Self-Diffusion in 57Fe/natFe Multilayers by In Situ Neutron Reflectometry

Abstract

Time-of-flight in situ neutron reflectometry (i-NR) on Si/[57Fe(x nm)/natFe(x nm)]4/Pt with x = 4 and 8 nm multilayers during consecutive heat treatments at 423, 448, 473 and 498 K reveal an unexpected rearrangement of free volumes and an interface smoothening in the isotopic Fe multilayer below 473 K, before the regime of regular Bragg intensity decay starts. The bilayer period dependence of the diffusivities at around 500 K, however, does not follow predictions of Harrison’s theory for the C-type regime representing grain boundary diffusion.