Energy-efficient and environment-friendly elastocaloric refrigeration, which is a promising replacement of the conventional vapor-compression refrigeration, requires extraordinary elastocaloric properties. Hitherto the largest elastocaloric effect is obtained in small-size films and wires of the prototype NiTi system. Here, we report a colossal elastocaloric effect, well exceeding that of NiTi alloys, in a class of bulk polycrystalline NiMn-based materials designed with the criterion of simultaneously having large volume change across phase transition and good mechanical properties. The reversible adiabatic temperature change reaches a strikingly high value of 31.5 K and the isothermal entropy change is as large as $45\mathrm{J}{\mathrm{kg}}^{-1}{\mathrm{K}}^{-1}$. The achievement of such a colossal elastocaloric effect in bulk polycrystalline materials should push a significant step forward towards large-scale elastocaloric refrigeration applications. Moreover, our design strategy may inspire the discovery of giant caloric effects in a broad range of ferroelastic materials.

We report a giant effective magnetic refrigeration capacity in a Ni₄₀Co₁₀Mn₄₀Sn₁₀ multifunctional alloy. With a large magnetization difference between austenite and martensite, this alloy shows a strong magnetic field dependence of transformation temperatures. Complete magnetic-field-induced structural transformation and a considerable magnetic entropy change are observed in a broad operating temperature window of 33 K near room temperature. Consequently, an effective magnetic refrigeration capacity of 251 J/kg for 5 T is achieved, which is the largest value for Ni-Mn-based Heusler alloys and comparable to that of the high-performance Gd-Si-Ge and La-Fe-Si magnetocaloric materials. Incorporating the advantages of low cost and non-toxicity, this alloy shows very promising prospects for room-temperature magnetic refrigeration.