Tuning intrinsic magnetic properties of Sm(Fe1− x Co x )10V2 compounds with ThMn12-type structure

The development of high-performance ThMn12-type SmFe12 based permanent magnets is limited by an intrinsic trade-off between the thermodynamic stability of the 1:12 phase and its magnetic performance. While stabilizing elements such as vanadium are essential for phase formation, they often dilute the magnetic properties. In this work, we demonstrate a strategy to overcome this limitation by systematically investigating the dual role of cobalt (Co) substitution in V-stabilized Sm(Fe1-xCox)10V2 compounds. It is revealed that a moderate Co content (x ≤ 0.2) not only enhances the intrinsic magnetic properties but also increases the ThMn12 phase fraction by suppressing the formation of the α-Fe impurity phase. The optimal composition, Sm(Fe0.8Co0.2)10V2, exhibits a significant improvement across all key metrics: its ThMn12 phase purity reaches a maximum of 98.9 wt.%, its Curie temperature (TC) is elevated by 110 K to 735 K, and its magnetization (μ0M6T) peaks at 0.94 T. Easy- and hard-axis magnetization curves of oriented powders further indicate that the effective anisotropy decreases with increasing Co content. Furthermore, the optimized sample exhibits superior magnetic homogeneity, evidenced by the steepest initial magnetization curve. This work clarifies how Co substitution can simultaneously improve the apparent phase purity of the ThMn12 phase and the intrinsic magnetic performance in V-stabilized Sm-Fe systems. The findings provide guidance for the rational design of next-generation rare-earth-lean magnets with optimized properties.