Lowering iron loss in EV motors: new model maps how maze-like magnetic domains reverse in soft magnets

Researchers at Tokyo University of Science have created an advanced computational model that maps the reversal of magnetisation within complex “maze domain” structures found in soft magnetic materials. These materials, commonly used in electric motor cores, feature intricate magnetic domains that change direction in response to alternating magnetic fields—a process that contributes significantly to iron loss and energy dissipation in motors. The new model aims to deepen understanding of these microscopic behaviours, which have traditionally been challenging to predict due to their abrupt and temperature-dependent nature. The model, named eX-GL (entropy-feature-eXtended Ginzburg-Landau), integrates persistent homology—a sophisticated mathematical technique for analysing topological features—with machine learning and physics-based free energy calculations. By applying this hybrid approach to microscopic images of rare-earth iron garnet samples at varying temperatures, the researchers identified four principal energy barriers that govern the magnetisation reversal in maze domains. The findings reveal how exchange interactions, demagnetising effects, and entropy collectively influence the complex dynamics of domain wall evolution. One of the key insights from the study is the role of entropy and exchange energy coupling in the growth and complexity of maze domains as domain walls lengthen. This interplay drives the intricate zigzag patterns that characterise these magnetic structures, which in turn directly affect hysteresis loss—a major factor in motor efficiency. By elucidating these mechanisms, the model provides a new framework for predicting and potentially mitigating iron losses in electric motors. The implications of this research are significant for the development of more efficient electric motors, particularly in the context of electric vehicles where reducing energy loss is critical. Understanding the microscopic magnetic behaviour could lead to improved material design and motor core engineering, ultimately enhancing performance and sustainability. The study, published in Scientific Reports in February 2026, marks a promising advance in the quest to optimise electric motor technology through fundamental materials science.