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Magnetic shape memory alloys (MSMAs) have attracted great interests due to their multifunctional properties associated with external-field-induced martensitic transition, such as magnetostrain, magnetoresistance, magnetocaloric effect and elastocaloric effect. Search for MSMAs displaying a unique combination of strong metamagnetic transition and stable, large caloric effect is nowadays very active. Here we report the simultaneous achievement of a strong metamagnetic transition as well as a large magnetic-field-induced entropy change of 17.4 J kg−1 K−1 under 2 T and a stable, large elastocaloric effect with adiabatic temperature change of ∼5.0 K during more than 2100 mechanical cycles, in a Ni-Fe-Co-Mn-Sn MSMA. Such combination in a single material has never been reported in the literature. Furthermore, we demonstrate that fully reversible metamagnetic transition and consequently large, reversible multicaloric effect can be achieved by increasing magnetic field from 0 T to 2 T at zero stress and decreasing field from 2 T to 0 T at a uniaxial stress of 23.5 MPa. This dual-stimulus magnetic-mechanical multicaloric cooling cycle also provides an opportunity for achieving reversible magnetoresistance and magnetostrain under the coupling of a low magnetic field and small stress, which is beneficial for practical applications. The high cyclic stability of large caloric effects is ascribed to the good geometric compatibility at the interface between austenite and martensite as revealed by employing multiscale characterization approaches, including in-situ synchrotron high-energy X-ray diffraction and transmission electron microscopy. This study has great implications on developing high-performance multifunctional alloys with magnetostructural transition for actuation, magnetic recording and solid-state refrigeration applications. Image 1 [ABSTRACT FROM AUTHOR]

Novel multicaloric cooling utilizing the giant caloric response of Ni-Mn-based metamagnetic shape-memory alloys to different external stimuli such as magnetic field, uniaxial stress and hydrostatic pressure is a promising candidate for energy-efficient and environmentally-friendly refrigeration. However, the role of microstructure when several external fields are applied simultaneously or sequentially has been scarcely discussed in literature. Here, we synthesized ternary Ni-Mn-In alloys by suction casting and arc melting and analyzed the microstructural influence on the response to magnetic fields and uniaxial stress. By combining SEM-EBSD and stress-strain data, a significant effect of texture on the stress-induced martensitic transformation is revealed. It is shown that a <001> texture can strongly reduce the critical transformation stresses. The effect of grain size on the material failure is demonstrated and its influence on the magnetic-field-induced transformation dynamics is investigated. Temperature-stress and temperature-magnetic field phase diagrams are established and single caloric performances are characterized in terms of Δs T and ΔT ad. The cyclic ΔT ad values are compared to the ones achieved in the multicaloric exploiting-hysteresis cycle. It turns out that a suction-cast microstructure and the combination of both stimuli enables outstanding caloric effects in moderate external fields which can significantly exceed the single caloric performances. In particular for Ni-Mn-In, the maximum cyclic effect in magnetic fields of 1.9 T is increased by more than 200 % to -4.1 K when a moderate sequential stress of 55 MPa is applied. Our results illustrate the crucial role of microstructure for multicaloric cooling using Ni-Mn-based metamagnetic shape-memory alloys. [Display omitted] [ABSTRACT FROM AUTHOR]