Srフェライトの粒子形態と磁気特性に及ぼす組成の影響

概要

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Samples of SrO⋅nFe2O3 with 5.4≤n≤6.4 were prepared by calcination at 1275°C in air for I h of mixtures of SrCO3 and a-Fe203. Each calcined sample was pulverized in the presence of extremely slight amounts of CaCO3 and SiO2 as additives, compacted under the pressure 350 kg/cm2 in a magnetic field 12kG, and sintered at 1220±10°C in air for 1 h. Composition dependences of the particle shape and the magnetic properties of the calcined samples and of the sintered magnets containing 0.75 wt% CaO and 0.6 wt%SiO2 were investigated. The particle shape of the calcined sample was changed drastically by the composition. The saturation magnetization (σs) decreased, while the intrinsic coercivity (iHc) increased with decreasing SrO content in the calcined sample. On the other hand, the residual magnetization (Br) increased and iHc decreased with decreasing SrO content in the sintered magnet, depending on the grain shape and size in the magnet. The high performance magnet could be prepared with n??5.9 under these experimental conditions.
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