稀土永磁纳米颗粒及纳米片磁性能的尺寸效应及磁硬化机理

本项目以稀土永磁纳米颗粒及纳米片的成分、结构和磁性为研究对象。首先采用表面活性剂辅助球磨和颗粒分级技术制备出颗粒尺寸可调控的窄粒度分布稀土永磁纳米颗粒及纳米片。在此基础上，观察分析材料的化学成分、晶体结构、显微组织及磁畴结构，测定其饱和磁化强度、磁晶各向异性、磁有序转变温度等内禀磁参量和剩磁、矫顽力、磁能积等外禀磁参量；并以微磁学有限元的方法建立与纳米颗粒及纳米片结构特征相符的理论模型。进一步，深入研究材料的成分、结构对其磁性能的影响。其中重点考查各类稀土永磁材料的磁畴结构和磁性能随其尺寸的变化规律；并考查材料磁化、反磁化过程中磁畴演化行为及其在反磁化过程中形成磁硬化的详细机制。最终探明稀土永磁纳米颗粒及纳米片的微结构与磁性能之间的构效关系，建立材料磁硬化的理论模型。本研究的结果有望形成一批纳米结构稀土永磁材料的磁性参量基础数据，同时为研制具有优异永磁特性的新型稀土永磁材料提供科学指导。

In present project, the chemical composition, structure, and magnetic properties will be studied for rare-earth containing permanent magnetic nanoparticles and nanoflakes prepared by surfactant assisted ball milling and subsequent size selection process. Firstly, size controllable nanoparticles and nanoflakes with narrow size distribution will be produced. Secondly, the chemical composition, crystal structure, microstructure, and magnetic domain of the nanoparticles and the nanoflakes will be examined, and intrinsic magnetic properties such as magnetization saturation, magneto-crystalline anisotropy, magnetic transition temperature as well as extrinsic magnetic properties such as remanence, coercivity, and maximum energy product of the materials will be measured; a more realistic model for the nanoparticles and the nanoflakes will be set up by using the micromagnetic finite element method. Thirdly, the magnetic domain structure and magnetic properties of the nanoparticles and the nanoflakes as a funtion of their size will be studied, and domain structure evolution during magnetization and demagnetization processes as well as magnetic hardening mechanism of both the nanoparticles and the nanoflakes will be investigated. Finally, correlation between microstructure and magnetic properties of the rare-earth containing permanent magnetic nanoparticles and nanoflakes will be clarified, and theoretical model of magnetic hardening mechnism of the materials will be set up. As a result, a batch of basic magnetic properties data for nanostructured rare-earth containing permanent magnetic materials will be provided, and scientific instruction for fabricating novel rare-earth containing magnetic materials with excellent permanent magnetic properties will be proposed.