Structural and magnetic properties of rhombohedral Sm/sub 2/(Co,Fe,Cr)/sub 17/B/sub x/ and Sm/sub 2/(Co,Fe,Mn)/sub 17/B/sub x/ compounds

Single-phase rhombohedral Sm/sub 2/(Co/sub bal/Fe/sub 0.2/M/sub y/)/sub 17/B/sub x/ with M = Cr or Mn substituting for Co have been prepared and the influence of transition metals on crystal structure, anisotropy field, and Curie temperature is examined. Sm/sub 2/Co/sub 17/ as-cast bulk sample has the 2 : 17 hexagonal structure (type Th/sub 2/Ni/sub 17/), while boron addition stabilizes the 2 : 17 rhombohedral structure (type Th/sub 2/Zn/sub 17/). Anisotropy field for Cr-doped as-cast sample is 74 kOe. Secondary phases of fcc-Co or Fe-Co are observed in some cases. A Cr-doped sample with y = 0.1 after annealing at 1190(degree)C for 26 h is single phase. Curie temperatures of as-cast samples vary from ~849(degree)C to ~687(degree)C depending on the composition. Mechanical alloying and melt spinning were used to develop coercivity. As-spun ribbons at 53 m/s with Cr present a nanocomposite structure with H/sub c/ = 5.2 kOe. Samples with Mn have a coercive field close to 0.4 kOe. Scanning electron microscopy studies show different microstructure for Mn and Cr substituted ribbon samples.