Direct measurements of inverse magnetocaloric effects in metamagnetic shape-memory alloy NiCoMnIn

To clarify the electronic, lattice, and magnetic contribution to the inverse magnetocaloric effect (IMCE) in the metamagnetic shape-memory alloy Ni₄₅Co₅Mn_50-xInₓ, magnetization, magnetocaloric effect, and specific-heat measurements were carried out in a wide range of fields and temperatures. The IMCEs of Ni₄₅Co₅Mn36.7In13.3 were directly measured as adiabatic temperature changes in pulsed fields of up to 15 T. A maximum temperature decrease of -12.8 K was observed. The low-temperature specific heats in both the austenitic and the martensitic phases of Ni₄₅Co₅Mn36.5In13.5 were measured by using steady fields. Through analyses of the data, the entropy changes in charge (1.2 J/kg K), spin (-29 J/kg K), and lattice (51 J/kg K) sectors were individually evaluated. The result demonstrates the dominant role of the lattice sector in inverse MCEs in this material.