沿固定晶面断裂的强磁晶各向异性R2Co17(R=Y,Pr,Co)片状软磁微粉GHz频段的磁性

With the increase of information transmission speed and working frequency of electron devices, the magnetic powder working above GHz even 10GHz while possessing high permeability has immense application potential, such as new-type inductance, microwave communication, civil absorber, and military stealth coating. In our accomplished project, we have theoretically demonstrated that the easy-plane soft magnetic micro-particles with strong magnetocrystalline anisotropy can satisfy the above requirement. In our previous project, the microwave magnetic properties of easy-plane R-3d intermetallic compound with irregular shape have been investigated. In this project, we explore and study the flake-shaped R-3d intermetallic compound flakes which are broken from the easy magnetization plane. This structure can dramatically increase the microwave permeability by decreasing the demagnetization field effect when the microwave magnetic field drives the magnetic moment, and increase the cut-off frequency through increasing the total out-of-plane anisotropy field by inducing the demagnetization field. The product of initial susceptibility and cut-off frequency for the flake-shaped R-3d intermetallic compound particles will increase remarkably compared to the particles with irregular shape, and can be more than 25 times as large as Snoek limit. For a composite filled by the particles in this project, the initial permeability can exceed 5.0 while the cut-off frequency is above 10 GHz.

随着信息传输速度和电子器件工作频率的提高，工作在GHz甚至10GHz以上频段的高性能磁粉在新型电感器件、微波通信、民用电磁波吸收体及军用雷达波隐身涂层有巨大应用需求。在已结题的项目中，我们已从物理机理上阐明：强磁晶各向异性的易面型稀土-3d金属间化合物软磁微粉在满足上述需求上有内在潜能。本课题在已经研究的不规则形貌稀土-3d金属间化合物软磁微粉基础上，着力制备沿晶体中的c面（易磁化面）定向断裂的片状微粉，使磁矩不仅躺在晶体的易磁化面内，而且躺在片的面内。该结构微粉不但能有效降低微波磁场驱动磁矩进动时的退磁场效应，显著提升磁导率；还能利用磁晶各向异性场和退磁场的叠加来增强总的面外各向异性场，进一步提高截止频率；该微粉的起始磁化率和截止频率的乘积有望超出传统Snoek极限25倍以上，其复合材料（Vc=0.35）的截止频率在10GHz以上的同时，起始磁导率可达到5.0以上。

本项目利用表面活性剂高能球磨技术，实际制作了Nd2Co17,Y2Co17,Pr2Co17片状颗粒，片的厚度在亚微米，取向样品的XRD结果显示三种样品均沿着c晶面断裂。测试了三种式样复合物的电磁参数，复合物均展现出了高的自然共振频率和高的起始磁导率，特别是Nd2Co17和Pr2Co17复合物样品，其自然共振频率达到10GHz以上，这是迄今为止发现的自然共振频率最高的软磁复合材料。实际应用方面，磁粉经表面氧化处理降低介电常数，复合物在X波段展现出优异的吸波性能。该研究从理论和实验上阐明了制作GHz乃至10GHz软磁材料的方法，对于开发GHz频段的高磁导率软磁材料有重要借鉴和指导价值。