| Summary: | Structural, microstructural, and magnetic properties of Heusler Ni<sub>50</sub>Mn<sub>50−x</sub>In<sub>x</sub> (x = 5 and 10) ribbons have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), differential scanning calorimetry (DSC), and vibrating sample magnetometry (VSM). The as quenched Ni<sub>50</sub>Mn<sub>45</sub>In<sub>5</sub> ribbons exhibit a mixture of monoclinic <i>14M</i> (a = 4.329(3) Å, b = 5.530(3) Å, and c = 28.916(3) Å), and tetragonal <i>L1</i><sub>0</sub> (a = b = 3.533(3) Å, and c = 7.522(3) Å) martensite structures, while Ni<sub>50</sub>Mn<sub>40</sub>In<sub>10</sub> ribbons display a single monoclinic <i>14M</i> phase (a = 4.262(3) Å, b = 5.692(3) Å, and c = 29.276(3) Å). After three heating/cooling cycles, in the temperature range of 303–873 K, the Rietveld refinement of the XRD patterns revealed the presence of a single <i>14M</i> martensite for Ni50Mn45In5 ribbons, and a mixture of cubic <i>L2</i><sub>1</sub> (31%) and <i>14M</i> (69%) phases for Ni<sub>50</sub>Mn<sub>40</sub>In<sub>10</sub> ribbons. The characteristic temperatures of the martensitic transition (<i>A<sub>start</sub></i>, <i>A<sub>finish</sub></i>, <i>M<sub>start</sub></i>, and <i>M<sub>finish</sub></i>), the thermal hysteresis temperature width, and the equilibrium temperature decreased with increasing indium content and heating cycles. The samples show a paramagnetic like behavior in the as quenched state, and a ferromagnetic like behavior after the third heating/cooling cycle.
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