# Fileset

[MSJ 2024-Sepehri_Final.doc](https://mdr.nims.go.jp/filesets/eba3953c-a513-40a3-9446-e11e2943f5e3/download)

## Creator

[SEPEHRI AMIN Hossein](https://orcid.org/0000-0002-7856-7897), [GAUTAM Ravi](https://orcid.org/0000-0002-5442-6328), S. Hiramoto, [BOLYACHKIN Anton](https://orcid.org/0000-0003-0420-1806), [KULESH Nikita](https://orcid.org/0000-0001-7046-2671), [MAMIYA Hiroaki](https://orcid.org/0000-0002-7840-3008), S. Okamoto, [OHKUBO Tadakatsu](https://orcid.org/0000-0003-3548-1951)

## Rights

[In Copyright](http://rightsstatements.org/vocab/InC/1.0/)

## Other metadata

[Effect of nanostructure on the core loss of soft magnetic materials](https://mdr.nims.go.jp/datasets/db1aed46-9690-4318-a683-13263d185e84)

## Fulltext

MSJ templateEffect of nanostructure on the core loss of soft magnetic materialsH. Sepehri-Amin1, R. Gautam1, S. Hiramoto2, A. Bolyachkin1, N. Kulesh1, H. Mamiya1, S. Okamoto2, T. Ohkubo11National Institute for Materials Science, Tsukuba, Japan2Tohoku University, Sendai, JapanSoft magnets are important components in high-frequency power electronic devices, significantly contributing to efficient energy conversion. They are commonly utilized in transformers, inductors, and magnetic cores within high-frequency power converters. However, cutting-edge power electronics technologies demand soft magnets with minimal core loss at high frequencies. This study demonstrates that high-frequency core losses in Fe-based soft magnetic ribbons can be reduced through nanostructure engineering. We present the optimal microstructure designed to minimize core losses in the 10-20 kHz frequency range.Amorphous Fe-based ribbons with different compositions were prepared by rapid solidification. The amorphous ribbons were annealed at a varied temperature range and time to realize different microstructural features. The microstructure studies were carried out using XRD, TEM, and APT. Magnetic domain observations were conducted by magneto-optical Kerr effect (MOKE) and Lorentz microscopy. Saturation magnetization and coercivity were evaluated by LakeShore VSM 740 vibration sample magnetometer up to an applied magnetic field of 2.0 T. Core losses were measured using B-H analyzer under a magnetic flux density of 1-1.5 T and a frequency range of 0.1-20 kHz.Figure 1(a) shows the total core loss of the Fe-based soft magnetic ribbons obtained under 1.0 T at 10 kHz as a function of the volume fraction of α-Fe crystals of ribbons with different annealing backgrounds. The total core losses at 10 kHz decreased from 165 W/kg in an amorphous state to a value of 75 W/kg as the volume fraction of α-Fe crystals increased to 5.1 vol% in an amorphous matrix, and then increased again as the crystalline volume fraction increased. Detailed analysis of the core losses showed that the contribution of hysteresis and classical eddy current losses to the obtained results is small and the observed core loss dependence on the volume fraction of α-Fe crystals is due to excess losses. According to the microstructure and magnetic domain observation (Fig. 1(b)), it was found that reduction of core loss is due to change in the magnetic domain shape and their movement under an ac magnetic field. Based on detailed microstructural characterizations and magnetic domain observations, the underlying mechanism is discussed. Moreover, we will present how this concept is universal among many different types of soft magnetic materials. In addition, other nanostructural factors which are influential to the core losses of soft magnetic materials will be introduced.Fig. 1. (a) Total core loss measured under 1 T at 10 kHz from Fe-based soft magnetic ribbons as a function of volume fraction of α-Fe crystals, and (b) BF-TEM images, selected area electron diffraction patterns, and magnetic domain configuration in the remanence state obtained from samples i and ii marked in (b).－2－