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

Abstract

The large change of unit cell volume at the martensitic transition of all-$d$-metal Heusler shape memory alloys suggests that these compounds are prone to exhibit a large barocaloric response. In this paper, the composition of a Ni-Mn-Ti alloy has been tailored so that it undergoes a martenistic transition between two structural phases which do not ferromagnetically order, thereby leading to a large transition entropy change. The combination of large entropy and volume changes confers to this alloy an outstanding barocaloric effect close to room temperature. The barocaloric performances found for the studied compound outperform those reported for other shape memory Heusler alloys, and are among the largest values reported for the best state-of-the-art intermetallic compounds. The reported results place all-$d$-metal Heusler shape memory alloys at the forefront of caloric materials to be used in clean solid-state refrigeration technologies.