Intergranular exchange interaction in nanocrystalline hard magnetic rare earth–iron–boron-based melt-spun alloy ribbons
Intergranular exchange interaction in nanocrystalline hard magnetic rare earth–iron–boron-based melt-spun alloy ribbons
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DOI：
10.1088/0022-3727/42/14/145006
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发表时间：
2009-06
期刊：
影响因子：
--
通讯作者：
Z. W. Liu;H. Davies
中科院分区：
文献类型：
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作者：
Z. W. Liu;H. Davies
采用快淬法制备了具有高硬磁性能的快速凝固纳米晶RE（Fe/Co）B（RE = Nd，Pr）合金。通过对磁化和退磁曲线、特征回线和Henkel图的分析，研究了工艺、成分、相组成、显微结构和温度对纳米晶间交换作用的影响。均匀的单相行为，观察到单相和纳米复合合金与细纳米晶粒，最佳的熔体旋转加工生产。结果表明，通过构建汉克尔图，减少硬相晶粒尺寸增强交换耦合。此外，通过逐渐降低RE：（Fe/Co）比，在2/14/1纳米晶体基质内引入和增加软相微晶的体积分数，也增加了交换耦合的强度，这通过Henkel图中正峰的增加的高度来证明。在升高的温度下，由于交换长度的增加（Lex =（A/K）1/2），交换耦合进一步增强，尽管各向异性常数K和交换常数A都随着温度的升高而降低。基于畴反转和双畴形核机制的修正Brown方程中的微结构参数分析表明，Co替代Fe和软α-（FeCo）纳米晶的引入不仅降低了与晶界粗糙度相关的杂散场效应，而且增强了相邻纳米晶之间的交换耦合。
Rapidly solidified nanocrystalline RE(Fe/Co)B (RE = Nd,Pr) alloys with enhanced hard magnetic properties were obtained by melt spinning. The effects of processing, composition, phase constitution, microstructure and temperature on the exchange interaction between nanocrystallites were studied by analysing the magnetization and demagnetization curves, characteristic loops and Henkel plots. Uniform single phase behaviour was observed for single phase and nanocomposite alloys with fine nano-grains, produced by optimum melt spin processing. It was shown, by constructing Henkel plots, that decreasing the hard phase grain size enhances the exchange coupling. Also, introducing and increasing the volume fraction of soft phase crystallites within the 2/14/1 nanocrystalline matrix, by progressively reducing the RE:(Fe/Co) ratio, also increased the strength of the exchange coupling, which was manifested by increased height of the positive peak in the Henkel plot. At elevated temperatures, the exchange coupling was further enhanced due to an increased exchange length (Lex = (A/K)1/2), in spite of the fact that both the anisotropy constant K and the exchange constant A decrease with increasing temperature. Analysis of the microstructure parameters in the modified Brown equation, based on a nucleation mechanism of domain reversal and coercivity, indicate that Co substitution for Fe and introduction of soft α-(FeCo) nanocrystallites not only reduce the stray field effects associated with grain boundary roughness but also enhance the exchange coupling between neighbouring nanograins.