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تسجيل مستخدم جديد$mu$SR and Neutron Diffraction Investigations on Reentrant Ferromagnetic Superconductor Eu(Fe{0.86}Ir{0.14})2As2
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Results of muon spin relaxation ($mu$SR) and neutron powder diffraction measurements on a reentrant superconductor Eu(Fe$_{0.86}$Ir$_{0.14}$)$_2$As$_2$ are presented. Eu(Fe$_{0.86}$Ir$_{0.14}$)$_2$As$_2$ exhibits superconductivity at $T_{rm c,on} approx 22.5$~K competing with long range ordered Eu$^{+2}$ moments below $approx 18$ K. A reentrant behavior (manifested by nonzero resistivity in the temperature range 10--17.5 K) results from an exquisite competition between the superconductivity and magnetic order. The zero field $mu$SR data confirm the long range magnetic ordering below $T_{rm Eu} = 18.7(2)$ K. The transition temperature is found to increase with increasing magnetic field in longitudinal field $mu$SR which along with the neutron diffraction results, suggests the transition to be ferromagnetic. The neutron diffraction data reveal a clear presence of magnetic Bragg peaks below $T_{rm Eu}$ which could be indexed with propagation vector k = (0, 0, 0), confirming a long range magnetic ordering in agreement with $mu$SR data. Our analysis of the magnetic structure reveals an ordered magnetic moment of $6.29(5),mu_{rm B}$ (at 1.8 K) on the Eu atoms and they form a ferromagnetic structure with moments aligned along the $c$-axis. No change in the magnetic structure is observed in the reentrant or superconducting phases and the magnetic structure remains same for 1.8 K $leq T leq T_{rm Eu}$. No clear evidence of structural transition or Fe moment ordering was found.
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_{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.
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