Synergic Improvement of Elastocaloric Effect in Polycrystalline NiMnGaCo by Magneto-Mechanical Coupling

Among the ferromagnetic shape memory alloys (SMAs), Ni43Mn31Ga19Co7 (at%) alloys are well known as a promising ferromagnetic SMA (FeSMA) for magnetocaloric effect, and scientific interest has increased due to the possible exploitation of multicaloric function. This first example of multi-effect by coupling elastocaloric and magnetocaloric effect is still far from complete experimental validation, mainly due to the difficulty of testing conditions that require the simultaneous application of both fields. In this study, a low magnetic field (μ₀H = 0.26 T and 0.56 T) is applied during elastocaloric deformation at different temperatures. Although the magnetic field values applied in this work are much lower than those usually considered in the magnetocaloric effect, the magnetic field improves the elastocaloric effect, increasing the total strain and reducing the critical stress and mechanical hysteresis. This synergic action allows us to obtain an increase in the ΔT_ad of about 13% and 25% upon loading and unloading, respectively.