Elasto-Magnetocaloric Effect
Refrigeration based on the magnetocaloric effect promises high efficiency and zero emis-sion of global warming gases. However, magnetic refrigeration is inherently expensive be-cause the refridgerent must experience a large change of applied magnetic field (>1.5 T) to achieve any useful cooling. High costs will arise from the high field requirement, which can only be efficiently obtained using expensive rare earth permanent magnets. This lack of cost-effectiveness is the major obstacle limiting magnetocaloric refrigeration from wide industrial and commercial applications. Despite active research efforts, new magneto-caloric materials that require less magnetic field have not yet been reported. Here, we show that cost concerns can be mitigated via a new energy pathway predicted by the thermody-namic phenomenon termed the elasto-magnetoclaoric effect: It is known that the transfor-mation temperatures of first order martensitic phase transformations and second order magnetic transformations can be shifted by elastic and magnetic fields, respectively. In ferromagnetic shape memory alloys these order parameters are coupled. We realized that this coupling will enable us to mechanically induce both transformations simultaneously, thereby attaining a large change in the magnetic entropy that otherwise requires a large magnetic field. In addition the release of latent heat, which the material will absorb once the stress is removed, would provide a welcome enhancement of the cooling capacity.