Heat recycling with magnetocaloric and thermomagnetic materials for sustainable energy conversion

Solid-state magnetocaloric effect (MCE) and thermomagnetic effect (TME) under external magnetic stimuli can be effectively employed for designing new sustainable energy conversion techniques, where MCE exploits field-driven temperature shifts for solid-state cooling/heating and TME harnesses temperature-dependent magnetization changes to convert thermal gradients into electricity. In this chapter, we examine the magnetocaloric and thermomagnetic materials for sustainable heat recycling applications, and summarize the corresponding representative materials, as well as important progress in recent years, structured along a foundational working mechanism-promising materials-applications-deep understanding framework. Specifically, we highlight some key understandings of the MCE/TME by utilizing state-of-the-art technical tools such as synchrotron X-ray, neutron scattering, muon spin spectroscopy, positron annihilation spectroscopy, high magnetic pulse fields, etc. and highlight their importance towards advanced materials design and development. The multimodal characterization, leveraging advanced large-scale facilities, has deepened insights into microstructural changes and phase transition dynamics, which are critical for performance optimization. Finally, despite challenges, the opportunities and perspectives on further developments are discussed. Further in-depth understanding and manufacturing technology advancement combined with fast-developed artificial intelligence and machine learning are expected to advance the magnetocaloric and thermomagnetic energy conversion technology closer to real applications, and the synergies will accelerate the deployment of these technologies for carbon-neutral heat recycling. © 2025 Published by Elsevier B.V.