Reentrant Superconductivity in Ir-doped Eu(Fe1-xIrx)2As2

The interplay between superconductivity and Eu$^2+$ magnetic ordering in Eu(Fe$_1-x$Ir$_x$)$_2$As$_2$ is studied by means of electrical transport and magnetic measurements. For the critically doped sample Eu(Fe$_0.86$Ir$_0.14$)$_2$As$_2$, 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 presence of a large moment magnetically ordered system. The electronic structure for a 12.5% Ir doped EuFe$_1.75$Ir$_0.25$As$_2$ is investigated along with the parent compound EuFe$_2$As$_2$. As compared to EuFe$_2$As$_2$, the doped compound has effectively lower value of density of states throughout the energy scale with more extended bandwidth and stronger hybridization involving Ir. Shifting of Fermi energy and change in band filling in EuFe$_1.75$Ir$_0.25$As$_2$ with respect to the pure compound indicate electron doping in the system.