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以Nd2 Fe1 4B α Fe为例 ,采用立方体晶粒结构模型 ,研究了纳米复合永磁材料中不同磁性晶粒间的交换耦合相互作用和有效各向异性 .纳米复合永磁材料的有效各向异性Keff等于软、硬磁性相各向异性的统计平均值 ,每个晶粒的各向异性由晶粒表面交换耦合部分和晶粒内部未交换耦合部分的各向异性共同确定 .计算结果表明 ,软、硬磁性相晶粒尺寸分布显著地影响有效各向异性Keff的值 .当软、硬磁性晶粒尺寸D相同时 ,Keff随晶粒尺寸和硬磁性相体积分数的降低而减小 ,当D <2 0nm时 ,Keff随D的减小而急剧下降 ;在某一确定的软磁性晶粒尺寸下 ,Keff随硬磁性晶粒尺寸变化呈现极大值 ,Keff极大值对应硬磁性相的晶粒尺寸随着软磁性相体积分数的增加和软磁性晶粒尺寸的减小而减小 .Keff随晶粒尺寸的变化与矫顽力的变化规律大体一致 ,纳米复合永磁材料矫顽力的降低主要是由有效各向异性的降低引起的
Taking Nd2 Fe1 4B α Fe as an example, the cubic crystal structure model was used to study the exchange coupling interaction and effective anisotropy of different magnetic grains in nanocomposite permanent magnetic materials. The effective anisotropy of nanocomposite permanent magnetic materials Keff is equal to the statistical average of the anisotropy of the soft and hard magnetic phases, and the anisotropy of each grain is determined by the anisotropy of the exchange coupling part of the grain surface and the non-exchange coupling part of the grain. The calculation results show that the soft , The hard magnetic phase grain size distribution significantly affects the effective anisotropy Keff value.When the soft and hard magnetic grain size D is the same, Keff decreases with the decrease of the grain size and hard magnetic phase volume fraction, when D <2 0 nm, Keff decreases sharply with the decrease of D. At a certain soft magnetic grain size, Keff exhibits a maximum with the change of hard magnetic grain size, and the Keff maximum corresponds with the hard magnetic phase The grain size decreases with the increase of volume fraction of soft magnetic phase and the decrease of soft magnetic grain size.Keff changes with the variation of grain size and coercive force generally consistent, coercivity of nano-composite permanent magnetic material Lower main Effective to cause the reduction of anisotropy