Achievement of a reversible giant magnetocaloric effect via exerting external hydrostatic pressure on a Ni₄₅Co₅Mn₃₅In₁₅ metamagnetic Heusler alloy

Magnetocaloric materials with first-order phase transition are potential refrigerant media for solid state refrigeration. In this work, the Ni₄₅Co₅Mn₃₅In₁₅ alloy possesses a representative first-order martensitic transition (MT), which is found to be sensitive to both magnetic field and isostatic pressure with rates of ∼−6.4 K T⁻¹ and ∼4.24 K kbar⁻¹. Such an active response to multi-stimuli derives from the strong coupling of the spin and the lattice. A low magnetic field of 1 T can drive nearly 100% of the total entropy change corresponding to the whole transformation in this alloy. However, the prominent magnetocaloric effect (MCE) is almost irreversible owing to the intrinsic hysteresis of the first-order phase transition. By virtue of the strong magnetostructural coupling during the MT, a hydrostatic pressure assisted magnetic field loading loop has been constructed for eliminating the hysteresis and to a large extent improve the reversibility of the MCE. (paper)