Tuning the magnetocaloric properties of the Ni2+xMn1-xSn Heusler alloys

We report the effect of Ni substitution on the magnetic properties of polycrystalline Ni2+xMn1-xSn (x = 0, 0.05, and 0.1) Heusler alloys using the magnetization and neutron diffraction measurement techniques. The paramagnetic to ferromagnetic transition temperature (Curie temperature, T-C) has been tuned with the substitution of Ni at the Mn sites (T-C approximate to 349, 337, and 317 K for x = 0, 0.05, and 0.1 samples, respectively) without a significant reduction in the magnetic entropy change -Delta S-M. For a magnetic field change from 0 to 5 T, -Delta S-M of 2.9, 2.5, and 2.2 J kg(-1) K-1 have been observed for x = 0, 0.05, and 0.1 samples, respectively. From the neutron diffraction study, it has been found that with increasing x, the Mn site ordered moment decreases. -Delta S-M as a function of changing magnetic field and Curie temperature follows the molecular mean field model. The studied Ni2+xMn1-xSn alloys, with their nontoxic constituent elements and low-cost, can be used for magnetic cooling over a wide temperature range of 278-379 K covering room temperature. (C) 2013 AIP Publishing LLC.