Iron self-diffusion in FeZr/⁵⁷FeZr multilayers measured by neutron reflectometry: Effect of applied compressive stress

Iron self-diffusion in nano-composite FeZr alloy has been investigated using neutron reflectometry technique as a function of applied compressive stress. A composite target of (Fe+Zr) and (57Fe+Zr) was alternatively sputtered to deposit chemically homogeneous multilayer (CHM) structure, [Fe75Zr25/57Fe75Zr25]10. The multilayers were deposited on to a bent Si wafer using a 3-point bending device. Post-deposition, the bending of the substrate was released which results in an applied compressive stress on to the multilayer. In the as-deposited state, the alloy multilayer forms an amorphous phase, which crystallizes into a nano-composite phase when heated at 373 K. Bragg peaks due to isotopic contrast were observed from CHM, when measured by neutron reflectivity, while x-ray reflectivity showed a pattern corresponding to a single layer. Self-diffusion of iron was measured with the decay of the intensities at the Bragg peaks in the neutron reflectivity pattern after thermal annealing at different temperatures. It was found that the self-diffusion of iron slows down with an increase in the strength of applied compressive stress.