Bulk magnetic hardening in Sm(Fe,V)12 alloys

Cast Sm-Fe-V magnets with the tetragonal crystal structure of the ThMn12 type were prepared with high coercivity through a two-step annealing at 775 degrees C and then at 825 degrees C. The annealing processing used allowed us for the first time to successfully produce a large amount of non-magnetic Sm-rich grain-boundary phase in Sm-Fe-V cast ingots. As a result, the sample with composition Sm11.1Fe75.8V13.1 showed the record-high coercivity (6.66 kOe) after annealing at 775 degrees C for 72 h and then 825 degrees C for 2 h. This coercivity, achieved without the use of powder metallurgy, has nearly doubled compared to the previously reported highest value of 3.70 kOe in a cast SmFe10V2.