Effect of the Solidification Rate on the Magnetic, Magnetocaloric, and Magneto-Structural Properties of Nimnin Heusler Alloy

Abstract

In this work, an attempt is made to study the effects of solidification rate on the magnetic, magnetocaloric, and magneto-structural properties of stoichiometric Ni50Mn34In16 Heusler alloy. In this respect, bulk samples with two different diameters of 2 mm (D2 sample) and 8 mm (D8 sample) were prepared by suction-casting technique and subjected to annealing for 4 hours at a temperature of 1073 K. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), magnetic force microscopy (MFM) and differential scanning calorimetry (DSC) were used to investigate their structural and phase transformation behavior of the samples. The magnetic and magnetocaloric properties of the samples were conducted using SQUID Quantum Design MPMS®3 during heating and cooling in the temperature range of 175-350K. Based on the results obtained, it was shown that the solidification rate plays an important role in the control of phase transformation and activation energy. It was found that by decreasing the solidification rate, the activation energy increased from 102.42 kJ/mol for the D2 sample to 110.252 kJ/mol for the D8 sample. The maximum magnetization is evaluated as 42.5 emu/gr for the D2 sample and 48.8 emu/gr for the D8 sample under a magnetic field of 1.8 T. As well as, the magnetocaloric properties were improved due to decreasing of the solidification rate, so that, the maximum values of magnetic entropy change (ΔSM) and refrigerant capacity (RC) for the D8 sample were estimated 3.58 J/kg.K and 159.48 J/kg near room temperature respectively.

Keywords: Solidification rate, NiMnIn Heusler alloy, magnetic properties, magnetocaloric effect, magneto-structural transformation