Soft magnetic properties of nano-SiO2 coated FeNi alloy powder at high frequencies

Soft magnetic composites serve in electrical applications and sustainable energy supply, the magnetic flux changes in response to changes of the applied magnetic field, with energy loss. To reduce the loss, in this paper, the soft magnetic composite Fe 50 Ni 50 powder coated with nano-SiO 2 was prepared by tetraethoxysilane sol–gel method, and the microstructure of the coating was characterized. Then, soft magnetic Fe 50 Ni 50 powder cores have been prepared, and annealed with different atmospheres. The power loss is lower when the magnetic cores were annealed in a reducing hydrogen atmosphere. The lowest power loss (1390.7 mW/cm 3 , f  = 1000 kHz, B  = 50 mT, 120 °C) was obtained when the cores annealed at 730 °C in H 2 atmosphere. The results show that the eddy current loss is significantly reduced by coating SiO 2 , and the power loss is reduced about 33% in high-frequency (1 MHz and 50 mT, 25 °C). From 25 to 120 °C, the power loss at 1 MHz decreases by about 33% due to the reduction of hysteresis loss and eddy current loss. The excellent properties are very applicable for the inductors of 5G technology.