Phase composition and magnetic properties of post-annealed asymmetric Pt/Fe/Pt/Au/Fe thin films

•Evolution of phase transitions in Pt/Fe/Pt/Au/Fe and Pt/Fe stacks upon annealing.•Reduction of annealing temperature and time needed for chemical L10 ordering onset.•Enhancement of coercivity via Au layer introduction.•Coexistence of soft and hard magnetic phases after annealing.•Pathway to create exchange graded magnetic nanomaterials. Intermetallic compound formation realized via thermally-induced diffusion intermixing of layered stacks is a prospective route for the formation of thin films with properties promising for practical applications. This can be further promoted by the addition of third elements which could provide acceleration of diffusion and ordering processes during post-annealing. In the present study, we have investigated the structural and magnetic properties of post-annealed Pt/Fe/Pt/Au/Fe thin films which contain an additional asymmetric Au layer and compare the results with Fe/Pt bilayers. It was shown that the introduction of an Au layer reduces both the onset temperature and the annealing time for promoting the formation the hard magnetic L10-FePt phase while the remaining layer stack develops a magnetically soft Pt-rich disordered FePt solid solution. Thus, different diffusion pathways present in asymmetric layer stacks can provide an intriguing root for thin film materials synthesis of exchange coupled soft and hard magnetic phases which could be of particular interest for the creation of graded magnetic nanomaterials.