Enhanced magnetic hyperfine field of the surfaces of Fe nanocrystals

Abstract Fine oxide-free metallic Fe particles with an average crystal size of 6 and 10 nm were prepared by the inert-gas condensation technique. The particles were suspended in silicon oil or paraffin to prevent oxidation. The magnetic surface properties of these particles were studied by Mossbauer spectroscopy. Spectra taken at lower temperatures showed an asymmetric broadening of the outer lines. A fairly good fit of the spectra was obtained by assuming two components corresponding to the surfaces with a thickness of 2 atomic layers and the interior of the particles. For the surface component a 5% increase of the hyperfine field was found.