Inter-element miscibility driven stabilization of ordered pseudo-binary alloy.

An infinite number of crystal structures in a multicomponent alloy with a specific atomic ratio can be devised, although only thermodynamically-stable phases can be formed. Here, we experimentally show the first example of a layer-structured pseudo-binary alloy, theoretically called Z3-FePd. This Z3 structure is achieved by adding a small amount of In, which is immiscible with Fe but miscible with Pd and consists of an alternate L1 (CuAu-type)-PdFePd trilayer and Pd-In ordered alloy monolayer along the c axis. First-principles calculations strongly support that the specific inter-element miscibility of In atoms stabilizes the thermodynamically-unstable Z3-FePd phase without significantly changing the original density of states of the Z3-FePd phase. Our results demonstrate that the specific inter-element miscibility can switch stable structures and manipulate the material nature with a slight composition change.