在热退磁状态,这种永磁体的基体晶粒一般为多畴结构,单个畴为180°片状畴,也有少量钉形畴和迷宫畴。测得平均畴宽为1.5μm。还观察到一些直径1μm左右的单畴晶粒和极个别直径3μm左右的单畴晶粒,计算出畴壁能γ=36mJ/m~2,交换常数A=4.5×10~(-11)J/m,畴壁厚度δ=15.7nm,临界单畴晶粒直径D_c=0.5μm。还讨论了晶界附近存在高磁场梯度与晶界两侧相邻磁畴内磁化方向的关系和微观组织对K,A和δ值的影响。
In a thermally demagnetized state, the matrix grains in (NdPr)_(16)Fe_(76)B_8 permanent magnet, in general, are the multidomain structure, i. e., 180°plate-like individual domain and a few spike-like or mazelike domains. The averagewidth of domains is measured as 1.5μm. The grain size of single-domain is observedto be some about 1μm and particularly up to 3μm. The calculated domainwall energy, γ=3.6 MJ/m~2, the exchange constant, A=4.5×10~(-11)J/m, the domainwall width, δ=15.7nm, and the critical grain diameter of single-domain, D_c=0.5μm. The dependence of high magnetic field gradient near grain boundaries on differentmagnetization direction in the adjacent magnetic domains on the both sides of grainboundaries as well as the effect of microstructure on the values of K, A and δwere also discussed.
参考文献
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