Stress, strain and technical magnetic properties in `exchange-spring' Nd2Fe14B + α-Fe nanocomposite magnets
Stress, strain and technical magnetic properties in `exchange-spring' Nd2Fe14B + α-Fe nanocomposite magnets
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DOI：
10.1088/0022-3727/34/5/313
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发表时间：
2001-03
期刊：
影响因子：
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通讯作者：
L. H. Lewis;A. Moodenbaugh;D. Welch;V. Panchanathan
中科院分区：
文献类型：
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作者：
L. H. Lewis;A. Moodenbaugh;D. Welch;V. Panchanathan
一种改进的Williamson-Hall分析被应用到同步辐射透射X射线衍射数据获得的一系列的三个熔纺磁性纳米复合材料的“交换弹簧”的Nd 2Fe 14 B和不同的量的α-Fe范围从0-32体积%。数据的分析表明，在Nd 2Fe 14 B相中没有来自微应变或其他晶格畸变的可测量的贡献。该结果表明，Nd 2Fe 14 B布拉格峰展宽仅由颗粒尺寸（在440 A的数量级上）引起，并且熔融淬火的Nd 2Fe 14 B晶粒的形状近似为球形。相比之下，α-Fe相表现出布拉格峰展宽，这可能归因于各向异性应变和颗粒尺寸展宽效应的组合。α-Fe相的平均颗粒尺寸为360 A，明显大于由Scherrer公式确定的尺寸，并且α-Fe颗粒的平均应力（推断为拉伸的）约为1 GPa，其转化为约0.1%的rms应变= e21/2。这些结果提供了一个物理基础，以解释这两个边缘交换派生的剩磁增强和异常的高温超导合金中发现。
A modified Williamson-Hall analysis was applied to synchrotron transmission x-ray diffraction data obtained for a series of three melt-spun magnetic nanocomposite `exchange-spring' materials comprised of Nd2Fe14B and varying amounts of α-Fe ranging from 0-32 vol%. Analysis of the data demonstrates that there is no measureable contribution from microstrains or other lattice distortions in the Nd2Fe14B phase. This result indicates that the Nd2Fe14B Bragg peak broadening arises from particle size only (on the order of 440 A) and that the shape of the melt-quenched Nd2Fe14B grains is approximately spherical. In contrast, the α-Fe phase exhibits Bragg peak broadening that may be attributed to a combination of both anisotropic strain and particle-size broadening effects. The average particle size of the α-Fe phase is 360 A, significantly larger than that determined from the Scherrer formula, and the average stress, deduced to be tensile, of the α-Fe particles is approximately 1 GPa, which translates to an rms strain = e21/2 of approximately 0.1%. These results provide a physical basis to explain both the marginal exchange-derived remanence enhancement and the anomalous elevated-temperature coercivities found in these alloys.