High moment epitaxial Fe-N thin films

High moment epitaxial Fe-N films were produced using reactive sputtering in an ultra clean sputtering system with in-situ RHEED, and the effects of ni trogen concentration and annealing on magnetic and structural properties we re investigated. A sulfur-passivated GaAs substrate was annealed at 450 deg reesC to get a good RHEED pattern. A 1 mn thick Fe seed layer was then depo sited to promote epitaxial growth of a 20 mu thick Ag(100) buffer layer. Fe -N films were grown on these Ag(100) buffer layers. Nitrogen partial pressu re and annealing temperature was varied to obtain epitaxial high moment fil ms. Epitaxial GaAs(001)/1 mn Fe/20 mn Ag(001)/40 mn Fe-N(001)/Ru 10 nm film s with low nitrogen concentration exhibited an alpha ' -FeN single phase wi th a magnetization of about 18 kG. Films with high nitrogen concentration e xhibited a mixture of alpha ' -FeN and gamma ' -Fe4N phases, resulting in l ow magnetization. Post-annealing of films with low nitrogen concentration i ncreased the magnetization up to 20 kG, but the post-annealing of films wit h high nitrogen concentration increased the amount of the gamma ' -Fe4N pha ses, resulting in lower magnetization. For films with low nitrogen concentr ation, sharp RHEED streaks are observed and this is an indication of well-o rdered smooth epitaxial films. For films with high nitrogen concentration R HEED streaks are broadened and the background increases which is indicative of an increasing amount of disorder and roughness or possibly a multiphase film. Rms surface roughness of the films was in the range of 0.2-0.6 mn.