Ordered Pt3–Co Alloy Studied in the Field-Ion Microscope

Abstract
Atomically resolved field‐ion microscope images of the {111} planes of ordered Pt3–Co confirm unambiguously our hypothesis of the invisibility of the Co atom species in Pt–Co alloys. From the known lattice structure, L12, the composition of {110} and {100} planes of ordered Pt3–Co are expected to alternate in subsequent layers between pure Pt layers and equiatomic Pt and Co layers. This is confirmed by direct observation during controlled layer‐by‐layer field evaporation. Antiphase domains show up clearly only when the domain boundary passes through a {110} or {100} plane, but tracing the boundary through the matrix is difficult. No sharp boundary between the ordered and the disordered phase has been observed in the partially ordered state of the alloy.