Through partial substitution of Sm by U in SmFeAsO, a different member of the family of iron-based superconductors was successfully synthesized. X-ray diffraction measurements show that the lattice constants along the a and c axes are both squeezed through U doping, indicating a successful substitution of U at the Sm site. The parent compound shows a strong resistivity anomaly near 150 K, associated with spin-density-wave instability.U doping suppresses this instability and leads to a transition to the superconducting state at temperatures up to 49 K. Magnetic measurements confirm the bulk superconductivity in this system. For the sample with a doping level of x = 0.2, the external magnetic field suppresses the onset temperature very slowly, indicating a rather high upper critical field. In addition, the Hall effect measurements show that U clearly dopes electrons into the material.
@article{arxiv.1302.5155,
title = {Superconductivity induced by U-doping in the SmFeAsO system},
author = {Bo Huang and Jijun Yang and Jun Tang and Jiali Liao and Yuanyou Yang and Ning Liu and Gang Mu and Tao Hu and Xiaoping Shen and Donglai Feng},
journal= {arXiv preprint arXiv:1302.5155},
year = {2013}
}