Effect of the grain alignment of Nd-Fe-B sintered magnets on the coercive force

Grain alignment is one of a factor affecting coercive force in Nd-Fe-B sintered magnets. Relation between degree of alignment and coercive force was evaluated using Br/Js as the degree of grain alignment. It was found that the coercive force decreases with alignment increase in highly aligned region. The decrease ratios of coercive force with various alignments to the isotropic magnet's coercive forces are on the same line even though they have different coercive force due to different composition in isotropic aligned state. Extrapolating this line to perfectly aligned magnet, coercive force of perfectly aligned magnet reaches to - 30% of coercive force of the isotropic oriented magnets. It is found that this coercive decrease ratio behavior is similar even in ferrite magnets. We estimate coercive force of perfectly aligned magnets from isotropic magnet and obtained 1/√ (0.70) of isotropic magnet's coercive force which is agrees well to our experimental result.