Structural and physical properties ofSmFe1−xIrxAsO(0≤x≤0.275)obtained by synchrotron x-ray diffraction, Raman spectroscopy, and magnetization measurements

Abstract

In this paper we have carefully investigated the structural and physical properties of the ${\text{SmFe}}_{1\ensuremath{-}x}{\text{Ir}}_{x}\text{AsO}$ solid solution $(0\ensuremath{\le}x\ensuremath{\le}0.275)$, chosen as a case study, by means of synchrotron x-ray diffraction, Raman spectroscopy, and magnetization measurements. Our data confirm the positive role of doping in terms of insurgence of superconductivity for $x\ensuremath{\ge}0.06$. Increasing of doping leads to the disappearance of superconductivity while preserving the tetragonal structure and As-Fe(Ir)-As bond angles within the range where superconductivity should be observed. The set of data collected in this paper have been used together with available literature results on similar transition-metal-doped $\mathit{RE}\text{FeAsO}$ ($\mathit{RE}=\text{rare earth}$) compounds in order to try to understand and explain the peculiar behavior of these phases and their phase diagrams. We provided a solid explanation of the observed trends and features by considering the compressibility along the $c$ axis of the crystal structure as the key parameter in transition-metals-doped iron pnictides.