Driving the system into the normal state is certainly the traditional way that magnetism vs. superconductivity is understood. But, of more interest these days is the separate possibility that magnetic fluctuations actually cause superconductivity in materials such as iron pnictides, with the separate question of whether the underlying magnetism is itinerant or local-moment. See for example the review of Stewart (Rev. Mod. Phys. 83, 1529) for some discussion; as far as I know it is still not clear whether the magnetism is itinerant or not. However the "superconducting dome" and nearness to a magnetic phase transition with T near zero seems to indicate that magnetism plays a major role in driving the superconducting state in such systems (and cuprates, UGe2, etc.).

So it seems that problem here is still under debate. For our iron-122 compounds it is clearly declared by G.R.Stewart in Rev.Mod.Phys.83.1589 (page 1607).

(Prof. Ross, 

I am grateful for your guidance. Regards)