Superconductivity at 25K in hole-doped (La1-xSr4x) OFeAs

By partially substituting the tri-valence element La with di-valence element Sr in LaOFeAs, we introduced holes into the system. For the first time, we successfully synthesized the hole-doped new superconductors (La1-xSrx) OFeAs. The maximum superconducting transition temperature at about 25K was observed at a doping level of x=0.13. It is evidenced by Hall effect measurements that the conduction in this type of material is dominated by hole-like charge carriers, rather than electron-like ones. Together with the data of the electron-doped system La(O1-xFx) FeAs, a generic phase diagram is depicted and is revealed to be similar to that of the cuprate superconductors. Copyright (c) EPLA, 2008.