Superconductivity at 43 K at ambient pressure in the iron-based layered compound La1-xYxFeAsOy

Effect of Y substitution on the La-based iron oxypnictide superconductor LaFeAsO0.6 is studied. Replacement of La3+ (1.16 A) by smaller Y3+ (1.019 A) in a form of La1-xYxFeAsO0.6 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 LaFeAsO1-xFx under high pressure. The present results provide an alternative and much simpler way to achieve higher T-c in the La-based oxypnictide superconductors.