Analysis of Magnetic Barkhausen Noise to Reveal Domain Wall Dynamics in Amorphous/Nanocrystalline Ribbons

Understanding and minimizing iron loss in soft magnetic materials is essential for the development of high-efficiency next-generation power electronics systems. Excess eddy current loss, which arises from localized eddy currents induced by moving domain walls (DWs), constitutes a major fraction of the total iron loss at high frequencies. However, the detailed physical mechanisms underlying excess eddy current loss remain unclear, primarily due to the lack of suitable experimental and analytical techniques. In this study, a wide-band and high-sensitivity magnetic Barkhausen noise (MBN) measurement system was developed to investigate DW dynamics in $25~\mu $ m-thick amorphous/nanocrystalline Fe–Si–B–P–Cu (NANOMET)® ribbons. This system enabled high-fidelity and single-shot capture of individual MBN pulses, which provided direct experimental evidence of DW relaxation in metallic ribbons. In the non-annealed amorphous state, isolated MBN pulses with steep leading edges and exponentially decaying trailing edges were clearly observed. Statistical analysis of these events yielded a mean relaxation time of $3.8~\mu $ s with a standard deviation of $1.8~\mu $ s. Analytical modelling suggests that eddy current damping exceeds intrinsic DW damping in the relaxation process. These findings advance the understanding of excess eddy current loss mechanism and thereby contribute to the microstructural design of low-loss soft magnetic materials.