Computer simulation of the effect of an ultra soft phase on the magnetic properties of nanocrystalline permanent magnets
Computer simulation of the effect of an ultra soft phase on the magnetic properties of nanocrystalline permanent magnets
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DOI：
10.1016/s0304-8853(01)00317-1
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发表时间：
2001-09
影响因子：
2.7
通讯作者：
M. K. Griffiths;J. Bishop;J. Tucker;H. Davies
中科院分区：
文献类型：
--
作者：
M. K. Griffiths;J. Bishop;J. Tucker;H. Davies
对由硬磁单轴相（以Nd_2Fe_（14）B为代表）和超软相（以α-Fe为代表）组成的随机取向、交换耦合纳米晶组装体的微磁模型进行了数值研究。硬微晶位于三维立方晶格上，并且软相的立方微晶插入在每组八个硬微晶的连接处。退磁曲线作为一个静态平衡状态的序列，在一个增量变化的外加磁场。的矫顽力，剩磁和能量积的值被报告为ΔGH，硬相的晶粒尺寸，和的Δ GH S，软相的分数体积的函数。随着Δ S的增加，对Δ GH的依赖性下降得相当快。模型中α铁的低各向异性和高饱和磁化强度对剩磁增强的贡献大致相等。其剩磁值与含α-Fe的Nd_2Fe_（14）B的实验值符合得很好。然而，它的矫顽力和能量积的值，虽然明显低于其他一些作者通过计算获得的值，但明显超过了实验获得的值，但显示出与ΔGHand Δ S相似的变化。
Micromagnetic models of assemblies of randomly oriented, exchange coupled, nanocrystals consisting of a magnetically hard uniaxial phase (typified by Nd2Fe14B) together with an ultra-soft phase (typified by α-iron) have been studied numerically. The hard crystallites were located on a three dimensional cubic lattice, and cubic crystallites of the soft phase were inserted at the junctions of every group of eight hard crystallites. Demagnetizing curves were obtained as a sequence of static equilibrium states in an incrementally changing applied field. Values of the coercivity, remanence and energy product are reported as functions of ΔGH, the grain size of the hard phase, and of ϕS, the fractional volume of the soft phase. The dependence on ΔGHfalls quite rapidly with increasing ϕS. The low anisotropy and high saturation magnetization of the α-iron make approximately equal contributions to remanence enhancement in the model. Its remanence values are in quite good agreement with experimental values for Nd2Fe14B containing α-iron. However, its values for the coercivity and energy product, though decidedly lower than those obtained computationally by some other authors, significantly exceed those obtained experimentally, but show a similar variation with ΔGHand ϕS.