Annealing effects on superconductivity in SrFe2-xNixAs2

Abstract Superconductivity has been explored in single crystals of the Ni-doped FeAs-compound SrFe 2 - x Ni x As 2 grown by self-flux solution method. The antiferromagnetic order associated with the magnetostructural transition of the parent compound SrFe 2 As 2 is gradually suppressed with increasing Ni concentration x and bulk-phase superconductivity with full diamagnetic screening is induced near the optimal doping of x = 0.15 with a maximum transition temperature T c ∼ 9.8 K . An investigation of high-temperature annealing on as-grown samples indicate that the heat treatment can enhance T c as much as ∼ 50 % .