Yu. N. Chiang, M. O. Dzuba, O. G. Shevchenko, A. N. Vasiliev
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.
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http://arxiv.org/abs/1304.1418
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