We report the realization of superconductivity by 5d element Ir doping in LaFeAsO, a prototype parent compound of high-temperature iron based superconductors. X-ray diffraction patterns indicate that the material has formed the ZrCuSiAs-type structure with a space group P4/nmm. The systematic evolution of the lattice constants demonstrated that the Fe ions were successfully replaced by the Ir. Both electrical resistance and magnetization measurements show superconductivity up to 11 K in LaFe1-xIrxAsO. The superconducting transitions at different magnetic fields were also measured yielding a slope of -dHc2/dT = 6.7 T / K near Tc, and the upper critical field at zero K is found to be about 55 T. This is the first example of bulk superconductivity induced by replacing the Fe sites with higher d-orbital electrons in FeAs-1111 family, which should add more ingredients to the underlying physics of the iron-based superconductors.
@article{arxiv.0904.0772,
title = {Superconductivity in Ir-doped LaFe1-xIrxAsO},
author = {Yanpeng Qi and Lei Wang and Zhaoshun Gao and Dongliang Wang and Xianping Zhang and Zhiyu Zhang and Yanwei Ma},
journal= {arXiv preprint arXiv:0904.0772},
year = {2009}
}