Provided by Hideto Yanagihara

Researchers at University of Tsukuba have developed a magnetic measurement system capable of precisely capturing the full magnetization hysteresis (M-H) loop of magnetic materials up to saturation at megahertz frequencies and under high magnetic fields of up to 0.5 tesla. This advancement allows direct evaluation of magnetization processes under large-amplitude and high-frequency conditions, which have historically been difficult to investigate due to the limitations of existing measurement techniques.

Tsukuba, Japan—High-frequency magnetic characteristics are essential for improving the efficiency, miniaturization, and operating frequency of power conversion devices such as power supply circuits, inductors, and transformers. However, conventional measurement methods face two major challenges. First, generating sufficiently large magnetic fields at high frequencies requires high power and high voltages. Second, many methods can probe only the initial magnetization region because the achievable magnetic field amplitude is limited. Consequently, reproducing the actual operating environment of next-generation power electronics devices has remained difficult.

In this study, the research team developed a magnetic measurement system capable of accurately measuring the complete M-H loop, including the irreversible magnetization process, up to saturation, even under high-frequency (MHz-band) and high-field (up to 0.5 T) conditions. The system employs a low-impedance LC-resonant excitation coil that can stably generate large-amplitude alternating magnetic fields in the megahertz range. This design enables quantitative and highly reproducible magnetization measurements that were previously unattainable.

Using a commercial Ni-Zn ferrite sample, the researchers successfully obtained a complete M-H loop up to saturation at 1.2 MHz. This result demonstrates that the new system can quantitatively capture the dynamic magnetization behavior of magnetic materials under both high-frequency and large-amplitude magnetic field conditions. These parameters closely match real device operation but were previously difficult to evaluate using conventional techniques. The measurement technique is expected to serve as a foundational tool for advancing next-generation power electronics and to support the design of improved magnetic materials as well as the development of more efficient, compact, and higher-frequency electronic devices.

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This work was supported by Japan Science and Technology Agency, Adaptable and Seamless Technology transfer Program through target driven R&D (Grant number AS2915014R). This work was partly supported by JST SPRING, Grant Number JPMJSP2124.

Original Paper

Title of original paper:

A Magnetometer for Dynamic Full M-H Loop Measurements in the Megahertz Range

Journal:

IEEE Transactions on Instrumentation and Measurement

DOI:

10.1109/TIM.2026.3659653

Correspondence

Professor YANAGIHARA Hideto
Institute of Pure and Applied Sciences, University of Tsukuba

Related Link

Institute of Pure and Applied Sciences