Abstract: Minimizing core loss of soft magnetic amorphous alloys is of crucial importance for developing high-efficiency electrical and electronic devices. Despite the complex and diverse physical origins of the loss characteristics at different frequencies, reducing the coercivity has long been regarded as one of the main approaches to reducing core losses. Here, we report a new approach to control core loss in soft magnetic amorphous alloys, achieving an exceptional reduction of up to 65 % in high-frequency losses of a commercial Fe₇₈Si₉B₁₃ alloy, even when the coercivity is increased approximately threefold beyond its optimal value. This phenomenon is attributed to local structural ordering caused by over-annealing, which forms a unique mechanism dominated by the nucleation and growth of reversed magnetic domains. Hence, the excess core loss primarily resulting from local eddy currents around the moving domain walls is significantly reduced, leading to remarkably low high-frequency core loss. Through a systematic study on the variation of core loss, a two-stage model based on stress release and local structural ordering is proposed to elucidate the mechanism of annealing-induced core loss modulation. These findings provide a groundbreaking and practical strategy for the core loss control of soft magnetic amorphous alloys and pave the way for their enhanced performance in high-frequency applications.

Key words: Fe-based amorphous alloy, High-frequency core loss, Magnetization mechanism, Local structural ordering, Stress Release, Over-annealing