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

摘要

The structure, magnetic and martensitic properties of Fe doped Ni-Mn-Inmagnetic shape memory alloys have been studied by differential scanningcalorimetry, magnetization, resistivity, X-ray diffraction (XRD) and EXAFS.While Ni$_{2}$MnIn$_{1-x}$Fe$_{x}$ ($0 \le x \le 0.6$) alloys are ferromagneticand non martensitic, the martensitic transformation temperature inNi$_{2}$Mn$_{1.5} $In$_{1-y}$Fe$_{y}$ and Ni$_{2}$Mn$ _{1.6}$In$_{1-y}$Fe$_{y}$ increases for lower Fe concentrations ($y \le 0.05$) beforedecreasing sharply for higher Fe concentrations. XRD analysis reveals presenceof cubic and tetragonal structural phases in Ni$_{2}$MnIn$_{1-x}$Fe$_{x}$ atroom temperature with tetragonal phase content increasing with Fe doping. Eventhough the local structure around Mn and Ni in these Fe doped alloys is similarto martensitic Mn rich Ni-Mn-In alloys, presence of ferromagnetic interactionsand structural disorder induced by Fe affect Mn-Ni-Mn antiferromagneticinteractions resulting in suppression of martensitic transformation in these Fedoped alloys.