Tuning the magnetocaloric properties of the Ni_2+xMn_1-xSn Heusler alloys

Abstract

We report the effect of Ni substitution on the magnetic properties of polycrystalline Ni_2+xMn_1-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 ≈ 349, 337, and 317 K for x = 0, 0.05, and 0.1 samples, respectively) without a significant reduction in the magnetic entropy change −ΔS_M. For a magnetic field change from 0 to 5 T, −ΔS_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. −ΔS_M as a function of changing magnetic field and Curie temperature follows the molecular mean field model. The studied Ni_2+xMn_1-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.