Coercivity limits and mechanism in nanocomposite Nd-Fe-B alloys
Coercivity limits and mechanism in nanocomposite Nd-Fe-B alloys
复制标题
DOI：
10.1016/s0304-8853(01)00031-2
复制
发表时间：
2001-06
影响因子：
2.7
通讯作者：
E. Girt;K. Krishnan;G. Thomas;Erol Girt;Z. Altounian
中科院分区：
文献类型：
--
作者：
E. Girt;K. Krishnan;G. Thomas;Erol Girt;Z. Altounian
Nd-Fe-B系统中的最大矫顽力是通过系统地定制从强相互作用的Nd 2Fe 14 B晶粒到富Nd基体中的磁隔离的Nd 2Fe 14 B晶粒的微观结构来实现的。对Nd-Fe-B样品的晶体结构、相纯度和磁性能进行了全面的测试。特别是能量过滤图像，使用内壳层电离边缘的空间分辨测量，在评估颗粒形状（晶体学c轴垂直于板的血小板），尺寸（约100×40× 25 nm）和分布方面至关重要。对于随机取向的非相互作用粒子，观测到的最大磁化率μ 0 Hc = 2.75 T，是Stoner-Wohlfarth相干旋转行为（包括退磁效应）预期理论极限的1.83%。热退磁Nd-Fe-B样品的初始磁化曲线表明，随着Nd浓度的增加，磁化率有系统地增加，这是由于强相互作用的Nd 2Fe 14 B晶粒的贡献与晶粒尺寸小于或等于磁畴尺寸和完全孤立的多畴Nd 2Fe 14 B晶粒之间的竞争。讨论了Nd-Fe-B样品中可能的磁化机制。
The largest coercivity in the Nd–Fe–B system was achieved by systematically tailoring the microstructure from strongly interacting Nd2Fe14B grains to magnetically isolated Nd2Fe14B grains in a Nd-rich matrix. The crystal structure, phase purity and magnetic properties of the Nd–Fe–B samples were extensively measured. In particular energy-filtered images, using spatially resolved measurements of inner-shell ionization edges, was critical in evaluating the particle shapes (platelets with the crystallographic c-axis normal to the plate), size (∼100×40×25nm) and distribution. For randomly oriented, non-interacting particles, the largest observed coercivity, μ0Hc∼2.75 T is ∼83% of the theoretical limit expected for Stoner–Wohlfarth coherent rotation behavior including demagnetization effects. Initial magnetization curves of thermally demagnetized Nd–Fe–B samples show a systematic increase in susceptibility with an increase in Nd concentration as a result of a competition between contributions from strongly interacting Nd2Fe14B grains with grain sizes smaller or equal to the magnetic domain size and completely isolated multidomain Nd2Fe14B grains. The possible coercivity mechanisms in such Nd–Fe–B samples are discussed.