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Iron powders have been produced by the reduction of ferrous ion with borohydride and stabilized by a chromating procedure. The saturation moments is 140 to 160 emu/g. The coercivity can be controlled between 375 and 1150 Oe. Remanence is 0.45 to 0.5 for unoriented powders. The powders are fibers up to 3 μm long and 1000 Å wide consisting of agglomerated spherical crystallites 300 to 450 Å in diameter. Chemical analyses show that typical powders contain about 82–85% Fe, 2–3% B, 3% Cr, 5–6% O, and 0.2% H. The moment indicates that only 70% is metallic iron. Measurements up to 100 KG show no superparamagnetic fraction. Fe(OH)2 and FeOOH were identified by electron diffraction in some but not all the preparations. Chromating may result in the removal of some non-magnetic by-products. Following the chromating treatment, water is removed with methanol. Solvent-wet powder containing less than 0.1% water can be stored at least 3 months without loss in moment. Cured films of dispersions in a typical epoxy-type binder lose moment in an accelerated atmosphere test containing SO2 and NO2 at a rate indicating a lifetime of 10 years in a worst-case indoor ambient.

Permalloy films (83 wt% Ni-17 wt% Fe) epitaxially grown on (100) NaCl were examined in the electron microscope before and after beam annealing. An ultra-high vacuum system with an ultimate vacuum of 10−10 Torr and a vacuum system with an ultimate vacuum of 10−6 Torr were used for the evaporation. Films at 10−5 Torr were prepared in both systems to rule out the influence of the vacuum system on the films. Evaporation rates were adjusted to either 30 Å/sec or 14 Å/min. Electron micrographs and electron diffraction patterns showed that the films ranged from polycrystalline for films evaporated at 30 Å/sec and 10−5 Torr to single crystalline with grains of several millimeters diameter for films evaporated at 30 Å/sec and 10−9 Torr. The crystallographic misorientation varied widely in films which were partially single crystalline and amounted to only a few degrees over areas up to ⅛-in. diameter for films which exhibited perfect single-crystal electron diffraction patterns.

The magnetic characteristics of cylindrical electroplated films are considered. Pertinent previous work is reviewed and new data are presented which elucidate the following items: (a) Preparation. The influence of surface roughness is emphasized, and important recent work on surface topology is reviewed. (b) Magnetic Characterization. The use of susceptibility measurements to determine the anisotropy and the ripple amplitude are discussed. When the ripple amplitude is large, previous calculations of the susceptibility based on the linear ripple theory do not apply. Nevertheless, it is possible to use the susceptibility to characterize the anisotropy and dispersion if the susceptibility is described in terms of a phenomenological ripple field picture. (c) Domain Wall Creeping. The possible causes of creep in thick films are considered. From the thickness dependence of the creep threshold, it does not appear that the Olson-Torok model is adequate. Data on the creep velocity are presented. Finally, a model for creep is described which hinges on the distribution of wall motion fields along the wall. (d) Thermal Stabilization. It is shown that by annealing at elevated temperatures, adequate thermal stabilization of plated films can be achieved.

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