Ca2+占位与晶界重构对M型铁氧体结构及磁性演化行为的研究

This project is armed at the research on the structure and magnetic evolution behavior of M-type ferrites by Ca2+ occupancy and grain boundary reconstruction. The research contents include as fellows: Firstly, preparation of M-type hexagonal ferrites with CaLaCo co-substitution having a high magnetocrystalline anisotropy field (Ku1), good squareness ratio (Hk/Hcj), large remanence Br and maximum energy product （BH）max; Secondly, its structure evolution of the R block （AFe6O112-） and spinel S block （Fe6O82+） in the lattice of Ca/La/O stack and M-type ferrimagnetic super-exchange mechanism; Thirdly, the internal relations of magnetocrystalline anisotropy and saturation magnetization with Ca2+ occupancy; Finally, in combination with micro-magnetism, the grain boundary reconstruction and magnetic domain evolution behavior of the high-performance magnet. The Ca2+ occupancy with a small atomic radius，the occupation of magnetic Fe2+ and Co2+, the physical mechanism of the exchange of five magnetic ions, and the structural nature of less than 6 in AO•nFe2O3 system were investigated by means of Mössbauer and nuclear magnetic resonance. It is of great significance for this project to understand three scientific issues: the realization condition and law of M-type hexagonal ferrite with CaLaCo co-substitution, the contribution of the exchange between five sub-crystallites to the anisotropy and saturation magnetization, and the domain evolution with a high permanent magnet.

本项目针对Ca2+占位与晶界重构对M型铁氧体结构及磁性演化行为的研究。包括：1. 高磁晶各向异性Ku1、高矩形比 Hk/Hcj、剩磁Br和最大磁能积（BH）max的CaLaCo取代M 型铁氧体材料制备。2. Ca/La/O堆垛的晶格中R块（AFe6O112-）与尖晶石S块（Fe6O82+）的演化与M型亚铁磁性超交换机制。3. Ca2+占位与磁晶各向异性和饱和磁化强度的内在联系。4. 结合微磁学，研究CaLaCo取代M 型磁体的晶界重构与磁畴演化行为。采用Mössbauer和核磁共振等手段研究半径远小于Sr2+的Ca2+的占位、Fe2+和Co2+的分布、五个磁性离子的交换作用物理机制，以及Ca2+取代AO•nFe2O3体系中n远小于6的结构本质。研究在于解决高性能M型铁氧体的实现条件及规律认识，次晶位间交换作用对各向异性和饱和磁化强度的贡献，磁畴的演化与磁性能间所关联的三个重要的科学问题。

本项目针对高性能永磁铁氧体材料制备及其关联物理机制展开了研究。研究内容包括：1. Ca2+占位与晶界重构对M型铁氧体结构及磁性演化行为对高磁晶各向异性Ku1、高矩形比 Hk/Hcj、剩磁Br和最大磁能积（BH）max的影响。2.磁晶各向异性的物理起源及其与Mr/Ms和磁畴间作用关系研究。3. Ca/La/O堆垛的晶格中R块（AFe6O112-）与尖晶石S块（Fe6O82+）的演化与显微结构、磁晶各向异性及磁畴形态间关系研究。4. 研究了SrM的磁畴结构，明确关键磁参数与磁畴尺寸间作用关系。.项目研究解决了高性能SrM的实现条件，加深了磁性起源以及其演化行为的认识，揭示了磁晶各向异性Ku1和磁畴有序对Mr/Ms、剩磁Br和最大磁能积（BH）max间关联的科学问题的物理本质。.本项目已开发出高性能稀土掺杂永磁铁氧体，综合磁性能（HcJ + (BH)max）≥10.6，其中HcJ≥5.6 kOe，(BH)max≥5.0 MGOe，Hk/HcJ≥91%。径向收缩率SHR=13±0.5%，耐击穿电压V-AC≥1.8 kV。已在相关企业得到验证，并批量生产。