Evolution of interface structure ofα−Fe/Nd2Fe14Bnanocomposites prepared by crystallization from the amorphous alloy
Evolution of interface structure ofα−Fe/Nd2Fe14Bnanocomposites prepared by crystallization from the amorphous alloy
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DOI：
10.1103/physrevb.66.212103
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发表时间：
2002-12
影响因子：
3.7
通讯作者：
X. Zhang;Y. Guan;Jingwu Zhang;W. Sprengel;K. J. Reichle;K. Blaurock;K. Reimann;H. Schaefer
中科院分区：
文献类型：
--
作者：
X. Zhang;Y. Guan;Jingwu Zhang;W. Sprengel;K. J. Reichle;K. Blaurock;K. Reimann;H. Schaefer
用正电子湮没技术研究了非晶Nd 9 Fe 83 Co 3 B 5晶化制备的α-Fe/Nd 2Fe 14 B纳米复合材料的界面结构演变。正电子寿命研究表明，在700°C下制备的α-Fe/Nd 2Fe 14 B纳米复合材料中存在两种界面结构一个特征在于由正电子寿命为155 ps的被确定为具有密集堆积结构的界面非晶层。另一种具有更松散的原子结构，具有空位大小的自由体积。随着退火温度的升高，非晶层的体积分数逐渐减小，当退火温度T≥950°C时，非晶层只保留有空位的界面结构。正电子-电子湮没γ量子的符合多普勒展宽研究表明，在700°C下制备的纳米复合材料中，大尺寸的界面自由体积主要被Nd和B原子包围，这被认为削弱了纳米复合材料中微晶之间的磁交换耦合。
The evolution of interface structure of α-Fe/Nd 2 Fe 1 4 B nanocomposites prepared by crystallization of amorphous Nd 9 Fe 8 3 Co 3 B 5 has been investigated by employing positron annihilation techniques. Positron lifetime studies show that there are two kinds of interface structures in the α-Fe/Nd 2 Fe 1 4 B nanocomposites prepared at 700°C. One characterized by a positron lifetime of 155 ps is determined to be the interfacial amorphous layer with a densely packed structure. The other has a more loosely packed atomic structure with vacancy-sized free volumes. The volume fraction of the amorphous layer decreases with increasing annealing temperature and only the interface structure with vacancies is retained after annealing at temperatures T≥950°C. Coincident Doppler broadening studies of the positron-electron annihilation y quanta show that the interfacial free volumes with a large size in the nanocomposites made at 700°C are predominantly surrounded by the nonmagnetic atoms Nd and B, which is believed to weaken the magnetic exchange coupling between the crystallites in the nanocomposites.