Experiments were carried out to investigate the magnetic properties of Sm-Fe-Co-W system nitriding compounds with TbCu
7-type structure. Sm
y(Fe
0.95Co
0.05)
100-x-yW
x(x=0-1.0, y=8-11) 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: {Sm
10(Fe
0.95Co
0.05)
89.7W
0.3}
85.0N
15.0, roller velocity: 50 m/s, heat treatment: 675°C×60 min in high-purity Ar gas, and nitriding condition: 400°C×15 h in high-purity N
2 gas. Typical magnetic properties of the obtained compound powders are H
cJ=765.7 kA/m (9.62 kOe), J
r=0.93 T (96.40 emu/g), (BH)
max=134.5 kJ/m
3 (16.9 MGOe), and T
c=480°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: {Sm
10(Fe
0.95Co
0.05)
89.7W
0.3}
85.0N
15.0 powder is 95.0 kJ/m
3 (12.0 MGOe), when the density of bonded magnet is 6.1 Mg/m
3. And the reversible temperature coefficient of J
r is α(J
r)=-0.071 %/°C, the temperature coefficient of H
cJ in the range from 25°C to 125°C obtained by a linear extrapolation is α(H
cJ)=-0.42%/°C.
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