Structural transformation and inverse magnetocaloric effect in Ni50Mn33In17

The structural and magnetic properties of Ni₅₀Mn₃₃In₁₇ were investigated by means of synchrotron X-ray diffraction and magnetization measurements. In contrast to well established critical concentration of $x\le 16.0$ for Ni₅₀Mn_50−xIn_x alloys to undergo structural transformation, we have found Ni₅₀Mn₃₃In₁₇ to undergo austenite to martensite structural transition around 170 K. At room temperature, the Rietveld refinement of X-ray diffraction measurements revealed a L2₁ Heusler cubic structure belonging to $\mathrm{Fm}3m$ space group while the low temperature martensite structure belongs to a monoclinic space group $P2/m$. Temperature dependent magnetization measurements confirmed a near room temperature paramagnetic to ferromagnetic magnetic transition as well as a magnetostructural transition at ∼170 K while magnetic field induced reverse martensite transformation was also confirmed. An inverse magnetocaloric effected associated with the magnetostructural transition is also observed with magnetic entropy change $\Delta S_M$ reaching ∼13.0 J/kg-K around 175 K under field change of 0–6 T. The inverse magnetocaloric effect occurs in a wide temperature range of 125–200 K with a relatively high refrigerant capacity of about 200 J/kg. This makes Ni₅₀Mn₃₃In₁₇ a promising magnetic refrigerant in the mentioned range of temperature as well as for further studies of effect of excess Mn on magnetic and structural properties of Ni₅₀Mn_50−xIn_x alloys.