Structural configuration and magnetic effects in as-milled and annealed nanocrystalline iron

Mechanical spectroscopy, room temperature Mössbauer spectroscopy and magnetisation measurements have been employed to get insight into the structural relaxation process of the grain boundaries in 10 nm-grain sized iron powders produced by ball milling In particular, by performing the Mössbauer analysis on milled powders previously subjected to proper thermal treatments in the 570-670 K range, the structural evolution of the grain boundaries has been followed through the changes in the hyperfine magnetic field distribution associated to the interfacial region. The results are consistent with a decrease of the magnetic moment of the atoms at the interface, following the relaxation process.