Reentrant superconductivity in Eu(Fe_1−xIr_x)₂As₂

Abstract

The interplay between superconductivity and Eu(2+) magnetic ordering in Eu(Fe1-xIrx)2As2 is studied by means of electrical transport and magnetic measurements. For the near optimally doped sample Eu(Fe0.86Ir0.14)2As2, we witnessed two distinct transitions: a superconducting transition below 22.6 K which is followed by a resistivity reentrance caused by the ordering of the Eu(2+) moments. Further, the low field magnetization measurements show a prominent diamagnetic signal due to superconductivity, which is remarkable in the presence of a large-moment magnetically ordered system. The electronic structure for 12.5% Ir doped EuFe1.75Ir0.25As2 is investigated along with the parent compound EuFe2As2. As compared to EuFe2As2, the doped compound has an effectively lower value of density of states throughout the energy scale with a more extended bandwidth and stronger hybridization involving Ir. Shifting of the Fermi energy and a change in band filling in EuFe1.75Ir0.25As2 with respect to the pure compound indicate electron doping in the system.