多相变胞壁相改性2:17型SmCo磁体反常矫顽力研究

The discoveries of abnormal coercivity in 2:17 type SmCo magnets are helpful to exploit new ways for the preparation of magnets with high operating temperature or high temperature stability of coercivity. Their complex magnetic structures and magnetic behaviors also have a great theoretical research value. Traditionally, abnormal coercivities are achieved through regulating the content and distribution of non-magnetic Cu element within the cell boundaries. What is difference in this project, taking advantage of the character of spin-reorientation-transition in the cell-boundary-phase-like RCo5 (R=Dy, Tb, Nd) compounds, Dy, Tb, Nd are introduced into the cell boundary of magnets to enrich the phenomenon of abnormal coercivities. The influence laws of coercivity and its temperature dependence during the process of spin-reorientation-transition and paramagnetic-ferromagnetic transition will be analyzed. The coercivity mechanism of the magnets will be illuminated when their cell boundary phases are in easy-plane, easy-cone, easy-axis and paramagnetic state. Combined with the cognition of temperature dependence of abnormal coercivity, the physical mechanism of abnormal coercivity will be strengthened and a physical model will be built to explain the abnormal coercivity. The implementation of this project not only can promote the understanding of the coercive mechanism of 2:17 type SmCo magnet, but also will rise new ideas to develop magnets with high temperature stability of coercivity.

2:17型SmCo永磁体中反常矫顽力温度依赖关系的发现为提高磁体温度稳定性，发展高温永磁材料提供了新的研究思路，其中复杂的磁结构和磁化行为也具有极大的理论研究价值。与传统的通过调控非磁性Cu元素在胞壁相内的含量与分布获得反常矫顽力温度依赖关系不同，本项目利用类胞壁相RCo5(R=Dy, Tb,Nd )合金具有自旋再取向的特性，通过Dy、Tb、Nd的引入调控胞壁相自旋再取向行为，获得多样的反常矫顽力温度依赖关系，深入探讨多种胞壁相磁性相变行为对磁体矫顽力温度依赖性的影响规律，研究胞壁相为易面、易锥、易轴、顺磁状态下磁体的矫顽力机制，弄清反常矫顽力温度依赖关系与胞壁相磁相变间的深层次关系，建立解释反常矫顽力温度依赖关系物理机制的理论模型。该项目的实施将推进对2:17型SmCo磁体矫顽力机理的认识，为开发新型高矫顽力温度稳定性磁性材料提供新思路。

2:17型稀土永磁材料因具有纳米级的胞状组织结构，胞壁相磁性质对磁体矫顽力有着复杂的影响。本项目通过类胞壁相 Sm1-xRxCo5 (R=Dy，Nd，Tb)化合物的自旋再取向相变行为的研究，发现了随R的增加化合物的自旋再取向转变温度点向高温移动。进而利用Dy，Nd，Tb元素添加，制备了具有自旋再取向行为胞壁相的2:17型稀土永磁材料，在三种磁体中均发现了正矫顽力温度系数的反常现象。研究了磁体在胞壁相易面型、易轴型、铁磁态、顺磁态不同磁状态下，退磁曲线、回复曲线、矫顽力角度依赖性变化规律，表明主相形核场决定着矫顽力的大小（主相形核场机理）。理论认为：对于具有胞壁相自旋再取向转变行为的2:17型磁体，主相形核场主要受到三种杂散场的干扰：①类软磁胞壁相；②低畴壁能差；③热扰动。这三种场都会导致矫顽力降低，三种干扰因素的不同主导作用导致了矫顽力不同的温度依赖性特征。基于研究对矫顽力温度稳定性机理的突破，开发了自旋相变胞壁相调控矫顽力技术，制备出了双低温度系数Sm0.54(Gd0.625Er0.375)0.06Dy0.4(Co0.695Fe0.2Cu0.08Zr0.025)7.2磁体。其磁性能为Br=8.55 kGs , Hcj=6.97 kOe , (BH)max = 17.13 MGOe, α(RT, 100 °C)=0.003 %/°C，β(RT, 100 °C)=0.002 %/°C。较传统低剩磁温度系数2:17型SmCo磁体，在保证剩磁温度系数相当的情况下，矫顽力温度系数提高了2个数量级，而且磁能积也相当。该项目的完成加深了2:17型稀土永磁材料矫顽力机制的认识，丰富了矫顽力温度稳定性调控技术，开拓了双低温度系数的新型永磁材料，在未来精密仪器仪表领域有着广泛的应用前景。在执行期内共发表SCI论文7篇，申请发明专利6项，其中国际专利3项； 培养硕士生3人，培养博士生1人。