Ni-Mn-$X$ ($X=\mathrm{In}$, Sn, and Sb) based Heusler alloys show a strong potential for magnetic refrigeration owing to their large magnetocaloric effect (MCE) associated with first-order magnetostructural transition. However, the irreversibility of the MCE under low field change of 0–1 T directly hinders its application as an efficient magnetic coolant. In this work, we systematically investigate thermal and magnetic properties, crystalline structure and magnetocaloric performance in $\mathrm{N}{\mathrm{i}}_{51-x}\mathrm{M}{\mathrm{n}}_{33.4}\mathrm{I}{\mathrm{n}}_{15.6}{\mathrm{V}}_x$ alloys. With the introduction of V, a stable magnetostructural transition near room temperature is observed between martensite and austenite. An extremely small hysteresis of 2.3 K is achieved for the composition $x=0.3$. Due to this optimization, the magnetic-field induced structural transition is partially reversible under 0–1 T cycles, resulting in a reversible MCE. Both magnetic and calorimetric measurements consistently show that the largest value for the reversible magnetic entropy change can reach about $5.1\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$ in a field change of 0–1 T. A considerable and reversible adiabatic temperature change of −1.2 K by the direct measurement is also observed under a field change of 0–1.1 T. Furthermore, the origin of this small hysteresis is discussed. Based on the lattice parameters, the transformation stretch tensor is calculated, which indicates an improved geometric compatibility between the two phases. Our work greatly improves the MCE performance of Ni-Mn-$X$-based alloys and make them suitable as realistic magnetic refrigeration materials.

• Received 24 May 2019

DOI:https://doi.org/10.1103/PhysRevMaterials.3.084409