The coercivity of the high temperature magnets Sm(Co _balFe _0.1 Cu _0.1Zr _0.033) _6.9 alloys

The hysteresis behaviors domain structures and temperature coefficients of coercivity are investigated in Sm(Co _balFe _0.1 Cu _0.1Zr _0.033) _6.9, which is aged at 810°C and slowly cooled with a rate of 0.5°C/min, and then quenched at different temperatures. It is found that the demagnetization cures show two steps clearly as the alloys are quenched at 600°C, which means that there should have two pinnings on the domain wall, and its domain structure appears more as a zigzag shape domain, which means that there should be a small gradient of Cu distribution in the 1:5 cell boundary phase and a small domain wall pinning in the cell boundary phase. The maximum domain wall pinning should be at the interface between the 1:5 cell boundary phase and 2:17 cell phase. As the alloys are quenched at a lower temperature, the steps in the demagnetization cures disappear. At the same time, their domain structures become narrower, and show more attached domains, which means that a lower domain wall energy is in the 1:5 cell boundary phase and that the maximum domain wall pinning should be in the center of the 1:5 cell boundary phase. As the maximum domain wall pinning is at the interface between the 1:5 cell boundary phase and 2:17 cell phase, the coercivity will show an abnormal temperature dependence. While as the maximum domain wall pinning is in the center of the 1:5 cell boundary phase, the coercivity will decrease with temperature increasing. As the testing temperature rises to 500°C, the coercivities for all samples nearly come to the same values, and the maximum domain wall pinnings all should come to the interface between the 1:5 cell boundary phase and 2:17 cell phase.