The effect of Al replacement and heat treatment on magnetocaloric properties of Ni2Mn–Sn ferromagnetic shape memory alloys

• We substituted Sn with Al for improving functional properties.
• We found higher magnetization and consequently better MCE in the systems.
• The property could be enhanced even more by optimizing the heat treatment.

We made a series of ferromagnetic shape memory alloys by large replacement of Sn in Ni2Mn1.36Sn0.64 system with Al to get good magnetocaloric effects. We studied this effect as a function of increase in amount of Al. While magnetocaloric property increased initially, it fell with higher contents of Al. To increase the effect at this Al concentration, we did secondary heat treatments at temperatures below the first annealing temperature. It was found that heat treatment can be used to tune the magnetism of the system, to obtain larger change in magnetization across the phase transformation, thus enhancing the functional capabilities of these alloys.