Production and Characterisation of Ferromagnetic Nanoscale Metal Powders Produced by Laser Evaporation

摘要

Ferromagnetic metallic nanoscale particles were produced by laser evaporation of Co,Fe and Fe_3Al targets with vapour condensation in nitrogen,argon or air.The composition and structure of the nanoscale powders were investigated by XRD and XAS.The Fe and Fe_3Al powders condensed in nitrogen or argon consist mainly of the same phase as the targets.Small amounts of various oxides were found too.Condensation in air yields pure oxide nanopowders without metallic phases.From Co targets nanoscale particles with both fcc and hcp structure are obtained.With increasing aggregation gas pressure the mean diameter of the powders increases,leading to a higher saturation magnetisation of the coarser powders.The oxidation stability of the powders can be attributed to oxygen layers on the particles which were found to be 1-2 nm thick.