Enhancing magnetic stripe order in iron pnictides by RKKY exchange interactions

Recent experimental studies have revealed several unexpected properties of Mn-doped BaFe2As2. These include extension of the stripe-like magnetic (pi,0) phase to high temperatures above a critical Mn concentration only, the presence of diffusive and weakly temperature dependent magnetic (pi,pi) checkerboard scattering, and an apparent absent structural distortion from tetragonal to orthorhombic. Here, we study the effects of magnetic impurities both below and above the N'eel transition temperature within a real-space five-band model appropriate to the iron pnictides. We show how these experimental findings can be explained by a cooperative behavior of the magnetic impurities and the conduction electrons mediating the Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions between them.