STRUCTURE AND MAGNETIC-PROPERTIES OF SPUTTERED THIN-FILMS OF FE0.79GE0.21

Films of Fe0.79Ge0.21 with thicknesses of 300 nm were synthesized by i on beam sputtering, and were annealed at temperatures from 200 to 550- degrees-C. The materials were characterized by x-ray diffractometry, M ossbauer spectrometry, vibrating sample magnetometry, ferromagnetic re sonance spectrometry, and electrical resistivity measurements. The as- prepared materials comprised chemically disordered bcc crystallites of sizes less than 20 nm, and were found to have a distribution of inter nal strains. Upon annealing at temperatures of 250-degrees-C and below , there occurred strain relaxation, some evolution of short range chem ical order, and an improvement in soft magnetic properties. The coerci ve field was a minimum for the sample annealed at 250-degrees-C. Cryst allite growth occurred at higher annealing temperatures, accompanied b y a transition in several measured parameters from those of ultrafine grained materials to those typical of polycrystalline materials. This trend can be explained with the random anisotropy model. Mossbauer and magnetization measurements indicated that the Ge atoms behave as magn etic holes. The Fe-57 hyperfine magnetic field distribution, and its c hange during chemical ordering, can be calculated approximately with a model of magnetic response. The large local isomer shifts at Fe-57 at oms near Ge atoms suggest that a local depletion of 4s conduction elec tron density should be incorporated into the model.