Superconductivity at 41.0 K in the F-doped LaFeAsO1-xFx

Here we report the enhanced superconductivity in the LaFeAsO1-xFx system prepared by high pressure synthesis. The highest onset superconducting transition temperature (T-C) in this La-based system is 41.0 K with the nominal composition of LaFeAsO1-xFx (x = 0.6), which is higher than that reported previously by ambient pressure synthesis. The increase of T-C can be attributed to further shrinkage of the crystal lattice that causes stronger chemical pressure on the Fe-As plane, which is induced by the increased F-doping level under the high pressure synthesis. (C) 2008 Elsevier Ltd. All rights reserved.