On the electronic origin of the inverse magnetocaloric effect in Ni-Co-Mn-In Heusler alloys

In order to understand the electronic origin of the inverse magnetocaloric effect observed in a Ni-Co-Mn-In system we used a combination of indirect experimental probes as magnetization, resistivity and specific heat. The findings are compared with the band structure of isostructural Heusler alloys such as Ni-Mn-Ga. We suggest that the inverse magnetocaloric effect in Ni-Co-Mn-In originates from the high density of states close to Fermi energy. Within the austenite state this causes ferromagnetic band splitting. The structural change to the martensite allows an alternative way to reduce the high density of states at lower temperatures, which does not require band splitting and thus does not support ferromagnetic order.