Micromagnetism and microstructure of hard magnetic materials
Micromagnetism and microstructure of hard magnetic materials
复制标题
DOI：
10.1088/0022-3727/29/9/008
复制
发表时间：
1996-09-14
影响因子：
3.4
通讯作者：
Zern, A
中科院分区：
文献类型：
--
作者：
Kronmuller, H;Fischer, R;Zern, A
高性能磁性材料的基础是优异的固有磁性能和优化的微观结构和合金成分。这三个参数之间的相互作用一般是相当复杂的，不能明确处理的微磁学理论。相反，必须应用数值方法来确定磁滞回线的特性。在计算微磁学（纳米磁学）的框架内，使用有限元方法的矫顽场的不同类型的晶粒系综已被确定。在纳米晶复合材料的情况下，晶粒尺寸，交换和偶极耦合之间的作用将被详细讨论。结果表明，在烧结磁体中，大矫顽力需要晶粒之间的磁解耦，而具有交换耦合的区域急剧降低矫顽场，但是，然而，增加剩磁。具有剩磁增强和高矫顽力的纳米晶复合材料需要直径为硬磁相壁宽两倍的软晶粒。对于mu（0）H（C）= 0.75 T的50% α-Fe磁导率的量，预期剩磁为1.5 T，能量积（BH）（max）= 450 kJ m（-3）。对数值结果进行了定量分析，发现He和剩磁与晶粒尺寸呈对数关系。
High-performance magnetic materials are based on outstanding intrinsic magnetic properties and optimized microstructures and alloy compositions. The interactions between these three parameters in general are rather complex and cannot be treated explicitly by the theory of micromagnetism. Instead numerical methods have to be applied in order to determine the characteristic properties of hysteresis loops. Within the framework of computational micromagnetism (nanomagnetism) using the finite-element method the coercive fields of different types of grain ensembles have been determined. In the case of nanocrystalline composites the roles of grain size, exchange and dipolar coupling between grains will be discussed in detail. It is shown that, in sintered magnets, large coercivities require magnetic de-coupling between the grains, whereas regions with exchange coupling reduce the coercive field drastically, but, however, increase the remanence., Nanocrystalline composite materials with remanence enhancement and high coercivities are shown to require soft grains with diameters of twice the wall width of the hard magnetic phase. For an amount of 50% alpha-Fe coercivities of mu(0)H(C) = 0.75 T, a remanence of 1.5 T and an energy product of (BH)(max) = 450 kJ m(-3) are expected. A quantitative analysis ct the numerical results for He and the remanence leads to logarithmic dependences on grain size.