Crystallization and magnetic properties of ThMn12-type Sm-Fe-Co-Ti-Si based magnetic materials

Si-doped Fe-rich compounds, i.e., Sm(Fe0.8Co0.2)11Ti + Six (x = 0, 0.5, and 1.0), with ThMn12-type structure in forms of ribbons and bulks were fabricated using melt-spinning process and high pressure pressing and heat treatment processes. Physical and magnetic properties of the ribbons and bulks were analyzed to investigate Si doping effects on the Sm(Fe0.8Co0.2)11Ti. The Si-free ribbons were found to be amorphous, while the small amount of Si doping resulted in dramatic crystallization of the ThMn12 phase. Coercivity of the ribbons increased with the increasing Si content from 43 to 3140 Oe, while the magnetization decreased from 146 to 78 emu/g. It was observed that the Si-free ribbons consisted of nano-sized grains in the matrix of an amorphous phase. On the other hand, the Si-doped ribbons exhibited submicron-sized grains with high crystallinity. The crystallized phases of the heat-treated bulks varied with the Si concentrations; the main phase was the ThMn12 phase in all samples, but concentrations of soft magnetic α-Fe phase decreased with the increasing Si concentration, and corresponding saturation magnetizations of the bulks also decreased.