Giant barocaloric effect in all-d-metal Heusler shape memory alloys

We have studied the barocaloric properties associated with the martensitic transition of a shape memory Heusler alloy Ni50Mn31.5Ti18.5 which is composed of all-d-metal elements. The composition of the sample has been tailored to avoid long-range ferromagnetic order in both austenite and martensite. The lack of ferromagnetism results in a weak magnetic contribution to the total entropy change, thereby leading to a large transition entropy change. The combination of such a large entropy change and a relatively large volume change at the martensitic transition gives rise to giant barocaloric properties in this alloy. When compared to other shape memory Heusler alloys, our material exhibits values for adiabatic temperature and isothermal entropy changes significantly larger than values reported so far for this class of materials. Furthermore, our Ni50Mn31.5Ti18.5 also compares favorably to the best state-of-the-art magnetic barocaloric materials