Magnetic properties of TbCu7-type Sm-Fe-Co-Cr-Y system nitrided compounds

Experiments were carried out to investigate the effects of composition, heat-treatment and nitrogenation conditions on the magnetic properties of Sm-Fe-Co-Cr-Y-N compounds with the TbCu7-type structure. The optimum preparation conditions of the compounds were as follows: composition: {Sm 10(Fe0.9Co0.1)89.4Cr 0.3Y0.3}86.6N13.4 roller velocity: 50 m/s, heat treatment: 680°C for 60 min in high-purity Ar gas, and nitrogenation condition: 420°C for 10 h in highpurity N2 gas. Typical magnetic properties of the obtained compound powders were as follows: Jr=0.98 T, Hcj= 765.1 kA/m, HcB = 545.4 kA/m, (BH)max = 138.5 kJ/m3 (17.4 MGOe), and T c=523°C. It was found that this sample was an exchange spring magnet from recoil loops of the hysteresis curve, X-ray diffraction patterns and σ-T (Magnetization-Temperature) curve. The value of (BH)max for a compression-molded isotropic bonded magnet prepared by using {Sm 10(Fe0.9Co0.1)89.4Cr 0.3Y0.3}86.6N13.4 powder was 96.2kJ/m3 (12.1 MGOe), when the density of bonded magnet was 6.05 Mg/m 3. And the average reversible temperature coefficient of J r was α(Jr)ave=- 0.05 %/°C, the temperature coefficient of Hcj in the range from 25°C to 125°C obtained by a linear extrapolation was α (Hcj)=- 0.40 %/°C.