Influence of copper substitution on the magnetic and magnetocaloric properties of NiMnInB alloys

The structural, magnetocaloric, and thermomagnetic properties of Ni50.51Mn34.34−xCuxIn14.14B1.01 with x = (0, 1.26, and 2.02) have been studied using room-temperature x-ray diffraction, differential scanning calorimetry (DSC), and magnetization measurements. The partial substitution of Cu for Mn was found to shift both the martensitic transition temperature (TM) and the Curie temperature (TC) to lower temperatures. The values of the latent heat (L = 9.4 J/g) and corresponding magnetic (ΔSM) and total entropy (ΔST) changes (ΔSM = 22.60 J/kg K for ΔH = 5 T and ΔST = 29.7 J/kg K) have been evaluated using magnetic and DSC measurements, respectively, for the sample with x = 1.26. Large negative values of ΔSM of −7.27 and −5.98 J/kg K for ΔH = 5 T in the vicinity of TC were observed for x = 1.26 and 2.02, respectively. It has been found that the application of hydrostatic pressure changes the magnetic ground state of the martensitic phase and increases the temperature stability of the martensitic phase. The roles of the magnetic and structural changes on the transition temperatures are discussed.