Structural transformation and inverse magnetocaloric effect in Ni50Mn33In17

Abstract

Abstract 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 ≤ 16.0 for Ni50Mn50−xInx 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 Fm 3 m space group while the low temperature martensite structure belongs to a monoclinic space group P 2 / 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 Δ 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 Ni50Mn50−xInx alloys.