TbCu7型構造Sm-Fe-Co-Ti-Zr-Y 系窒化化合物磁石の磁気特性

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Experiments were carried out to investigate the effects of composition, heat-treatment, and nitrogenation conditions on the magnetic properties of Sm-Fe-Co-Ti-Zr-Y-N compounds with a TbCu7-type structure. The optimum preparation conditions for the compounds were: composition: {Sm10(Fe0.9Co0.1)88.7Ti0.3Zr0.5 Y0.5}85.6N14.4, roller velocity: 50m/s, heat treatment: 660°C for 60min in high-purity Ar gas, and nitrogenation conditions: 420°C for 10h in high-purity N2 gas. Typical magnetic properties of the obtained compound powders were: Jr=0.98 T, HcJ=751.5kA/m, HcB=544.7 kA/m, (BH)max=147.0 kJ/m3 (18.5 MGOe), and Tc=510°C. We found that a sample made from these compound powders was an exchange spring magnet from the recoil loops of the hysteresis curves, X-ray diffraction patterns, and σ-T (Magnetization-Temperature) curves. The value of (BH)max for an isotropic compression-molding bonded magnet prepared by using {Sm10(Fe0.9Co0.1)88.7Ti0.3Zr0.5Y0.5}85.6N14.4 powder was 92.7 kJ/m3 (11.7 MGOe), when the density of the bonded magnet was 6.08 Mg/m3. The average reversible temperature coefficient of Jr was α(Jr)ave. =-0.05%/°C, and the temperature coefficient of HcJ in a range from 25 to 125°C obtained by linear extrapolation was α(HcJ) =-0.46 %/°C.