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

抄録

  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(Fe_0.9Co_0.1)_88.7Ti_0.3Zr_0.5 Y_0.5}_85.6N_14.4, 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: J_r=0.98 T, H_cJ=751.5kA/m, H_cB=544.7 kA/m, (BH)_max=147.0 kJ/m³ (18.5 MGOe), and T_c=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(Fe_0.9Co_0.1)_88.7Ti_0.3Zr_0.5Y_0.5}_85.6N_14.4 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 J_r was α(J_r)_ave. =-0.05%/°C, and the temperature coefficient of H_cJ in a range from 25 to 125°C obtained by linear extrapolation was α(H_cJ) =-0.46 %/°C.