  We used the proximity effect as a tool to achieve an ideal (barrier - free)
NS boundary for quantitative evaluation of transport phenomena that accompany
converting dissipative current into supercurrent in NS systems with
unconventional superconductors, single - crystal chalcogenide FeSe and
granulated pnictide LaO(F)FeAs. Using features (limitations) of Andreev
reflection in the NS systems with dispersion of the electron spin subbands, we
revealed direct evidence for spin - polarized nature of transport and the
absence of residual magnetization in iron - based superconductors in the normal
state: In heterocontacts with single - crystal FeSe and granular LaO(F)FeAs, we
detected a spin-dependent contribution to the efficiency of the Andreev
reflection associated with the spin accumulation at the NS boundary, and a
hysteresis of conductivity of FeSe in the ground state in low external magnetic
fields. Based on our findings, we conclude that in iron-based superconductors,
the itinerant electron magnetism is predominant, magnetism of iron atoms being
localized.
