Magnetic properties of high-coercivity melt-spun Pr-Fe-Co-Ti-B-Si system ribbons and their bonded magnets

Melt-spun ribbons of Pr_xFe_98-x-y-zCo_yTi_1.5B_zSi_0.5(x=10.0 -13.0, y=8.0 -12.0, z=7.0 - 14.0) alloys were prepared by the single roller liquid rapid-quenching method, and the effects of composition, wheel velocity, and annealing condition on the magnetic properties were studied. The optimum preparation conditions and some of the properties were as follows: composition: Pr₁₁Fe_68.5 Co formula₈Ti_1.5B_10.5Si_0.5; wheel velocity: 10.0 m/s and annealing condition 600°C for 5 min in Ar atmosphere; magnetic properties J_r=0.8 T (8.0 kG), H_cJ=1.57 MA/m (19.7 kOe), H_cB=0.55 MA/m(6.9 kOe), (BH)_max=111.2 kJ/m³ (13.9 MGOe), H_k/H_cJ×100=24.9%, α(J_r)=-04%/°C, α(H_cJ)=-0.37%/°C and T_c=403°C. From a TEM observation, the average particle size of this ribbon was found to be about 23 nm. The isotropic compression molding bonded magnets were prepared by using Pr₁₁Fe_68.5Co₈Ti_1.5B_10.5Si_0.5 ribbons annealed at 600°C for 5 min. The magnetic properties of this bonded magnet were J_r=0.60 T(6.0 kG), H_cJ=1.53 MA/m(19.3 kOe), H_cB=0.42 MA/m (5.2 kOe) and (BH)_max=66.8 kJ/m³ (8.4 MGOe). The irreversible losses of Pr₁₁Fe_66.5Co₁₀Ti_1.5B_10.5Si_0.5 and Pr₁₁Fe_64.5Co₁₂Ti_1.5B_10.5Si_0.5 bonded magnets were smaller than that of an MQP-O bonded magnet at 150°C.