Structural relaxation within the grain boundaries of nanocrystalline Ni3Fe

Results are reported from small-angle neutron scattering (SANS) and Mossbau er spectrometry measurements on four Ni3Fe materials: nanocrystalline mater ial prepared by mechanical attrition, nanocrystalline material after an exp osure to 4K, nanocrystalline material after a heat treatment of 100 degrees C for 10 days, and a control sample composed of large crystals. Scattering from the nanocrystalline materials after thermal treatments showed changes in the intensity and the slope of both the nuclear and the magnetic scatte ring profiles of the SANS measurements. The Mossbauer spectra from the nano crystalline samples showed changes in the hyperfine fields associated with grain-boundary atoms. The changes induced by cryogenic exposure and anneali ng at 100 degrees C were somewhat different but were consistent with a shar per density gradient between the crystalline region and the grain-boundary region. Some grain-boundary atoms in mechanically attrited Ni3Fe are in ene rgetically unfavourable positions, and move into new positions during these low-temperature treatments.