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Spin-dependent conductivity of iron-based superconductors in a magnetic field

We report the results of a study of magnetic field features of electron transport in heterojunctions with NS boundary inside iron-based superconductors, represented by a binary phase of $α$ - FeSe and oxyarsenide pnictide LaO(F)FeAs. We used the ability of self magnetic field of the transport current to partially destroy superconductivity, no matter how low the field may be, in the NS interface area, where, due to the proximity effect, the superconducting order parameter, $Δ$, disperses from 1 to 0 within the scale of the Ginzburg-Landau coherence length. The following features of transport were found:(i) at $T<T_{c}$, magnetoresistance in systems with different superconductors has different sign;(ii) sign and magnitude of the magnetoresistance depend on the magnitude of current and temperature, and (iii) in all operating modes where the contribution from Andreev reflection is suppressed ($(T + eV) \gtrsim Δ$),the hysteresis of the magnetoresistance is present. Based on the results of the experiment and analysis it has been concluded that there is along-range magnetic order in th eground normal state of the iron-based superconductors studied, in the presence of itinerant magnetism of conduction electrons which determines the possibility of anisotropic spin-dependent exchange interaction with the local magnetic moments of the ions.