A Study on an Easy-Plane FeSi(3.5) Composite with High Permeability and Ultra-Low Loss at the MHz Frequency Band

An easy-plane FeSi(3.5) composite with excellent magnetic properties and loss properties at MHz were proposed. The easy-plane FeSi(3.5) composite has ultra-low loss at 10 MHz and 4 mT, about 372.88 kW/m(3). In order to explore the reason that the [Formula: see text] of easy-plane FeSi(3.5) composite is ultra-low, a none easy-plane FeSi(3.5) 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 FeSi(3.5) composite is much higher than that of easy-plane FeSi(3.5) composite, where the excess loss is a major part in the total loss and even over 80% in the none easy-plane FeSi(3.5) composite. The easy-plane FeSi(3.5) composite can greatly reduce the total loss compared to the none easy-plane FeSi(3.5) composite, from 2785.8 kW/m(3) to 500.42 kW/m(3) (3 MHz, 8 mT), with the main reduction being the excess loss, from 2435.2 kW/m(3) to 204.93 kW/m(3) (3 MHz, 8 mT), reduced by 91.58%. Furthermore, the easy-plane FeSi(3.5) composite also has excellent magnetic properties, high permeability and ferromagnetic resonance frequencies. This makes the easy-plane FeSi(3.5) 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.