Ab initio investigation of FeAs/GaAs heterostructures for potential spintronic and superconducting applications

Ultrathin FeAs is of interest both as the active component in the recently identified pnictide superconductors and in spintronic applications at the interface between ferromagnetic Fe and semiconducting GaAs. Here we use first-principles density-functional theory to investigate the properties of FeAs/GaAs heterostructures. We find that the Fermi surface is modified from that characteristic of the pnictide superconductors by interactions between the FeAs layer and the As atoms in the GaAs layers. Regardless of the number of FeAs layers, the Fe to As ratio, or the strain state, the lowest-energy magnetic ordering is always antiferromagnetic, offering an explanation for the failure of spin injection across Fe/GaAs interfaces. However, such antiferromagnetic layers could be incorporated into heterostructures as an exchange-bias layer.