Effect of Al doping on the magnetic, magneto-structural, and magnetocaloric properties of Ni-Mn-In Heusler alloys

The present study aimed at investigating the effect of Al doping (0-1.5 at. %) on the magnetic, magneto- structural, and magnetocaloric properties of the Ni50Mn34In16 Heusler alloy with diameters of 2 mm prepared using a suction-casting technique. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and magnetic force microscopy (MFM) were employed to identify the structure, microstructure, and magnetic domain distribution of the samples. Also, phase transformation behavior was characterized using differential scanning calorimetry (DSC) across a temperature range of 200-350 K. A SQUID Quantum Design MPMS (R) 3 was employed to evaluate the thermo-magnetic properties of the samples during heating and cooling cycles between 175 and 375 K under a constant magnetic field of 2 T. Finally, A cryostat-equipped vibrating sample magnetometer (VSM) was used to analyze the magnetic and magnetocaloric properties around the magneto-structural and magnetic phase transition temperature, up to a magnetic field of 1.75 T. Based on the results obtained, it was shown that doping 0.5 at. % Al increases magnetization, magnetic entropy change (GSM) and adiabatic temperature change (GTad) to 79 emu/g, 3.86 J/kg.K, and 1.14 K respectively, which can be attributed to the pre-martensitic phase transformation. However, by further Al substitution up to 1.5 at. %, the magneto-structural transformation temperatures shift toward higher values, while magnetization, G S M , and G T ad decrease.