COERCIVE FORCE MECHANISM DERIVED FROM THE RELATION BETWEEN Nd_2Fe_(14)B GRAIN ALIGNMENT AND COERCIVE FORCE DECREASE RATIO IN NdFeB SINTERED MAGNETS

摘要

It was found that the coercive force of NdFeB sintered magnets decreases as the Nd_2Fe_(14)B grain alignment improves. Because of these phenomena, studies looked at the relation between this alignment and the coercive force decrease ratio, which is defined as (H_(cJ) -H_(cJisotropy)) / H_(cJisotropy) where H_(cJ) is the aligned magnet coercive force and H_(cJisotropy) is the coercive force of isotropic magnets. In experiments, it was expected that the coercive force of perfectly aligned magnet reached to 0.7 of H_(cJisotropy). When it is postulated that coercive force is determined by the Stoner-Wohlfarth magnetization rotation model, coercive force increases as the alignment improves and it becomes difficult to explain our experimental data. A value of 1/√2 of H_(cJisotropy) was obtained from the magnetic domain wall motion model. This value was very close to our data. It strongly suggests that the coercive force of NdFeB sintered magnets is determined by domain wall motion.