Divergency of SDW and structure transition in Fe1-xNixSe0.82 superconductors

The effect of the Ni-substitution on the superconductivity of alpha-FeSe0.82 system has been investigated. It is found that the superconductivity of alpha-FeSe0.82 can be quickly suppressed when a small quantity of Fe is Substituted by Ni element. The resistivity and moment of the sample at normal state increase with increasing Ni-substitution content. Moreover, it is found that the Ni-substitution does not change the structure transition temperature, but increases the spin density wave (SDW) order temperature. It is suggested that the quick suppression of superconductivity of alpha-FeSe0.82 caused by the Ni-substitution is related to the increase of SDW order temperature. Therefore, Fe atom plays a key role for the appearance of the superconductivity in FeSe system. (C) 2009 Elsevier B.V. All rights reserved.