Ferromagnetic interactions and martensitic transformation in Fe doped Ni-Mn-In shape memory alloys

The structure, magnetic, and martensitic properties of Fe doped Ni-Mn-In magnetic shape memory alloys have been studied by differential scanning calorimetry, magnetization, resistivity, X-ray diffraction (XRD), and EXAFS. While Ni2MnIn1−xFex (0 ≤ x ≤ 0.6) alloys are ferromagnetic and non martensitic, the martensitic transformation temperature in Ni2Mn1.5In1−yFey and Ni2Mn1.6In1−yFey increases for lower Fe concentrations (y ≤ 0.05) before decreasing sharply for higher Fe concentrations. XRD analysis reveals presence of cubic and tetragonal structural phases in Ni2MnIn1−xFex at room temperature with tetragonal phase content increasing with Fe doping. Even though the local structure around Mn and Ni in these Fe doped alloys is similar to martensitic Mn rich Ni-Mn-In alloys, presence of ferromagnetic interactions and structural disorder induced by Fe affect Mn-Ni-Mn antiferromagnetic interactions resulting in suppression of martensitic transformation in these Fe doped alloys.The structure, magnetic, and martensitic properties of Fe doped Ni-Mn-In magnetic shape memory alloys have been studied by differential scanning calorimetry, magnetization, resistivity, X-ray diffraction (XRD), and EXAFS. While Ni2MnIn1−xFex (0 ≤ x ≤ 0.6) alloys are ferromagnetic and non martensitic, the martensitic transformation temperature in Ni2Mn1.5In1−yFey and Ni2Mn1.6In1−yFey increases for lower Fe concentrations (y ≤ 0.05) before decreasing sharply for higher Fe concentrations. XRD analysis reveals presence of cubic and tetragonal structural phases in Ni2MnIn1−xFex at room temperature with tetragonal phase content increasing with Fe doping. Even though the local structure around Mn and Ni in these Fe doped alloys is similar to martensitic Mn rich Ni-Mn-In alloys, presence of ferromagnetic interactions and structural disorder induced by Fe affect Mn-Ni-Mn antiferromagnetic interactions resulting in suppression of martensitic transformation in these Fe doped alloys.