Multicaloric and coupled-caloric effects**Project supported by the National Key Research and Development Program of China (Grant Nos. 2017YFB0702702, 2019YFA0704904, 2018YFA0305704, 2017YFA0206300, 2017YFA0303601, and 2016YFB0700903), the National Natural Science Foundation of China (Grant Nos. U1832219, 51531008, 51771223, 51590880, 51971240, 11674378, 11934016, and 11921004), and the Key Program and Strategic Priority Research Program (B) of the Chinese Academy of Sciences.

Abstract

The multicaloric effect refers to the thermal response of a solid material driven by simultaneous or sequential application of more than one type of external field. For practical applications, the multicaloric effect is a potentially interesting strategy to improve the efficiency of refrigeration devices. Here, the state of the art in multi-field driven multicaloric effect is reviewed. The phenomenology and fundamental thermodynamics of the multicaloric effect are well established. A number of theoretical and experimental research approaches are covered. At present, the theoretical understanding of the multicaloric effect is thorough. However, due to the limitation of the current experimental technology, the experimental approach is still in progress. All these researches indicated that the thermal response and effective reversibility of multiferroic materials can be improved through multicaloric cycles to overcome the inherent limitations of the physical mechanisms behind single-field-induced caloric effects. Finally, the viewpoint of further developments is presented.