An AuFe ordered alloy has been synthesized artificially by depositing alternately monatomic layers of Au and Fe. The thermal stability and interdiffusion have been investigated by X-ray diffraction measurements. X-ray diffraction from the AuFe thin films shows definite superlattice lines corresponding to the L10-type ordered structure, although neither intermediate phase nor intermetallic compound is known for the Au-Fe binary equilibrium phase diagram. At 473 K, L10-type ordered structure is maintained until 10 ks and then, the structure changes to metastable disordered structure. The interdiffusivity is determined from the decay rate of the superlattice peak intensity. The interdiffusivity at 473 K is evaluated as (1.7±0.1) × 10-25 m2 s-1 for L10-type ordered phase, which is in good agreement with that extrapolated from the bulk-interdiffusivity at high temperatures. The diffusion is interpreted as an atomic mixing process for deteriorating the L10-type ordered structure.
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