新型蜂窝状复合铁氧体的磁性能、交换耦合及微磁结构研究

Hexagonal M-type SrFe12O19 hard magnetic ferrite is widely used in many fields due to its fine chemical stability and high cost performance. It is an important way to improve the magnetic properties of hard magnetic ferrite by using the exchange coupling interaction between a hard magnetic phase and a soft magnetic phase to prepare composite ferrite with exchange spring. Theoretically, building a composite with a cellular structure is the best way to realize the exchange coupling between magnetic hard and soft phases. However, due to the difficulty of preparing this structure in experiment and the lack of both experimental and theoretical support from micromagnetism, the improvement of magnetic properties for composite ferrites is greatly limited. In this proposal, a common and a magnetic-field-induced hydrothermal method will be used to synthesize the ferrites, respectively. The soft magnetic phases with higher saturation magnetization, such as (Ni,Zn)Fe2O4, CoFe2O4 and so on, will be introduced into SrFe12O19 matrix to prepare cellular composites by using nanoscale C balls as the assistant, and the relationship between magnetic properties and the exchange coupling will be systematically studied. In addition, combined with the magnetic force microscopy, the magnetic microstructure of cellular composite ferrites will be systematically studied in the aspects of both theoretical and experimental from a micromagnetic perspective. We hope it can further lay the experimental and theoretical foundation for the improvement of magnetic properties of hard magnetic ferrites in our country.

六角晶系M型SrFe12O19硬磁铁氧体由于其良好的化学稳定性和高性价比等特性，目前在很多领域有着广泛的应用。利用软磁/硬磁相之间的交换耦合作用制备交换弹性复合铁氧体是提高硬磁铁氧体磁性能的重要途径。理论研究表明，蜂窝状的硬磁/软磁复合结构是实现交换耦合的最佳途径。但到目前为止，未能在实验中实现这种铁氧体结构，外加缺少微磁学研究的实验和理论支持，极大限制了复合铁氧体磁性能的提升。本项目拟以普通以及磁场诱导的两种不同水热法制备的SrFe12O19为“硬磁性”铁氧体母体相、工艺相近并相对高饱和磁化强度的(Ni,Zn)Fe2O4或CoFe2O4铁氧体等作“软磁相”，利用纳米C球辅助制备蜂窝状复合铁氧体结构，系统研究其磁性能与交换耦合作用的关系，并结合磁力显微学，从微磁角度系统地从实验和理论两方面研究蜂窝状复合铁氧体的微磁结构，以期为我国硬磁铁氧体性能的提高进一步奠定实验和理论基础。

六角晶系M型SrFe12O19(SrM)硬磁铁氧体由于其良好的化学稳定性和高性价比等特性，目前在很多领域有着广泛的应用。利用软磁/硬磁相之间的交换耦合作用制备交换弹性复合铁氧体是提高硬磁铁氧体磁性能的重要途径。理论研究表明，类似蜂窝多孔状的硬磁/软磁复合结构是实现交换耦合的最佳途径。但到目前为止，未能在实验中实现这种铁氧体结构。本项目旨在利用C球制备多孔状的SrFe12O19铁氧体母体，然后在SrM铁氧体的孔洞中引入更高饱和磁化强度Ms的“软磁性相”，制备新型交换弹性复合铁氧体结构，系统研究其磁性能、交换耦合作用和微磁结构。研究表明，利用C球可以成功制备出多孔的SrM铁氧体，并且C球含量对SrM铁氧体的磁性能有着明显的影响；利用软磁性相纳米颗粒的磁性悬浮液可成功制备出具有软、硬磁相之间交换耦合作用的SrM/CoFe2O4复合铁氧体，并在一定程度上可以提高SrM的磁性能。另外，通过研究还发现：1) 成型时的磁场取向对复合铁氧体交换耦合作用的影响并不明显；2) 水热法所得软磁性相ZnFe2O4的磁性来源于制备过程中Zn离子损失所造成的不同离子占位。3) 原材料中Fe源的形貌对SrM铁氧体的结构和磁性能有着较大的影响。利用本项目现有实验数据，发表相关研究论文8篇，其中SCI论文5篇；申请相关国家发明专利5项(已授权3项)；参与相关学术交流16次，培养硕士研究生6人、本科生2人。项目的研究为SrM及其复合铁氧体性能的提高进一步提供了实验和理论支撑。