纳米硬/软磁复合永磁薄膜磁滞回线的微磁学理论综述

Review of Micromagnetic Theory for Hysteresis Loop of Nanocomposite Hard / Soft Permanent Magnets

纳米硬/软磁交换弹簧复合材料是一种新型的高性能永磁体材料,在基础研究和实际应用2个方面都得到广泛的重视.它有着丰富的磁学性质,特别是在磁能积方面潜力巨大,理论磁能积密度高达1 MJ/m3.微磁学是量子磁学和宏观磁性的桥梁,是研究材料磁滞回线和宏观磁性的重要理论,它能清晰地阐述材料的磁化反转机制,预测磁滞回线和磁性能.以薄膜结构为例,综述3种重要的计算复合磁体磁滞回线的微磁学方法:一维全解析模型;一维半解析模型;三维数值计算模型,并分别讨论3种方法的优点与不足.将不同方法得到的计算结果进行比较,重点分析硬/软磁相厚度和易磁化轴取向对复合磁体宏观磁滞回线以及矫顽力机制的影响,并与实验进行比较,讨论理论和实验产生差别的原因,提出一些提高材料磁性能特别是矫顽力和磁能积的的方法.

Exchange-spring nanocomposite hard / soft magnets,as a new type of high-performance permanent magnets,has fundamental researches and applications and attracte much attention. This new kind of magnets with numerous magnetic properties and a giant especial magnetic energy product＇has a theoretical upper limit of 1 MJ / m3. Micromagnetics as a bridge between the quantum magnetism and macroscopic magnetism,is an important theory to investigate the properties of magnetic materials and can clearly demonstrate the reversal mechanism of a given material as well as predicting its hysteresis loop and magnetic properties. This paper mainly expounds the hysteresis loops of thin film composite magnets according to three important micromagnetic calculation models： full analytical,quasi-analytical and numerical models. The advantages and weaknesses of each model are discussed. The results obtained from the three different models are compared and the effect of the hard / soft phase thicknesses and easy axis orientation on the macro hysteresis loops and coercivity mechanism are analysed. The gap between the theoretical and the experimental values are disscussed to propose some methods to enhance the magnetic properties of a given material,especially its coercivity and energy product.