The geometries, electronic structures and magnetic moments of the Fe n Cr (n=1–12) clusters have been systematically investigated using all-electron density functional theory. For the lowest-energy structures of Fe n Cr, the single Cr atom sits on the surface for all clusters up to n=10. For n=11 and n=12 the Cr atom falls into the interior site. For Fe n Cr (n=1–8,10–12), the local moment of the Fe atoms is found to align antiferromagnetically with respect to that of the Cr atom, while for Fe 9 Cr, the local moments of the Fe atoms are ferromagnetic with respect to that of the Cr atom.