Strain glass versus antisite disorder induced ferromagnetic state in Fe doped Ni–Mn–In Heusler martensites

Fe doping in Ni₂Mn_1.5In_0.5 results in suppression of the martensitic phase via two contrasting routes. In Ni₂Mn_{1.5 − x}Fe_xIn_0.5, the martensitic phase is converted to a strain glassy phase, while in Ni_2 − yFe_yMn_1.5In_0.5, a cubic ferromagnetic phase results at the expense of the martensite. Careful studies of magnetic and structural properties reveal the presence of the impurity γ-(Fe,Ni) phase as the reason for the emergence of non-ergodic strain glassy phase when Fe is sought to be doped at Y/Z (Mn) sites of X₂YZ Heusler alloy. Whereas attempts to dope Fe in the X (Ni) sublattice result in an A2 type antisite disorder that promotes a ferromagnetic ground state. (paper)