Magnetic and structural transitions in layered iron arsenide systems:: AFe2As2 versus RFeAsO

Resistivity, specific-heat, and magnetic-susceptibility measurements performed on SrFe2As2 samples evidence a behavior very similar to that observed in LaFeAsO and BaFe2As2, with the difference being that the formation of the spin-density wave and the lattice deformation occur in a pronounced first-order transition at T-0=205 K. Comparing further data evidences that the Fe magnetism is stronger in SrFe2As2 and in EuFe2As2 than in the other layered FeAs systems investigated up to now. Full potential local-density approximation band-structure calculations confirm the large similarity between the compounds, especially for the relevant low energy Fe 3d states. The relation between structural details and magnetic order is analyzed.