| dc.description |
The formation, crystal structure and magnetic properties of Sm<sub>2</sub>Fe<sub>17−x</sub>Co<sub>x</sub>C<sub>y</sub> were studied. The substitution of Co for Fe helps to stabilize the rhombohedral Th<sub>2</sub>Zn<sub>17</sub>-type structure (2:17) and eliminate α-Fe formation for carbon concentrations y <sup>≤</sup> 1.5. From the mixing enthalpy calculations based on Miedemas semi-empirical model and Wigner–Seitz cell analysis, it is found that the role of Co in stabilizing the 2:17 structure is related to its strong preference for the 18h site, which has a maximum number of rare-earth near neighbours in the structure. With increasing Co content, x, the lattice constants decrease while the Curie temperature rapidly increases. The typical compound Sm<sub>2</sub>Fe<sub>12</sub>Co<sub>5</sub>C<sub>1.25</sub> has a room temperature saturation magnetization μ<sub>0</sub>M<sub>s</sub> 1.36 T, a magnetic anisotropy field μ<sub>0</sub>H<sub>k</sub> 7.1 T, a Curie temperature T<sub>C</sub> 874 K and a possible maximum operating temperature T<sub>m</sub> higher than 473 K. |
