Giant magneto-caloric effect near room temperature in Ni-Mn-Sn-Ga alloys

TL;DR

This study reports a giant magneto-caloric effect near room temperature in Ni-Mn-Sn-Ga alloys, with significant entropy change observed across different compositions, highlighting their potential for magnetic refrigeration applications.

Contribution

The paper demonstrates a large magneto-caloric effect in Ga-doped Ni-Mn-Sn alloys near room temperature, with detailed analysis of how Ga concentration influences the transition temperature and entropy change.

Findings

Maximum entropy change of 13.6 J/kg K at 249 K for x=0.28

Significant MCE observed over a broad temperature range

Ga doping tunes the martensitic transition temperature

Abstract

We report the observation of giant magneto-caloric effect (MCE) in ferromagnetic shape memory alloys (FSMAs) of nominal compositions Ni$_2$Mn$_{1.36}$Sn$_{0.64-x}$Ga$_{x}$ ($x$ =0.24, 0.28 and 0.32). Irrespective of the Ga doping, all the samples undergo long range ferromagnetic ordering below around 330 K. However, the martensitic transition temperature ($T_{MS}$) of the samples varies strongly with Ga concentration. Clear signature of field induced transition around $T_{MS}$ is visible for all the samples. The observed MCE ($\Delta S$ = 13.6 J/kg K for field changing from 0 to 50 kOe) is found to be highest for $x$ = 0.28 with peak near 249 K, while $x$ = 0.32 shows $\Delta S$ = 12.8 J/kg K at 274 K. This series of Ga-doped alloys are found to be interesting materials with high value of $\Delta S$ over a varied range of temperature