|Alternative Title||Microwave magnetic properties of rare earth intermetallic powder with easy-plane anisotropy
|Place of Conferral||兰州
|Other Abstract||High frequency permeability of magnetic materials is becoming more and more important in nowadays national defense industry. It's because the performance of magnetic devices operating at high frequency strongly depends on the permeability dispersion behaviors, such as cellular phones, common-mode choke coils and corresponding electromagnetic (EM) wave absorbers. Especially, the EM wave absorption properties in S-band (2-4 GHz). For example, Wi-Fi network at 2.4 GHz, microwave ovens at 2.45 GHz, and fixed satellite at 2.4, 2.6 GHz. According to current EM wave theories, the permeability (μr) of materials should be improved to obtain a smaller matching thickness (tm) in a lower S-band frequency. Generally, the capability of traditional high frequency magnetic materials with uniaxial anisotropy can be well discribed by Snoek's theory, the product of the initial permeability and resonance frequency is proportional to the saturation magnetization, which therefore significantly limits the application of materials. However, in recent years, the planar ferrites, especially planar anisotropy soft magnetic thin films and planar anisotropy flake-shaped particles, have shown higher resonance frequency and higher permeability at higher frequencies than that of the bulk materials and most spherical particle composites. The high frequency magnetic properties then can be improved by changing out-of-plane and in-plane magnetocrystalline anisotropies.
According to the theory above, the Y2Fe17, Y2Fe17Nx and Y2Fe17-xCox particles have been prepared and the magnetocrystalline anisotropy properties were also studied using different methods. At last, we discussed the high frequency magnetic properties of Y2Fe17, Y2Fe17Nx and Y2Fe17-xCox paraffin compounds. The main results are obtained as follows:
Y2Fe17 magnetic powders
The intensity of the  diffraction is strongly enhanced when XRD measurement is performed on the oriented composite surface perpendicular to the cylindrical axis proved that the Y2Fe17 are planar anisotropy magnetic structures in atmosphere temperature;
The Snoek value is 4.6 GHz for the Y2Fe17 composite with 30 vol %, where the Ms is the saturation magnetization of Y2Fe17 powders. However, for planar anisotropy Y2Fe17 powders, the value of the permeability is related to the out of plane anisotropy-field Ha and in plane anisotropy-field Hp, it is observably found that the product of the initial permeability and the nature resonance is larger than the ...|
池啸. 易面各向异性稀土金属间化合物磁粉的微波磁性研究[D]. 兰州. 兰州大学,2013.
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