Sm3(Fe,Co,Mo)29 compounds:: promising materials for permanent magnets

The outstanding hard-magnetic properties are reported of Sm3Fe28.1-xCoxMo0.9 compounds with x=12, 14, 16. In this alloy system, only a small amount of Mo is needed to stabilize the 3:29 structure so that the magnetic properties are not seriously affected by the presence of this nonmagnetic element. Substitution of Co for Fe leads to a significant increase of the magnetic anisotropy, and for x greater than or equal to 14 the easy magnetization direction changes from easy plane to the easy axis. In this alloy system, the compound Sm3Fe12.1Co16Mo0.9 is a very promising candidate for permanent magnet applications. Its room temperature saturation magnetization (mu(0)M(s)=1.5T) and anisotropy field (B-an=6.5 T) are comparable to the values for Nd2Fe14B (mu(0)M(s)=1.6 T and B-an=7 T). However, the Curie temperature of Sm3Fe12.1Co16Mo0.9 is 1020 K, which is appreciably higher than that for Nd2Fe14B (T-C=588 K).