Superconductivity and phase diagram in iron-based arsenic-oxides ReFeAsO1-δ (Re = rare-earth metal) without fluorine doping

Here we report a new class of superconductors prepared by high-pressure synthesis in the quaternary family ReFeAsO(1-delta) (Re = Sm, Nd, Pr, Ce, La) without fluorine doping. The onset superconducting critical temperature (T(c)) in these compounds increases with the reduction of the Re atom size, and the highest T(c) obtained so far is 55K in SmFeAsO(1-delta). For the NdFeAsO(1-delta) compound with different oxygen concentration a dome-shaped phase diagram was found. Copyright (c) EPLA, 2008.