Impurity phases in Sm(CoFeCuZr)z magnets: The role of Zr

Isotropic magnets were produced from cast alloys with composition Sm(CobalFe0.2Cu0.1Zrx)8 (x = 0, 0.02, 0.04, 0.06 and 0.08). They were homogenized for 4 h at 1175 °C and then quenched into water. An isothermal treatment for 7 h at 820 °C was followed by a slow cooling (−1 °C/min) to 400 °C. For the Zr-free material (x = 0), we find μ0iHc = 0.17 T, while, for x = 0.02, the intrinsic coercivity has climbed to μ0iHc > 2 T and thereafter decreases with increasing Zr. Three main impurity phases were found in alloys with elevated Zr, and these phases can be identified with phases reported in the literature. The presence of the other phases could be related to the drop in iHc for the high Zr alloys.