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 LaFeAsO_0.6 is studied. Replacement of La³⁺ (1.16Å) by smaller Y³⁺ (1.019Å) in a form of La_1-xY_xFeAsO_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 LaFeAsO_1-xF_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.