Dynamic magnetization observations and reversal mechanisms of sintered and die-upset Nd-Fe-B magnets
Dynamic magnetization observations and reversal mechanisms of sintered and die-upset Nd-Fe-B magnets
复制标题
烧结和模镦 Nd-Fe-B 磁体的动态磁化观察和反转机制
DOI：
10.1016/s0304-8853(00)00195-5
复制
发表时间：
2000
影响因子：
2.7
通讯作者：
Yan Zhu
中科院分区：
文献类型：
--
作者：
V. Volkov;Yan Zhu
采用原位TEM磁化实验，结合菲涅耳模式和福柯模式下的洛伦兹显微镜，研究了烧结多晶Nd-Fe-B磁体磁化反转的局部特征。模镦（DU）磁体的晶粒织构沿c轴排列良好，而烧结（SI）磁体的晶粒取向分布更广。尽管磁滞曲线相似，但它们在纳米尺度上的磁化反转行为却大不相同。控制du磁体反转的主要机制是反向畴的成核，优先发生在错向晶界处，其次是晶界处的畴壁钉住。相比之下，硅磁体的磁化逆转首先是在高磁场下主要在错向晶粒中通过反畴偶极子的形核和扩展进行的，然后是在更负的磁场下通过在顺向晶粒晶界附近的磁畴的形核和分裂进行的主要不可逆过程。这个过程是通过新创建的域壁的横向扩展来完成的。讨论了在du磁体中观察到的强钉夹中心的一个简单模型。
In situ TEM magnetizing experiments combined with Lorentz microscopy in Fresnel and Foucault mode were used to study local features of magnetization reversal in polycrystalline sintered and die-upset Nd–Fe–B magnets. The die-upset (DU) magnets featured well-aligned grain texture along the c-axis, while the sintered (SI) magnets have a much wider distribution of grain orientations. Despite the similarity of the hysteresis curves, we found their nanoscale behavior of the magnetization reversal was quite different. The predominant mechanism controlling reversal in DU-magnets was nucleation of reversed domains, preferentially at misaligned grain interfaces, followed by domain wall pinning at grain boundaries. In contrast, magnetization reversal in SI-magnet progressed first by nucleation and expansion of reversed domain dipoles predominantly in misaligned grains at a high magnetic field, and then by the major irreversible process via nucleation and splitting of magnetic domains near the grain boundaries of well-aligned grains at more negative fields. This process is completed with lateral expansion of newly created domain walls. A simple model for the strong pinning–trapping centers observed in DU-magnets is discussed.
影响因子：
3.2
作者：
SAGAWA, M;FUJIMURA, S;MATSUURA, Y
通讯作者：
MATSUURA, Y