The mechanism of anisotropic exchange interaction in superconducting iron arsenides

Using a combination of linear response theory and constrained orbital hybridization approach, we study the mechanism of magnetic exchange interaction of iron-based superconductor. We reproduce the observed highly anisotropic exchange interaction, and our constrained orbital calculation unambiguously identifies that the anisotropic feature of exchange interaction is not sensitive to the unequal dxz/dyz orbital population. -- Highlights: ► We unambiguously identify that the magnetic exchange process happens in the FeAs layer. ► The highly anisotropic feature of exchange interaction is not related to the orbital polarization. ► The magnetism is at least partially itinerant, which results in the anisotropic exchange interaction.