Peculiar behavior of V on the Curie temperature and anisotropy field of SmFe_12-xV_x compounds

The effect of V on the phase stability and intrinsic magnetic properties of SmFe_12-xV_x (0 ≤ x ≤ 1.9) thin films, and bulk SmFe_12-xV_x (x = 1.5 and 2) are investigated. It is found that V help to stabilize the ThMn₁₂-type phase by decreasing the lattice parameters c and the c/a ratio up to its solid solubility limit x = 1.4. Above this limit, the formation of Sm-rich phase has been observed in the microstructure. Interestingly, Curie temperature (T_c) and anisotropy field (μ₀H_a) do not exhibit the same trend with the magnetization (μ₀M_s) where increasing V enhances the two quantities while decreasing the magnetization. The T_c increase from 533 K for x = 0 up to 660 K for x = 1 agrees with first principles calculation and it is related with the strengthening of the effect of Fe-V coupling along with its surrounding Fe-Fe couplings. Preservation of room temperature anisotropy field between 10 and 12 T is confirmed by micromagnetic simulation. In addition, V-substituted compounds demonstrate a higher μ₀H_a than SmFe₁₂ and Nd₂Fe₁₄B in the temperature range of 300–550 K. A comparison of the phase stabilizing elements M = Ti, Ti_0.5V_0.5, and V in SmFe₁₁M₁ reveals that V yields the highest μ₀M_s, μ₀H_a, and T_c. This study demonstrates that V-substituted compounds with 7 at.% phase stabilizers have more merit than Ti-substituted ones for the development of high-performance magnet with better extrinsic magnetic properties.