A research team from the Tokyo University of Science (TUS) and the National Institute of Advanced Industrial Science and Technology (AIST) has developed a groundbreaking measurement system that reveals how energy is lost in soft magnetic materials. The discovery could accelerate the design of next-generation power electronics, making transformers, motors, and renewable energy systems smaller, lighter, and more efficient.

Cracking the Puzzle of Iron Loss

Soft magnetic materials are essential to devices such as transformers and generators, but their efficiency is fundamentally limited by iron loss, where energy is wasted as heat under changing magnetic fields. At high frequencies, the most significant contributor is excess eddy current loss, caused by irregular movements of magnetic domain walls (boundaries between magnetic regions). Despite its importance, the physical origin of this loss has remained unclear.

Magnetic Barkhausen noise (MBN) — tiny signals produced by domain wall movements — provides a window into these dynamics. However, existing systems lack the sensitivity and bandwidth to capture individual MBN events with enough clarity.

A New Wide-Band, High-Sensitivity System

Led by Assistant Professor Takahiro Yamazaki of TUS, the team created a wide-band, high-sensitivity MBN measurement system featuring a dual-layer coil jig, full electromagnetic shielding, and a custom low-noise amplifier. This setup enabled single-shot, high-fidelity detection of individual MBN pulses in Fe–Si–B–P–Cu (NANOMET®) ribbons.

“Our guiding principle was to measure what was previously unmeasurable,” said Dr. Yamazaki. “We succeeded in directly observing domain wall relaxation in metallic ribbons for the first time.”

Key Findings

• Direct evidence of domain wall relaxation: The system revealed isolated MBN pulses with a relaxation time of ~3.8 μs — much shorter than conventional models predicted.
• New physical model: The team showed that excess eddy current loss stems primarily from eddy current damping during domain wall motion, not intrinsic magnetic viscosity.
• Path to material design: Heat-treated NANOMET® ribbons displayed smoother domain wall motion, reducing MBN pulse amplitudes and pointing to ways to cut energy loss through microstructural control.
  

Toward Greener Power Electronics

By clarifying the physical origin of excess eddy current losses, the study provides a roadmap for engineering ultra-efficient soft magnetic materials. Potential applications include high-frequency transformers, electric vehicle motors, and renewable energy systems.

“Our method opens up broad possibilities for designing low-loss magnetic materials,” said Dr. Yamazaki. “The insights will help create devices with higher efficiency, improved driving performance, and lower power consumption.”

Original Publication
Authors: Takahiro Yamazaki, Shingo Tamaru and Masato Kotsugi.
Journal: IEEE Access
DOI: 10.1109/ACCESS.2025.3596507
Method of Research: Experimental study
Subject of Research: Not applicable
Article Title: Analysis of Magnetic Barkhausen Noise to Reveal Domain Wall Dynamics in Amorphous/Nanocrystalline Ribbons
Article Publication Date: 7-Aug-2025
COI Statement: The authors declare that they have no conflicts of interest.

Original Source: https://www.tus.ac.jp/en/mediarelations/archive/20250903_6874.html