Superconductivity at 43 K at ambient pressure in the iron-based layered compoundLa1−xYxFeAsOy

Abstract

Effect of Y substitution on the La-based iron oxypnictide superconductor ${\text{LaFeAsO}}_{0.6}$ is studied. Replacement of ${\text{La}}^{3+}$ $(1.16\text{ }\text{\AA{}})$ by smaller ${\text{Y}}^{3+}$ $(1.019\text{ }\text{\AA{}})$ in a form of ${\text{La}}_{1\ensuremath{-}x}{\text{Y}}_{x}{\text{FeAsO}}_{0.6}$ results in the decrease in lattice parameters, which likely causes pressure effect into the system. Superconducting transition temperature $({T}_{c})$ increases monotonically with $x$, eventually up to 43.1 K for $x=0.5$. This ${T}_{c}$ is comparable to the highest ${T}_{c}$ reported for Y-free F-doped ${\text{LaFeAsO}}_{1\ensuremath{-}x}{\text{F}}_{x}$ under high pressure. The present results provide an alternative and much simpler way to achieve higher ${T}_{c}$ in the La-based oxypnictide superconductors.