| Recently, with the rapid development of wireless communication technology and the widely application of electromagnetic wave, preparing a kind of magnetic material with a larger permeability at GHz band is an important need for high-frequency equipment, anti-electromagnetic interference and electromagnetic absorbers. Several researchers have studied soft magnetic materials with planar anisotropy, and demonstrated that these materials can exceed Snoek’s limit and maintain large permeability in a higher frequency. From this bianisotropy model, high saturation magnetization and high ratio of out-of-plane filed and in-plane anisotropy filed are two key factors for improving the microwave properties of easy-plane materials. Therefore, finding and developing this kind of materials has huge potential and important significant.In this work, we choose rare earth-3d transition metal compounds with high saturation magnetization as a research object and prepared (Ce1-xSmx)2Fe17N3-δ and Y2Fe14-xCoxB particles with easy magnetization plane. Crystal structure, static magnetic properties and high-frequency magnetic properties of these materials have been measured and studied. Lastly, considering the influence of sharp anisotropy, we analyzed their composites’microwave properties with experimental results by the new derived formula. The main results were shown as follows:1. The optimal nitrogenation temperature and duration of preparing (Ce1-xSmx)2Fe17N3-δ particles is 450 ℃ and one hour.2. The value (μ0-1)·f of easy-plane Ce2Fe17N3-δ particles composite can exceed Snoek’s limit, which has a superior microwave property. After Sm substitution, magneto crystalline anisotropic type of (Ce1-xSmx)2Fe17N3-δ (X=0-0.3) shifts: X=0.1 is cone anisotropy and X=0.2,0.3 are uniaxial anisotropies. The microwave magnetic property of easy-cone materials (X=0.1) also can exceed Snoek’s limit.3. The optimal synthesized conditions by ball milling method of Y2Fe14-xCoxB particles is using iron cans and iron bread for 8 hours.4. The value (μ0-1)·f of easy-plane Y2Co14B particles composite can exceed Snoek’s limit, which has a good microwave property. After Fe substitution, magneto crystalline anisotropic type of Y2Fe14-xCoxB(X=6-14) shifts:X=12,13 are plane anisotropies, X= 9,10,11 are cone anisotropies and X=6,7,8 are uniaxial anisotropies. What’s more, initial permeability of these easy-cone materials (X=9,10,11) are all larger than that of easy-plane materials, but their nature resonance frequencies is a little lower. In general, the microwave magnetic properties of easy-cone materials also can exceed Snoek’s limit.5. Considering the influence of sharp anisotropy of the particles, a formula of nature resonance frequency of easy-plane materials is derived by related theories. The formula shows that the reduction of nature resonance frequency of particles composite is attributed to the change in the shape of particles.6. In order to perfect the theory, a formula of the microwave magnetic property for easy-cone materials is also derived. And it shows that the microwave magnetic properties of easy-cone materials also could exceed Snoek’ limit, which are not only related to saturation magnetization and out-of-plane and in-plane anisotropy fields but the direction of easy magnetization. |
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