Magnetic Aftereffect of Nd-Fe-Co-B-V Compression Bonded Magnets

Compression bonded magnets were manufactured using melt-spun ribbons of Nd11Fe72Co8B7.5V1.5, MQP-B and MQP-D (GM Co., Ltd.). The magnetic field and temperature dependences of the magnetic aftereffect constant (Sv) which determines the magnetic stability were studied. Compared with bonded magnets based on MQ powders, Nd11Fe72Co8B7.5V1.5 bonded magnets had a larger (BH)max but a smaller Sv (2.3 kA/m). The temperature dependence of Sv for Nd11Fe72Co8B7.5V1.5 bonded magnets was better than that for Nd-Fe-B sintered magnets. The activation volumes (v) at room temperature of Nd-Fe-Co-B-V, MQP-B and MQP-D bonded magnets were approximately 18×10^¿25, 15×10^¿25 and 18×10^¿25 m³, respectively. The relation among HcJ, Sv and v (the Barbier plot) was studied for these Nd-Fe-B system compression bonded magnets, as well as for Sm2Co17 sintered magnets and Sm2Co17 system compression bonded magnets, in which magnetization reversal is by the same pinning mechanism. From the results of Barbier plots it was found that the relation between In Sv and In HcJ is linear, and that HcJ is proportional to v^¿0.6.