In this study, to investigate the effect of volume concentration on core loss in the high frequency band (~MHz), easy-plane soft magnetic composites (SMCs) of FeSiAl particles with different volume concentrations were prepared successfully by magnetic field orientation. The permeability of the SMCs was decomposed into the domain wall component and the spin component and was well simulated. The core loss was successfully decomposed into hysteresis loss, eddy current loss and excess loss. It was shown that the permeability of the SMCs was continuously improved as the volume concentration of FeSiAl in the SMCs increased, while the core loss decreased first and then increased due to the different performances of the hysteresis loss, eddy current loss, and excess loss. Samples with a permeability of 310 exhibited the lowest core loss of 399 kW/m3 (f=3 MHz, 10 mT). The results indicated that there is an optimal volume concentration at which SMCs have a relatively high permeability and minimum core loss.
An easy-plane FeSi3.5 composite with excellent magnetic properties and loss properties at MHz were proposed. The easy-plane FeSi3.5 composite has ultra-low loss at 10 MHz and 4 mT, about 372.88 kW/m3. In order to explore the reason that the Pcv of easy-plane FeSi3.5 composite is ultra-low, a none easy-plane FeSi3.5 composite, without easy-plane processing as a control group, measured the microstructure, and the magnetic and loss properties. We first found that the real reason why magnetic materials do not work properly at MHz due to overheat is dramatical increase of the excess loss and the easy-plane composite can greatly re-duce the excess loss by loss measurement and separation. The total loss of none easy-plane FeSi3.5 composite is much higher than that of easy-plane FeSi3.5 composite, where the excess loss is a major part in the total loss and even over 80% in the none easy-plane FeSi3.5 composite. The easy-plane FeSi3.5 composite can greatly reduce the total loss compared to the none easy-plane FeSi3.5 composite, from 2785.8 kW/m3 to 500.42 kW/m3 (3 MHz, 8 mT), with the main reduction being the excess loss, from 2435.2 kW/m3 to 204.93 kW/m3 (3 MHz, 8 mT), reduced by 91.58%. Furthermore, the easy-plane FeSi3.5 composite also has excellent magnetic properties, high permeability and ferromagnetic resonance frequencies. This makes the easy-plane FeSi3.5 composite become an excellent soft magnetic composite and it is possible for magnetic devices to operate properly at higher frequencies, especially at the MHz band and above.
The miniaturization and high frequency of future electromagnetic devices require soft magnetic composites with high permeability, high working frequency and low core loss. In this work, easy-plane amorphous FeSiBCr powders with a thickness of approximately 1~2 μm are obtained by planetary ball milling and successfully fabricated into an arranged soft magnetic composite by using a rotational magnetic field. The complex permeability spectrums of the composite are measured and analyzed. Due to the planar distribution of easy magnetization axes, the amorphous easy-plane FeSiBCr/Si-resin composite shows a permeability of 31 at 1MHz. The core loss of samples is measured from 100 KHz to 5 MHz and discussed in detail. The loss separated results illustrate the eddy current loss and excess loss can be effectively reduced in amorphous easy-plane FeSiBCr/Si-resin composite. These results indicate that, compared with the amorphous none easy-plane FeSiBCr/Si-resin composite, the permeability of the amorphous easy-plane FeSiBCr/Si-resin composite is effectively improved and the core loss is reduced, making it promising for the high-frequency application.
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