Improving the ferromagnetic exchange coupling in hard τ-Mn53.3Al45.0C1.7 and soft Mn50B50 magnetic alloys

To improve the magnetic properties of the hard-magnetic phase $$\tau $$ -Mn53.3Al45.0C1.7, it was mixed with different quantities of the soft magnetic phase Mn50B50 and annealed at different temperatures. Micrometric powders of the τ phase and the soft magnetic phase were mixed using solid-state procedures. The resulting magnetic properties were as follow: for the hard phase was saturation magnetization of Ms = 38.22 Am2kg−1 at 1.8 T, remanent magnetization of Mr = 20.10 Am2kg−1, coercive force of μ0Hc = 0.378 T, and maximum energy product of (BH)max = 3.09 kJm−3, and for the soft phase was Ms = 85.51 Am2kg−1 and a μ0Hc = 0.018 T. After the preparation of different compositions of the mixture, and their annealing at different temperatures, it was concluded that the sample MnAlC/MnB with 2 wt.% of MnB phase annealed at 400 ℃ is the best one. Its magnetic properties were Ms = 68.82 Am2kg−1 at 3.0 T, Mr = 36.26 Am2kg−1, μ0Hc = 0.373 T and (BH)max = 9.79 kJ m−3 which displays an improvement of about 7 kJ m−3 when compared to the original τ phase. Therefore, these magnetic properties are better than those shown by the pure τ phase. These properties were improved more when the sample was previously aligned and measured in parallel to the applied field.