Characterization of caloric effects for magnetostructural transition materials: State-of-the-art and prospects

Due to its environmental friendliness and high theoretical energy conversion efficiency, solid-state refrigeration based on caloric effects of magnetostructural transition (MST) materials driven by external stimuli is deemed as the most promising technology to replace the current vapor compression refrigeration. To accurately and efficiently characterize caloric effects for a MST is one of the keys to solid-state refrigeration. The research of caloric effects for MSTs and associated solid-state refrigeration relies to a large extent on characterization techniques. Regular methods, for instance, thermocouple and calorimetry, are not capable of characterizing caloric effects of MSTs under external field(s) and of understanding the mechanism of magnetostructural coupling in these materials. Therefore, new methods are being introduced and new experimental setups are being built as the research deepens. In recent years, beyond single-index and macroscopic-parameter assessment, characterization of caloric effects is not only going deeply with multi-index measurement, in-situ methods, and microscopic techniques, but is being combined with new approaches including high-throughput methods and machine learning methods. Herein, we review the state-of-the-art and prospects of characterization of caloric effects for MSTs including basic principles, magnetocaloric effect, elastocaloric effect, barocaloric effect and multicaloric effect.