(Magneto)caloric refrigeration: Is there light at the end of the tunnel?

Abstract

Caloric cooling and heat pumping rely on reversible thermal effects triggered in solids by magnetic, electric or stress fields. In the recent past, there have been several successful demonstrations of using firstorder phase transition materials in laboratory cooling devices based on both the giant magnetocaloric and elastocaloric effects. All such materials exhibit non-equilibrium behaviours when driven through phase transformations by corresponding fields. Common wisdom is that non-equilibrium states should be avoided; yet, as we show using a model material exhibiting a giant magnetocaloric effect, nonequilibrium phase-separated states offer a unique opportunity to achieve uncommonly large caloric effects by very small perturbations of the driving field(s). This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.