Abstract
We have developed isotropic magnet powder with the composition of (Sm, Zr)(Fe, Co)zB0.1Nx (z=9-10) prepared by rapid quenching, annealing, and nitrogenation. The presence of both zirconium and cobalt make it possible to realize a nearly single phase of the TbCu7 structure with a c/a ratio as high as 0.87. These powders show a high saturation magnetization of 1.6-1.7 T. A small addition of boron is effective for forming the amorphous phase in the rapidly quenched alloys and for obtaining uniform and fine grains of the ThCu7 phase after annealing. The combination of the high saturation magnetization and the fine grains leads to high Br and high (BH)max. The magnetic properties of these powders are as follows: Br=1.00-1.07T, HcJ=640-880kA/m, (BH)max=160-180kJ/m3. Isotropic bonded magnets fabricated using such powder show highest (BH)max of 120kJ/m3. These bonded magnets also show good thermal stability and good oxidation resistance.
