Magnetocaloric effect in Ni2(Mn,Cu)Ga0.84Al0.16 Heusler alloys

•High values of entropy change (ΔS) under relatively low magnetic fields.•Large magnetic-field-induced ΔS between ferromagnetic structures.•A magnetostructural transformation with ΔS = −12.6 Jkg−1K−1 at 300 K for 0–1 T. Polycrystalline Heusler compounds Ni2Mn0.75Cu0.25Ga0.84Al0.16, with a martensitic transition between ferromagnetic phases, and Ni2Mn0.70Cu0.30Ga0.84Al0.16, with a magnetostructural transformation, were investigated by magnetization and heat capacity measurements, both as a function of temperature and magnetic field. The compound Ni2Mn0.75Cu0.25Ga0.84Al0.16 presents a large magnetocaloric effect at a transition between magnetically aligned structures. In addition, Ni2Mn0.70Cu0.30Ga0.84Al0.16 shows very high entropy change at room temperature, although irreversible, under a magnetic field change 0–1 T. The magnetocaloric properties of the studied samples are compared with selected compounds in the literature.