Abstract
Experiments were carried out to investigate the magnetic properties of Sm-Fe-Co-W-Cu system nitriding compounds with TbCu7-type structure. Sm10(Fe0.95Co0.05)89.7-xW0.3Cux(x=0-0.7)alloy ribbons were prepared by the single roller rapid-quenching method, and the effects of alloy composition, and conditions of heat-treatment and nitrogenation, were examined with regards to their magnetic properties. The optimum preparation conditions of the compounds are as follows: Composition: {Sm10(Fe0.95Co0.05)89.4W0.3Cu0.3}85.1N14.9, roller velocity: 50m/s, heat treatment: 675°C×60 min in high-purity Ar gas, and nitriding condition: 420°C×15 h in high-purity N2 gas. The typical magnetic properties of the obtained compound powders are Jr=0.94T, HcJ=716.2 kA/m, HcB=519.2kA/m, (BH)max=138.1 kJ/m3(17.4 MGOe), and Tc=492°C. It was found that this sample was an exchange spring magnet from TEM photographs and recoil loops of the hysteresis curve. The value of(BH)max for the compression-molded isotropic bonded magnet prepared from the {Sm10(Fe0.95Co0.05)89.4W0.3Cu0.3}85.1N14.9 powder is 102.3 kJ/m3(12.9 MGOe), when the density of bonded magnet is 6.07 Mg/m3. The reversible temperature coefficient of Jr is α(Jr)=-0.047%/°C, the temperature coefficient of HcJ in the range from 25°C to 125°C obtained by a linear extrapolation is α(HcJ)=-0.45 %/°C.
