Non-equilibrium phases in the Fe-Rh system studied by ion beam mixing and ab initio calculation

In the Fe-Rh system, the Fe_100 − xRh_x (x = 40, 50, 65, 70, and 90) multilayered films were prepared and then subjected to ion beam mixing using 200 keV Xe ions. Upon ion beam mixing, amorphous alloy was obtained in the Fe₇₀Rh₃₀ sample, in which an interesting phase transition path was observed as Fe + Rh → fcc → fcc + a →? fcc + bcc → fcc. In addition, a new metastable crystalline fcc phase was observed in the Fe₅₀Rh₅₀ sample together with the solid solutions, and the lattice constants of the ion mixed phases were consistent with those from ab initio calculations. Possible mechanisms for the formation of both amorphous and metastable crystalline phases are discussed in terms of the atomic collision theory.