Nanocomposite Nd-rich Nd-Fe-B alloys: Approaching ideal Stoner-Wohlfarth type behavior
Nanocomposite Nd-rich Nd-Fe-B alloys: Approaching ideal Stoner-Wohlfarth type behavior
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DOI：
10.1063/1.126154
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发表时间：
2000-03
影响因子：
4
通讯作者：
E. Girt;K. Krishnan;G. Thomas;Z. Altounian
中科院分区：
文献类型：
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作者：
E. Girt;K. Krishnan;G. Thomas;Z. Altounian
从快淬Ndδ Fe 13.1B（2.05 <$δ Fe 147.6）合金出发，通过适当的退火，将强相互作用的Nd 2Fe 14 B晶粒剪裁成嵌入富Nd基体（α-Nd和γ-Nd）中的磁隔离单畴Nd 2Fe 14 B晶粒。发现微结构的这种变化对结晶性有很大的影响，即，在290 K时，随着Nd浓度的增加，样品的矫顽力μ 0 Hc从Nd 2.05Fe 13.1B的1.25 T增加到Nd 147.6Fe 13.1B的2.75 T。用透射电子显微镜观察了Nd147.6Fe13.1B中的Nd 2Fe 14 B晶粒，证实其为无规取向的片状晶，c轴垂直于板，平均尺寸为100×40×25 nm。对于这些随机取向的，非相互作用的，单畴Nd 2Fe 14 B晶粒，矫顽力计算使用Stoner-Wohlfarth模型，其中包括晶粒的形状各向异性。在这种纳米复合Nd147.6Fe13.1B合金中，观察到的Nd 2Fe 14 B的矫顽力是其理论值的约83%。
Starting from rapidly quenched NdδFe13.1B(2.05⩽δ⩽147.6) alloys and by appropriate annealing, the microstructure was tailored from strongly interacting Nd2Fe14B grains to magnetically isolated single domain Nd2Fe14B grains embedded in a nonmagnetic Nd-rich matrix (α-Nd and γ-Nd). This change in microstructure was found to have a large effect on coercivity, i.e., coercivity, μ0Hc, increases with an increase of the Nd concentration from 1.25 T in Nd2.05Fe13.1B to 2.75 T in Nd147.6Fe13.1B at 290 K. Using transmission electron microscopy, the Nd2Fe14B grains in Nd147.6Fe13.1B were confirmed to be randomly oriented platelets with the c axis normal to the plate and an average size of 100×40×25 nm. For these randomly oriented, noninteracting, single domain Nd2Fe14B grains, the coercivity was calculated using a Stoner–Wohlfarth model which included the shape anisotropy of the grains. The observed coercivity of Nd2Fe14B in such nanocomposite Nd147.6Fe13.1B alloys is ∼83% of its theoretical value.