Research Digest 11Advanced microscopy in combination with state-of-the-art data processing provided the basis for realistic micromagnetic models capable of replicating magnetic materials in nanometer scale details. This was the way to minimize the burden of assumptions in revealing correlations between microstructural features and hysteretic properties. There were several illustrative cases Fig. 1. Micromagnetic models of (a) FePt nanogranular media [1,2] and (b) SmFe12-based thin films [3] developed based on TEM images. These models are able to reproduce well experimental magnetic properties such as the hysteresis loop. (c) More advanced case of developing a bulk model based on FIB-SEM tomographic data acquired for a hot-deformed Nd-Fe-B magnet.released in 2022 [1-3]. First, a TEM image-based micromagnetic model of FePt nanogranular media (Fig. 1a) [1] allowed to elucidate the effect of defects, such as {111} twins, on magnetic properties and to realize the machine learning (ML) assisted approximation of experimental hysteresis loops [2]. Second, the similar approach was used to explain the suppressed coercivity in SmFe12-based anisotropic thin films (Fig. 1b) and to guide toward its remarkable enhancement [3]. As the next step, a new approach for constructing a large-scale micromagnetic model based on the FIB-SEM tomography was proposed and is going to be applied to Nd-Fe-B hot-deformed magnets (Fig. 1c). One more example of incorporating ML was research on the Fe2P-type magnetocaloric material which composition was successfully tuned to reduce the transition temperature below 77 K preserving relatively high magnetocaloric performance [4].References 1) A. Bolyachkin et al., Acta Mater. 227, 117744 (2022). 2) E. Dengina, et al., Scripta Mater. 218, 114797 (2022). 3) A. Bolyachkin et al., Acta Mater. 227, 117716 (2022). 4) J. Lai, et al., Acta Mater. 232, 117942 (2022).1. Outline of ResearchThe development of environmental benign technologies with zero CO2 emission and deep integration of information technologies into daily life are the main trends for Japan toward the Society 5.0. Magnetic materials play one of the major roles in this process, for example, high-performance permanent magnets and magnetocaloric materials are essential for green energy conversion, while hard disk drives are the most reasonable choice for storing big data. To realize such a societal transformation, the performance of magnetic materials should be improved closer to their physical limits that can be accelerated by advanced computer simulations and data science.2. Research ActivitiesData Driven Development of Magnetic MaterialsAnton BOLYACHKIN
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