Effect of substitution of Ca2+ for Eu2+ on pressure-induced superconductivity in EuFe2As2

Abstract

To elucidate competition between the Fe-based superconductivity and the antiferromagnetic order of Eu2+, the electrical resistivity of Eu0.85Ca0.15Fe2As2 under high pressure is presented. Under ambient pressure, the Fe-based spin-density-wave (SDW) transition and the antiferromagnetic ordering (AFM) of Eu2+ are observed at TSDW = 190 K and TN = 17 K, respectively. With applying pressure, the Fe-based superconductivity with Tc ∼ 25 K appears above 1.5 GPa, accompanying collapse of the SDW transition. Compared with EuFe2As2, Tc is close to T N, which implies strong competition between the superconductivity and the AFM. This competition would lead to non-zero resistivity at lowest temperature. © 2011 The Physical Society of Japan.