External‐field‐induced phase transformation and associated properties in a ni₅₀mn₃₄fe₃in₁₃ metamagnetic shape memory wire

Metamagnetic shape memory alloys exhibit a series of intriguing multifunctional properties and have great potential for applications in magnetic actuation, sensing and magnetic refrigeration. However, the poor mechanical properties of these alloys with hardly any tensile deformability seriously limit their practical application. In the present work, we developed a Ni‐Fe‐ Mn‐In microwire that exhibits both a giant, tensile superelasticity and a magnetic‐field‐induced first‐order phase transformation. The recoverable strain of superelasticity is more than 20% in the temperature range of 233–283 K, which is the highest recoverable strain reported heretofore in Ni‐ Mn‐based shape memory alloys (SMAs). Moreover, the present microwire exhibits a large shape memory effect with a recoverable strain of up to 13.9% under the constant tensile stress of 225 MPa. As a result of the magnetic‐field‐induced first‐order phase transformation, a large reversible magnetocaloric effect with an isothermal entropy change ΔSm of 15.1 J kg⁻¹ K⁻¹ for a field change from 0.2 T to 5 T was achieved in this microwire. The realization of both magnetic‐field and tensile-stress‐induced transformations confers on this microwire great potential for application in miniature multi‐functional devices and provides an opportunity for multi‐functional property optimization under coupled multiple fields.