Materials, physics, and systems for multicaloric cooling

The calls to minimize greenhouse gas emissions and the demands for higher energy efficiency continue to drive the research worldwide in alternative cooling and refrigeration technologies. The field of caloric cooling has undergone a series of transformations in the past several decades bolstered by the advent of new materials and devices, and these developments have helped fuel the advent of multicalorics in the past decade. Multicaloric materials systems inherently display one or more types of ferroic orders that can give rise to multiple field-induced phase transitions responsible for the caloric effects. Just as multiferroic materials possessing co-existing order parameters have unveiled a plethora of physical phenomena and applications over the years, multicaloric cooling materials have the potential to open up entirely new avenues for extracting heat and spearhead hitherto unknown technological applications. In this Perspective, we survey the emerging field of multicaloric cooling and explore the state-of-the-art caloric materials systems responsive to multiple fields. We present our visions of future applications of multicaloric and caloric cooling in general including key factors governing the overall system efficiency of the cooling devices.