Ion Beam Manipulation to Fabricate Ordered Layered Structures and Amorphous Alloys in Some highly Immiscible Binary Metal Systems

ABSTRACTWe developed a new scheme, namely ion beam manipulation, i.e. interface-assisted ion beam mixing, for fabricating amorphous alloys and artificial solid-state microstructures in metal-metal multilayers, in which the individual layer thickness is down to about 2 nm, differing significantly from the typical thickness of 5–8 nm in conventional ion beam mixing. Employing the scheme, some interesting results were obtained in three highly immiscible systems. In the Ag-W system, which has the largest positive heat of formation among the transition metal alloys, amorphous alloys were obtained, for the first time, through a two-step structural transition, i.e. the initial polycrystalline Ag and W transformed into an intermediate bcc phase, which later transformed into an amorphous state. In the Ru-Pd system, the initial polycrystalline Pd and Ru first transformed into a single crystalline FCC phase, and then turned into a well-ordered structure, which showed an apparent tendency to transform back to the FCC phase upon over-irradiation. In the Ag-Co system, an ordered layered structure was observed and identified to consist of two overlapped FCC lattices, corresponding to a new magnetic state of Co atom with an average magnetic moment measured to be 2.84 μB, which was about twice the equilibrium datum and was the largest value ever observed. We present, in this paper, a brief review concerning the scheme of ion beam manipulation in fabricating the metastable alloys, the structural evolution upon ion irradiation and the associated magnetic properties of some ordered structures obtained by the scheme.