Short-range order and magnetic properties of nanocrystalline FexCu1-x

Nanocrystalline Fe-Cu powders with an average particle size of 800 Angstrom were prepared by evaporating Fe and Cu wires in a high-voltage are produce d in a high-frequency inductor in vacuum, followed by condensation in a low -pressure inert-gas flow. The Fe0.15Cu0.85 and Fe0.19Cu0.81 alloys were cha racterized by x-ray diffraction and Mossbauer measurements. The iron atoms were shown to be in three different magnetic states: (1)the ordered magneti c phase alpha-Fe, (2) a paramagnetic phase formed by separate iron atoms em bedded in the copper matrix, and (3) a paramagnetic phase formed by iron di mers or small clusters in the copper matrix. The experimental isomer shift data for phase (2) were compared with first-principles Korringi-Kohn-Rostoc ker calculations in the coherent-potential approximation for FexCu1-x subst itutional alloys.