Evolution of magnetic domain structure and magnetic properties of Fe-based nanocrystalline powder cores during transverse magnetic field annealing

In this work, transverse magnetic field annealing (TA) was performed to FeSiBNbCu nanocrystalline powder cores (NPCs), and the magnetic properties, microstructure, and magnetic domain structure were in detail studied comparing with those after normal annealing (NA), and the mechanism of the improvement of soft magnetic properties by TA was elucidated. The experimental results show that the core loss of the sample is reduced by 14 % and the coercivity is reduced by 38 % after TA at 450 °C compared to the NA sample. The direct current bias performance of the TA sample is maintained at 67 % under a 100 Oe bias field. TA optimizes the soft magnetic properties of NPCs by optimizing the domain structure, reducing the formation of micro-vortex dots and broadening the size of the domain. These results can provide a good guide for optimizing the performance of NPCs with low core loss at high frequency.