Magnetic Properties of Melt-Spun Pr(Nd)-Fe-Co-Nb-Cu-Si-B System Ribbons and their Bonded Magnets

Melt-spun ribbons of Pr-Fe-Co-Nb-Cu-Si-B system alloys were prepared by single roller rapid-quenching method. Effects of composition,wheel velocity and heat-treatment on magnetic properties were investigated. The optimum preparation conditions of compounds were as follows: composition Pr₉Fe_68.5Co₁₀Nb₁Cu_0.5Si_0.5B_10.5 wheel velocity 12.5 m/s; heat-treatment 625 °C for 5 min. Magnetic properties obtained were (BH)_max = 121.8 kJ/m³, J_r = 0.90 T, H_cJ = 898.7 kA/m, and H_cB = 509.0 kA/m. Temperature coefficients of J_r and H_cJ of the ribbons of Pr₉Fe_68.5Co₁₀Nb₁Cu_0.5Si_0.5B_10.5 alloy were α(J_r)_ave = -0.034 %/°C and α(H_cJ) = -0.290 %/°C, respectively. The value of (BH)_max for the isotropic Pr₉Fe_68.5Co₁₀Nb₁Cu_0.5Si_0.5B_10.5 bonded magnet prepared by using ribbons annealed at 625 °C for 5 min is 84.4 kJ/m³. Irreversible loss of the bonded magnet is -2.74 % (at 125°C).