Effect of a carbon additive on the TbCu7-type melt-spun Sm(Co, M)7 (M=Ti, Zr, Hf, V and Ge) ribbons

The effect of a carbon additive on the microstructure and the magnetic properties of melt-spun SmCo7−xMxCy (M=Ti, Zr, Hf, V and Ge; x = 0–0.3 and y = 0–0.1) ribbons was studied. Based on the XRD and the TEM analyses, a pure 1:7 phase could be formed for the C-containing ribbons with M= Ti and Ge. However, carbide phases, i.e., Sm2C3 for M=Zr and Hf, and SmCoC2 for M=V, respectively, were found. Nevertheless, a slight C addition may effectively refine the microstructure and improve both the intrinsic coercvity and the magnetic energy product in all the studied ribbons. Among them, the SmCo6.9V0.1C0.1 ribbons with σr = 58.7 emu/g, iHc = 13.5 kOe and (BH)max = 9.3 MGOe, and the SmCo6.9Hf0.1C0.1 ribbons with σr = 61.6 emu/g, iHc = 11.8 kOe and (BH)max = 10.3 MGOe are most suitable for the bonded magnet applications.