Measurements of interdiffusivities in Cu/NiFe ternary alloy thin films

Interdiffusivities have been measured in Cu/NiFe ternary alloys containing 53at.% Cu, 40 at.% Ni and 7 at.% Fe. Isothermal anneals were performed at temperatures: 320, 345 and 400°C using thin films containing composition modulations (1.6-4.98 nm) produced by the vapor-phase growth technique. Spinodal decomposition in these films was observed in the X-ray diffraction pattern as indicated by the growth of satellite intensities at 320°C. The diffusivities at each temperature were determined from the growth or decay rate of the composition modulation. A plot of the interdiffusion coefficient D ̃_B, versus the dispersion relation B² demonstrated anomalous behavior at certain wavelengths at which an enhanced elastic modulus effect is observed. The critical spinodal temperature was estimated and first three gradient energy coefficients were calculated using a nonlinear regression fit to the D_B vs B² curve.