The hexagonal ferrite W=BaFe2+2Fe3+16O27 has a saturation magnetization about 10% higher than the widely used permanent-magnet material M=BaFe3+12O19 and the anisotropy field is about equal. This opens up the possibility of using W as a permanent-magnet material with a higher remanence Br and energy product BHm. This paper describes the sintering of W having a slight deviation from the stoichiometric composition and containing a trace of SiO2 at, e.g., 1220 °C in a reducing atmosphere to 92–95% of the x-ray density and containing well-oriented grains of 2–8 μm. Samples with coercive forces Hc=1.5–2.1, Br=4.4–4.7, and BHm=3.7–4.3 (B in kG, H in kOe) were obtained, which may be compared with Hc=2.1, Br=4.0, and BHm=3.4 found from our own measurements on high-quality commercial M. We found surprisingly that the pickup of a trace iron during grinding increases the sintering density considerably, and this is therefore essential for the preparation of useful material.
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