Superconductivity and magnetic properties in SmFe_1−xCo_xAsO (x=0 to 1)

Key Laboratory of Applied Superconductivity, Institute of Electrical Engineering, Chinese Academy of Sciences P. O. Box 2703, Beijing 100190, China

^a ywma@mail.iee.ac.cn

Received: 20 July 2011
Accepted: 18 August 2011

Abstract

In this paper the effects of replacing Fe with Co in SmFe_1-xCo_xAsO (x=0 to 1) are reported. X-ray diffraction patterns indicate that all the samples have formed the ZrCuSiAs-type structure with a space group P4/nmm and a full solid solution forms between SmFeAsO and SmCoAsO. It is found that the antiferromagnetic spin-density-wave (SDW) order in the parent compounds is rapidly suppressed by Co-doping, and superconductivity emerges as 0.05 ≤ x ≤ 0.175. A phase diagram is derived based on the resistivity measurements and a dome-like T_c-vs.-x curve is established. Furthermore, it was shown that the metallic character increases with the addition of more Co. Meanwhile we found that the two magnetic phase transitions in SmCoAsO are suppressed as Co is replaced by Fe. Our work demonstrates that the solid solution has been established in the SmFeAsO-SmCoAsO system. The systemic study in the SmFe_1-xCo_xAsO system would add more ingredients to the underlying physics of this material.