Influence of heat-treatment on structure and magnetic properties of 10 <i>μ</i> m-thick Fe-1,2,3 wt. %Si foils

The influence of annealing temperature on the structure and magnetic properties of 10 μm-thick Fe-1, 2, and 3 wt. %Si foils was investigated. The coercivity of each foil decreased and its relative permeability increased as the annealing temperature increased, meaning the improvement of soft magnetic properties of these foils. The core loss of each foil at 100 kHz under a maximum magnetic flux density of 500 mT showed a decrease intendency with the increase of annealing temperature, owing to the suppression of the hysteresis loss by grain growth after annealing. Furthermore, from the loss separation of each foil, it was found that the eddy current loss slightly decreased and excess loss tend to increase with the increase of annealing temperature regardless of Si content. Therefore, these results suggest that an appropriate annealing temperature can improve the magnetic properties and core loss of ultra-thin Fe–Si foils, making them applicable as magnetic materials for next generation passive components in the frequency range up to several hundreds kHz.