Interdiffusion in nanometric Fe/Ni multilayer films

[Fe (3.1 nm)/Ni (3.3 nm)]₂₀ multilayer films were prepared by DC magnetron sputtering onto oxidized Si(100) substrates. The Fe and Ni layers were shown to both be face-centered cubic by x-ray diffraction. Interdiffusion of the Fe and Ni layers in the temperature range of 300–430 °C was studied by x-ray reflectivity. From the decay of the integral intensity of the superlattice peak, the activation energy and the pre-exponential term for the effective interdiffusion coefficient were determined as to 1.06 ± 0.07 eV and 5 × 10⁻¹⁰ cm²/s, respectively. The relevance of the measured interdiffusion coefficient to the laboratory timescale synthesis of L1₀ ordered FeNi as a rare-earth free permanent magnet is discussed.