Effect of the Solidification Rate on the Magnetic and Magnetocaloric Properties of NiMnIn Heusler Alloy: Second-Order Magnetic Transition

This work attempted to study the effects of the solidification behavior on the magnetic and magnetocaloric properties of stoichiometric Ni₅₀Mn₃₄In₁₆ Heusler alloy. In this respect, the samples with two different diameters of 2 mm (D2 sample) and 8 mm (D8 sample) were prepared by suction casting technique. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), 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. Thermo-magnetic properties of samples were evaluated using SQUID Quantum Design MPMS®3 during heating and cooling at the temperature range of 175–350 K at the constant magnetic field of 2 T. Moreover, the magnetic and magnetocaloric properties of the samples were analyzed using the cryostat-equipped VSM around the magnetic phase transition temperature under a magnetic field up to 1.75 T. Based on the results obtained, it is shown that an increase in the sample diameter leads to an increase in the Curie temperature. Furthermore, it was concluded that the magnetocaloric properties such as magnetic entropy change ( \(\Delta {S}_{\text{M}}\) $\mathrm{\Delta }{S}_{\text{M}}$ ), adiabatic temperature change ( \(\Delta {T}_{\text{ad}}\) $\mathrm{\Delta }{T}_{\text{ad}}$ ), and refrigerant capacity ( \(RC\) $\mathit{RC}$ ) parameters improved with an increase in the sample diameter through the microstructural refinement and enhancing the atomic ordering. Specifically, the maximum values of the \(\Delta {S}_{\text{M}}\) $\mathrm{\Delta }{S}_{\text{M}}$ , \(RC\) $\mathit{RC}$ , and \(\Delta {T}_{\text{ad}}\) $\mathrm{\Delta }{T}_{\text{ad}}$ for the D8 sample are estimated to be 3.04 J/kg K, 109.83 J/kg, and 0.94 K, respectively.