Mössbauer study of atomic order inNi3Fe. II. The order-disorder transition

The structural order-disorder reactions in stoichiometric ${\mathrm{Ni}}_3$Fe were followed "at temperature" using Mössbauer spectroscopy. The transition is of first order. Near the transition temperature $T_D$ the transformation proceeds via nucleation and growth and a two-phase region is observed. In a hysteresis zone below this region the nucleation of the ordered phase is suppressed. This is explained on basis of magnetic interactions. Away from $T_D$ both the ordering and the disordering reactions proceed homogeneously. Upon approach of $T$ to $T_D$, the kinetics of both reactions slow down.