交换耦合作用
(1. 西安交通大学 理学院材料物理系， 西安 710049；
2. 南京大学 物理系， 南京 210093)
摘 要: 用熔体快淬法制备了高性能纳米双相耦合Nd2Fe14B/α-Fe磁体，研究了快淬速率对其微结构和交换耦合作用的影响。 实验结果表明， 控制快淬速率在12m/s时， 可直接得到显微组织均匀， α-Fe相粒子细小且均匀分布的纳米双相耦合Nd2Fe14B/α-Fe磁体。低温退火消除由快速凝固带来的成分不均匀性后， 强烈的铁磁交换耦合作用导致其最高磁性能为： iHc=432.2kA/m, Jr=1.08T, (BH)max=115kJ/m3。 快淬速率提高，非晶相体积分数增加， 在高温晶化热处理时软硬磁相析出不均匀， 个别α-Fe相粒子奇异长大， 尺寸达到100nm左右，这不利于软硬磁相间的交换耦合作用， 有损磁性能。
关键字: 纳米复合磁体; 交换耦合作用; 微结构;矫顽力
Nd2Fe14B/α-Fe magnets
（1. Department of Physical Materials, School of Science, Xi’an Jiaotong University,Xi’an 710049, China;
2. Department of Physics, Nanjing University, Nanjing 210093, China）
Abstract:Nanocomposite Nd2Fe14B/α-Fe magnets are synthesized by melt-spinning a Nd8Fe86B6 alloy and the effect of wheel speed on the microstructure and exchange coupling interaction is investigated. The results show that there is an optimum wheel speed about 12m/s at which a homogeneous Nd2Fe14B/α-Fe microstructure with fine α-Fe grains is developed directly from the melt. After low temperature annealing, the non-uniform composition from amorphous is eliminated and the magnetic properties can increase. The maximum magnetic properties are: iHc=432.2kA/m, Jr=1.08T, (BH)max=115kJ/m3. However, higher wheel speed leads to the appearance of amorphous phase and its volume fraction increases with the increase of wheel speed. These result in a Nd2Fe14B/α-Fe structure with large α-Fe grains after a subsequent crystallization annealing, which deteriorates the exchange-coupling between Nd2Fe14B phase and α-Fe phase and decrease its magnetic properties.
Key words: nanocomposite magnets; exchangse coupling interaction; microstructure; coercivity
