eu 0.5Ca0.5Fe2As2, under high pressure. Under ambient pressure, the sample exhibits a spin-density-wave (SDW) transition at TSDW = 191K and antiferromagnetic order at T N = 4K, but no evidence of superconductivity down to 2 K. The Ca-substitution certainly weakens the antiferromagnetism. With increasing pressure, TSDW shifts to lower temperature and becomes more unclear. Above 1.27 GPa, pressure-induced superconductivity with zero resistivity is observed at around Tc = 20K. At 2.14 GPa, Tc 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 EuFe 2As2.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)