Effect of post-annealing on martensitic transformation and magnetocaloric effect in Ni45Co5Mn36.7In13.3 alloys

The metamagnetic alloy Ni45Co5Mn36.7In13.3 was fabricated by conventional arc-melting technique. Subsequent annealing may relax the stress and modify the atom ordering, thus influencing the magnetic properties and martensitic transformation behaviors. Our studies demonstrate that post-annealing at temperatures ≤ 300 °C can lead to a significant change in the magnetic properties and martensitic temperature (TM). Annealing the sample at 300 °C for 3 h can cause a decrease of as much as 30 K in TM (from 319 to 289 K) while retaining strong metamagnetic behaviors. The field-induced metamagnetic transition is accompanied with a large magnetocaloric effect. With an increase in the annealing temperature, the magnitude of the effective magnetic entropy change decreases somewhat, while the refrigeration capacity shows a slight increase.