Maximizing the hard magnetic properties of melt-spun Ce–La–Fe–B alloys

To balance the utilization of rare earth (RE) resource and develop Ce-based permanent magnets with high performance/cost ratio, the role of La substitution in the melt-spun (Ce_1−xLa_x)_yFe₁₄B (x = 0–0.4, and 0.5; y = 2–4) alloys has been investigated. It has been confirmed that the hard magnetic properties of Ce-based magnets can be effectively enhanced by partial substitution of La. The maximum (BH)_max of (Ce,La)–Fe–B alloys can be obtained at a Ce:La atomic ratio of 7:3. The lattice parameters and Curie temperature of the hard magnetic (Ce/La)₂Fe₁₄B phase increase linearly with increasing La content. Three different alloy systems with y = 2, 2.5 and 3 show similar behavior of magnetic properties dependences on La. In the RE-rich compositions, La substitution for Ce can effectively inhibit the precipitation of the CeFe₂ phase. A solid solution, Ce(La) phase with a space group of Fm-3m, appears in the (Ce_0.7La_0.3)_yFe₁₄B alloys with y ≥ 3.5. A good combination of magnetic properties with H_cj = 345 kA/m, J_5T = 1.03 T, J_r = 0.60 T, and (BH)_max= 6.3 MGOe is obtained in (Ce_0.7La_0.3)_2.5Fe₁₄B alloy. In addition, 30 at.% La substitution for Ce can significantly refine the grains, resulting in the enhancement of exchange coupling interaction. The present finding is beneficial for designing new and low-cost magnetic materials.