Conventional and Inverse Magnetocaloric Effect in Ni-Rich Ni-Mn-Ga and Ni-Mn-Sn Heusler Alloy: A Comparison

Abstract

Magnetic and magnetocaloric effect of Ni-rich Ni₅₂Mn₃₄Sn₁₄ (Ni-Mn-Sn) and Ni₅₄Mn₁₇Ga₂₉ (Ni-Mn-Ga) Heusler alloys have been investigated up to a magnetic field of 5T and within a temperature range of 4.2 – 325 K. In this study, we report a systematic comparison between Ni-rich Ni₅₂Mn₃₄Sn₁₄ and Ni₅₄Mn₁₇Ga₂₉ alloys in the light of their magnetocaloric effect (MCE). In both the samples, a large magnetic entropy change was observed (~96 J kg^-1 K^-1  for Ni-Mn-Ga), but for the alloy Ni-Mn-Sn the MCE becomes negative/inverse. From various magnetic measurements it have been observed that in Ni-Mn-Sn alloy the martensite to austenite transition accompanied by lower to higher magnetization whereas for Ni-Mn-Ga alloy reverse situation occurred. The different type of magnetocaloric effect, i.e. inverse and direct can be explained by considering magneto-crystalline anisotropy and different state of magnetization of the martensite and austenite phase of the alloys.